10-K

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The aggregate market value of the voting stock held by non-affiliates of the registrant, as of June 30, 2024, was $69.0 million. Such aggregate market value was computed by reference to the closing price of the common stock as reported on the Nasdaq Global Select Market on June 30, 2024. For purposes of making this calculation only, the registrant has defined affiliates as including only (1) directors, (2) executive officers and (3) certain stockholders, if any, that hold greater than 10% of the voting stock of the registrant, in each case, as of June 30, 2024. Shares of common stock held by other persons, including certain other holders of more than 10% of the registrant’s outstanding common stock, if any, have not been excluded from the above calculation in that such persons are not deemed to be affiliates. The determination of affiliate status is not necessarily a conclusive determination for other purposes.

As of March 14, 2025, there were 7,503,385 shares of the registrant’s common stock, $0.001 par value per share, outstanding.

Throughout this Annual Report on Form 10-K, the “Company,” “Assembly Bio,” “Assembly,” “we,” “us,” and “our,” except where the context requires otherwise, refer to Assembly Biosciences, Inc. and its consolidated subsidiaries, and “our board of directors” or “the Board” refers to the board of directors of Assembly Biosciences, Inc.

This Annual Report on Form 10-K contains “forward-looking statements” that are subject to certain risks and uncertainties, including, without limitation, those set forth in Part I, Item 1A under the heading “Risk Factors,” that could cause actual results to materially differ. Such risks and uncertainties include, among other things:

You are urged to consider statements that include the words may, will, would, could, should, might, believes, hopes, estimates, projects, potential, expects, plans, anticipates, intends, continues, forecast, designed, goal or the negative of those words or other comparable words to be uncertain and forward-looking. In particular, forward-looking statements include, but are not limited to, statements regarding the timing of commencement of future clinical studies involving our therapeutic product candidates; and our ability to successfully complete, and receive favorable results in, clinical studies for our product candidates. We intend such forward-looking statements to be covered by the safe harbor provisions contained in Section 27A of the Securities Act of 1933, as amended (the Securities Act), and Section 21E of the Securities Exchange Act of 1934, as amended (the Exchange Act). Except as required by law, we assume no obligation to update publicly any forward-looking statements, whether as a result of new information, future events or otherwise.

We are a biotechnology company developing innovative therapeutics targeting serious viral diseases with the potential to improve the lives of patients worldwide. Our pipeline includes multiple clinical-stage investigational therapies, including: (1) two helicase-primase inhibitors (HPI) targeting recurrent genital herpes; (2) an orally bioavailable hepatitis delta virus (HDV) entry inhibitor; and (3) a highly potent next-generation capsid assembly modulator (CAM) designed to disrupt the replication cycle of hepatitis B virus (HBV) at several key points. Our pipeline also includes a novel, oral broad-spectrum non-nucleoside polymerase inhibitor (NNPI) targeting transplant-related herpesviruses, which is currently undergoing studies to enable a regulatory filing, and we have additional research programs against multiple antiviral targets.

Our current business strategy focuses on applying our deep research and development expertise in virology to bring next-generation therapeutics to patients in areas of high unmet medical need and significant market opportunities and rapidly advance our portfolio towards near-term clinical readouts:

We have recruited an accomplished leadership team and research and development organization, with a collective team track record of over 15 approved drugs across multiple viral diseases. Our collaboration with Gilead Sciences, Inc. (Gilead and the Gilead Collaboration) also brings us an industry-leading partner and brings together the teams’ expertise in virology and provides an established partner for late-stage development and commercialization. For additional information regarding the Gilead Collaboration, see “Collaboration and License Agreements—Gilead Sciences, Inc.”

Since the beginning of 2024, we have initiated: (1) both the Phase 1a and Phase 1b portions of a Phase 1a/b study of 5366, long-acting HPI for recurrent genital herpes; (2) the Phase 1a portion of a Phase 1a/b study of 1179, also a long-acting HPI for recurrent genital herpes; (3) a Phase 1a study of 6250, an orally bioavailable HDV entry inhibitor; and (4) a Phase 1b study of 4334, a highly potent, next-generation CAM for chronic HBV infection. We expect to initiate the Phase 1b portion of the Phase 1a/b study of 1179 in the first half of 2025.

We announced interim results from the Phase 1a portion of the 5366 study in September 2024, interim results from the Phase 1b study of 4334 in December 2024 and interim results from the Phase 1a portion of the 1179 study in February 2025.

In addition, during December 2024, we identified a development candidate, 7423, in our broad-spectrum NNPI program targeting transplant-associated herpesviruses.

Genital herpes can be caused by either herpes simplex virus type 1 (HSV-1) or herpes simplex virus type 2 (HSV-2). HSV-1 and HSV-2 are acquired by oral or genital contact either during symptomatic or asymptomatic reactivation of the virus. Both viruses replicate in neurons, where they can remain latent for the rest of the individual’s life and periodically reactivate, with the virus spreading, replicating and causing disease in epithelial tissues. Initial infection can be asymptomatic or can be marked by serious symptoms, including painful skin lesions, swelling of lymph nodes and urinary problems that can persist for two to three weeks. While genital herpes can be caused by either HSV-1 or HSV-2, recurrences are more likely to be experienced by individuals infected by HSV-2. Genital herpes recurrence can cause painful genital lesions that can lead to increased transmission and debilitate patients, and symptoms may become more serious with additional episodes. Additional complications include increased risk of HIV infection, as 30% of HIV infections acquired through sexual transmission are attributable to HSV-2 infection. In addition, people with recurrent genital herpes often experience associated psychosocial impacts, including anxiety, concerns about transmission, depression and social stigma. Immunocompromised patients may experience more severe and prolonged symptoms due to increased recurrence rates.

HPIs are antiviral agents in development for the treatment of recurrent genital herpes, with a clinically-validated mechanism of action. HPIs inhibit the HSV helicase-primase complex, which is a unique viral enzyme complex without a human homolog, consisting of helicase, primase and cofactor subunits. These subunits have functions that are essential for viral DNA replication and are conserved across HSV-1 and HSV-2. Unlike nucleoside analogs, these compounds do not require phosphorylation by the HSV thymidine kinase (TK) and ongoing viral replication to become active drugs. As a result, HPIs are active immediately upon reactivation of latent HSV-1 and HSV-2. Furthermore, HPIs are active against TK-deficient HSV-1 and HSV-2, which is a major mechanism of resistance to nucleoside analogs.

Most people with initial symptomatic genital herpes who are infected with HSV-2 have frequent recurrences, generally between three and 15 per year, including over four million people in the United States and France, Germany, Italy and Spain (collectively, the EU4) and the United Kingdom (UK). Currently, there are three antiviral drugs (all nucleoside analogs) that have been approved in the United States and the EU4/UK for the treatment of genital herpes. However, no new drugs have been approved in these regions to treat genital herpes for more than 25 years. In addition to the approved nucleoside analogs, agents such as local anesthetics or analgesics may be used to alleviate local symptoms of minor pain and discomfort.

Nucleoside analogs can be administered as episodic therapy as individual outbreaks arise or daily as chronic suppressive therapy for those with high post-exposure recurrences. However, these agents are only partially effective at controlling the infection or reducing transmission risk. With current nucleoside analog therapies, only one out of three people with recurrent genital herpes with six or more recurrences per year are able to make it through a year of treatment without a recurrence. There are still high titer (greater than 104 HSV-2 DNA copies/mL) shedding episodes under this current standard of care for recurrent genital herpes, which can lead to recurrent episodes and transmission of genital herpes.

Based on the limitations of current therapies, we see a path to advancing the treatment paradigm for people suffering from recurrent genital herpes. To reach that goal, we discovered and are developing a novel, potent, long-acting HPI for recurrent genital herpes, 5366, which demonstrated low nanomolar potency in vitro against both HSV-1 and HSV-2 clinical isolates and a favorable nonclinical safety profile in the U.S. Food and Drug Administration's (FDA) Good Laboratory Practice (GLP) toxicology studies, with high safety margins and minimal potential for off-target effects. In addition, we are developing a second novel, potent, long-acting HPI for genital herpes, 1179, which was in-licensed to us as part of our collaboration with Gilead.

During the first quarter of 2024, we filed a Clinical Trial Application (CTA) to support initiation of a Phase 1a/b clinical study for 5366, which was approved in April 2024, and we dosed our first participant in the Phase 1a portion of this study during the second quarter of 2024.

In September 2024, we announced positive interim data for the Phase 1a portion of the 5366 study. Interim results exceeded our objectives for this Phase 1a study and support 5366’s progression into Phase 1b, which we initiated during the third quarter of 2024. Across the Part A (Phase 1a) cohorts evaluated, 5366 had a mean half-life of approximately 20 days when dosed orally, supporting once-weekly oral dosing, the target profile for 5366, as well as showing the potential for once-monthly oral dosing. We plan to explore both once-weekly and once-monthly oral dosing regimens in the Part B (Phase 1b) portion of the study.

In the Part A cohorts, 5366 has been well-tolerated with a favorable safety profile observed with exposure of up to 70 days. Treatment-emergent adverse events (AEs) were all mild to moderate in intensity and all were considered not related to study treatment by the study investigators; there have been no serious AEs in any dose arm. There were no treatment-related Grade 3 or 4 laboratory abnormalities and no protocol-defined stopping criteria were met. There were no clinically significant electrocardiogram (ECG) abnormalities or patterns of AEs or laboratory abnormalities noted.

We expect interim data from the Phase 1b portion of the 5366 study to be available in fall 2025.

In addition to 5366, we are also advancing 1179, a structurally-differentiated HPI with single digit nanomolar potency against HSV-1 and HSV-2 and a nonclinical PK and safety profile to date that is supportive of a potential long-acting treatment by once-weekly oral administration. We submitted the CTA for a Phase 1a/b study of 1179 in September 2024, which was approved in October 2024. We dosed our first participant in the Phase 1a portion of this study during the fourth quarter of 2024.

In February 2025, we announced positive interim data for the Phase 1a portion of the 1179 study. Interim results exceeded our objectives for this Phase 1a study and support 1179’s progression into Phase 1b, and we plan to move directly into the Phase 1b study in participants with recurrent genital herpes. Across the Part A (Phase 1a) cohorts evaluated as of the February 13, 2025 data cutoff date, 1179 had a mean half-life of approximately four days when dosed orally, supporting once-weekly oral dosing, the target profile for 1179.

In all cohorts as of the February 13, 2025 data cutoff date, 1179 has been well-tolerated with a favorable safety profile observed. Treatment-emergent AEs were all mild in intensity and all were considered not related to study treatment by the study investigators; there have been no serious AEs in any dose cohort. One self-limited Grade 2 alanine transaminase elevation was observed in a cohort evaluating the highest dose of 300 mg. There were no treatment-related Grade 3 or 4 laboratory abnormalities and no protocol-defined stopping criteria were met. There were no clinically significant ECG abnormalities or patterns of AEs or laboratory abnormalities noted. We expect interim data from the Phase 1b portion of the 5366 study to be available in fall 2025.

The Phase 1b study of 1179 study will be conducted concurrently with the ongoing Phase 1b evaluation of 5366, our other long-acting helicase-primase inhibitor candidate that began dosing in Phase 1b in the fourth quarter of 2024. The studies are anticipated to be conducted at the same sites using equivalent eligibility criteria and outcome measures for both candidates. We plan to report interim data for both candidates together in fall 2025.

The World Health Organization (WHO) estimates that 254 million people worldwide are chronically infected with HBV as of 2022, and 1.2 million new infections occur each year. HBV is a leading global cause of chronic liver disease and liver transplants, and the WHO estimates that 1.1 million people died in 2022 from HBV, mostly due to cirrhosis and hepatocellular carcinoma. As of 2022, of the 254 million people living with chronic HBV infection, only approximately 33 million, or 13%, were aware of their infection, and only approximately 7 million, or 3%, of those diagnosed received treatment. HBV is a highly prevalent disease that infects almost three times the number of people infected with hepatitis C virus and HIV infections combined, according to the WHO.

The current standard of care for chronic HBV infection, nucleos(t)ide analog reverse transcriptase inhibitors (NrtIs), are taken life-long and reduce, but do not eliminate, the virus and result in very low cure rates. No new mechanisms of action (MOA) have been approved for the treatment of chronic HBV infection in over 25 years. The focus of our HBV program is to improve outcomes and increase the number of patients diagnosed and treated through the development of finite and curative therapies targeting an orthogonal MOA.

HDV is a “satellite virus” of HBV because it can only infect people (1) who are already infected with HBV or (2) at the same time as a person is infected with HBV. HDV affects a subset of approximately 12 to 72 million HBV infected people. These individuals infected with HDV, which comprise an estimated 4.5% of hepatitis B surface antigen (HBsAg) positive individuals, experience a substantially increased disease burden, as they account for 18% of cirrhosis and 20% of hepatocellular carcinoma associated with HBV. HDV is considered the most severe form of hepatitis, as 70% of individuals infected with HDV progress to cirrhosis within ten years. While HDV is less prevalent in the United States, it is a significant and serious health problem with inadequate treatment in many parts of Europe, Africa, the Middle East, East Asia and parts of South America. HDV may be significantly underdiagnosed, because there were no HDV-targeted therapies approved until very recently, and the first therapy approved is only approved in Europe. HDV is known to accelerate disease progression and increase the incidence of liver cirrhosis and liver cancer, which results in higher morbidity and mortality rates than HBV alone.

The current standard of care treatment for HDV is off-label pegylated interferon-α (IFN-α) injected weekly or, in Europe, a large, complex peptide inhibitor that requires daily injections, bulevirtide. There are no approved HDV treatments in the United States, and the large, complex peptide blocker is the only approved HDV treatment in the Europe. We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for people living with HDV, who face a significant and immediate disease burden.

HDV is a small RNA virus that encodes just two viral proteins and relies on host enzymes as well as the HBsAg from HBV to replicate, which limits the number of HDV-specific antiviral targets. Similar to HBV, HDV utilizes HBsAg to enter hepatocytes by binding the cellular transmembrane protein sodium taurocholate co-transporting peptide (NTCP). NTCP is highly expressed on human hepatocytes, where it serves as one of several proteins involved in the transport of bile acids. The binding of specific small or large molecules to NTCP has been shown to effectively inhibit the interaction of HBsAg with NTCP, which prevents HBV and HDV from infecting hepatocytes.

The inhibition of HBV and HDV infection by molecules that bind NTCP has been demonstrated in vitro, in animal models and clinically. Notably, bulevirtide, a peptide blocker of NTCP, is the only approved therapy for HDV (approved in Europe). 6250 uses the same clinically-validated MOA as bulevirtide. The binding of NTCP-targeted HBV/HDV entry inhibitors to NTCP has also been shown to inhibit the transport of certain bile acids into cells, which results in plasma elevations of bile acids; this effect has been well-tolerated clinically and may serve as a biomarker of pharmacologically active concentrations of drug in the plasma. In nonclinical studies in non-human primates, clinically-relevant doses of 6250 elevated bile acids to levels similar to those seen in humans with bulevirtide.

We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for people living with HDV and could significantly improve treatment uptake and diagnosis rates, especially when compared with currently available injectable products.

In September 2023, we nominated 6250, a novel, orally bioavailable small molecule designed to inhibit entry of HBV and HDV by targeting NTCP. In nonclinical studies, 6250 demonstrated low nanomolar potency against all tested HBV/HDV genotypes, favorable selectivity for NTCP versus other bile acid transporters, good oral bioavailability and a PK profile in nonclinical species projected to support once-daily oral dosing. In GLP toxicology studies, 6250 demonstrated a favorable nonclinical safety profile with wide safety margins.

At the European Association for the Study of the Liver's International Liver CongressTM in June 2024 and the International HBV Meeting in September 2024, we presented nonclinical profiling of 6250. In addition, 6250 was featured in an oral presentation at the Science of HBV Cure Meeting 2024. We initiated a Phase 1a clinical study of 6250 during the fourth quarter of 2024, and we expect interim safety, PK and biomarker data from single-ascending and multiple-ascending doses cohorts in healthy participants in the third quarter of 2025.

we have worked to discover and develop compounds targeting the core protein, a viral protein involved in numerous aspects of the HBV replication cycle, including the generation of HBV cccDNA.

A benchmark for therapeutic agents aiming to decrease cccDNA levels is the use of several key viral antigens as surrogate biomarkers of active cccDNA. The same biomarkers can be used in both primary human hepatocytes and infected individuals. On this basis, our next-generation CAM, 4334, has shown nonclinical proof of principle. In a variety of cell culture models, 4334 has demonstrated the ability to reduce production of HBV DNA levels as well as the surrogate markers for cccDNA establishment: HBV e antigen (HBeAg), HBV core-related antigen (HBcrAg) and HBV pre-genomic RNA (pgRNA).

As a next-generation CAM, 4334 was optimized to potently disrupt viral replication (MOA #1) and prevent the establishment and replenishment of new cccDNA (MOA #2). In contrast, while active against MOA #1, first-generation CAMs have not demonstrated adequate potency to sufficiently block cccDNA formation (MOA #2). Further, the current standard of care, NrtIs, impacts the viral life cycle after establishment of cccDNA and can only inhibit production of new viral particles, and it does so incompletely. The chemical scaffold of 4334 is novel and distinct from all our prior CAM candidates.

We believe that 4334 has a best-in-class nonclinical profile, with single-digit nanomolar potency against MOA #1 and MOA #2, pan-genotypic activity, an improved resistance profile and a favorable safety profile. Through mechanistic studies presented at multiple conferences, we have demonstrated that 4334 promotes the formation of empty capsids by acceleration of capsid assembly, prevents the formation of cccDNA by disrupting incoming capsids, and prematurely disrupts capsids containing duplex linear DNA, the precursor for integrated HBV DNA.

A Phase 1a study demonstrated that 4334 was well-tolerated when administered orally as single or multiple doses. In addition, the PK data support 4334 as a once daily oral therapy and predicts best-in-class activity against both MOA #1 and MOA #2. During the second quarter of 2024, we dosed our first participant in a Phase 1b clinical study of 4334. We reported interim clinical results from the initial 150 mg cohort in December 2024, which indicated that 4334 maintained clinical exposures multiple folds above those anticipated to be required for potent viral activity and inhibition of cccDNA formation. A mean decline in HBV DNA of 2.9 log10 IU/mL was observed in a population of predominately HBeAg negative participants. Among the subset of participants with detectable HBV RNA at baseline, a mean decline of 2.5 log10 U/mL for HBV RNA was observed. As anticipated, limited changes in viral antigens were observed for the study population over the 28-day treatment period. These initial antiviral data are consistent with the high potency seen preclinically for 4334. The interim safety data also demonstrated that 4334 was well-tolerated with a favorable safety profile observed. Enrollment is ongoing for the second cohort, evaluating an oral once-daily 400 mg dose of 4334. Based on the strong antiviral activity observed in the first cohort, we expect that the 400 mg cohort will be the final cohort for this Phase 1b study. We anticipate releasing data from the 400 mg cohort in the first half of 2025.

In a transplant setting, when patients are experiencing immunosuppression, they are at high risk of uncontrolled viral replication and severe disease brought on by one or more herpesviruses, including cytomegalovirus (CMV), HSV-1, HSV-2, varicella zoster virus (VZV) and Epstein-Barr virus (EBV). Each of these herpesviruses are highly prevalent, as approximately (1) 60% of transplant patients are CMV-positive; (2) 60% of transplant patients are HSV-positive; (3) 80% of transplant patients are VZV-positive and (4) 45% of transplant patients are EBV-positive. These viruses establish lifelong latent infections and frequently reactivate in transplant patients due to the use of immunosuppressive drugs following transplantation. These uncontrolled viral infections increase the risk of severe disease and serious complications, including organ rejection, graft loss and death, and impacted approximately 95,000 people receiving transplants in 2021 in the United States and Europe.

While there are approved antivirals that are administered in a transplant setting, currently approved antivirals are not active against a broad spectrum of transplant-associated herpesviruses and pose the risk of potentially serious side effects and drug-drug interactions. As a result of these limitations, we identified an opportunity to develop an oral, broad-spectrum NNPI for transplant-associated herpesvirus infections, which could greatly advance treatment.

In December 2024, we nominated 7423 as our development candidate to undergo CTA-enabling studies, which are ongoing.

In addition to our investigational therapy programs that have nominated development candidates and have advanced into clinical studies or CTA-enabling studies, our research team continues to actively focus on proprietary research to discover and develop novel antivirals to treat serious viral diseases.

In October 2023, we entered into an Option, License and Collaboration agreement (the Gilead Collaboration Agreement) with Gilead pursuant to which Gilead (1) exclusively licensed to us its HPI program and its NNPI program, while retaining opt-in rights to these programs and (2) has an option to take an exclusive license, on a program-by-program basis, to all of our other current and future pipeline programs. During the 12-year collaboration term (subject to payment of certain extension fees) and for a specified period thereafter, Gilead may exercise its opt-in rights, on a program-by-program basis, at one of two timepoints—completion of a certain Phase 1 study or completion of a certain Phase 2 study for the first product within the program—upon payment of an opt-in fee ranging from $45.0 million to $125.0 million per program depending on the type of program and when the option is exercised. Pursuant to the Gilead Collaboration Agreement, Gilead made an $84.8 million upfront cash payment to us. In December 2024, we and Gilead entered into the First Amendment to the Gilead Collaboration Agreement, which restructured the timing of specific options exercisable and the fees payable to us under the terms of the Gilead Collaboration Agreement due to an agreed upon development plan for 6250. To facilitate this development plan, (1) we received a payment of $10.0 million from Gilead and (2) the opt-in fee payable by Gilead in connection with 6250 was restructured, though it remains in the range of opt-in fees detailed above. The $10.0 million payment received in connection with the First Amendment to the Gilead Collaboration Agreement is creditable towards future collaboration-related payments payable by Gilead.

If Gilead exercises its opt-in right to any current or future program under the collaboration, we are eligible to receive up to $330.0 million in potential regulatory and commercial milestones on that program, in addition to royalties ranging from the high single-digits to high teens, depending on the clinical stage of the program at the time of the opt-in. Following Gilead’s exercise of its option for each program, we may opt in to cover 40% of the research and development costs in the United States and share 40% of the profits and operating loss in the United States for products within the program in lieu of receiving milestones and royalties for that program in the United States, unless we later opt out of the cost/profit share for the program. Prior to Gilead’s potential exercise of its opt-in, we are primarily responsible for all discovery, research and development on both our programs and the two Gilead-contributed programs. Following Gilead’s opt-in, Gilead will control the further discovery, research, development, and commercialization on any optioned programs. During the term, Gilead will continue to support the collaboration through extension fees of $75.0 million in each of the third, fifth and seventh years of the collaboration.

The Gilead Collaboration Agreement is subject to termination by either party for the other party’s uncured, material breach or insolvency. Subject to certain limitations, we and Gilead both have certain termination for convenience rights, upon sufficient prior written notice, with respect to programs that one party in-licenses from the other (subject to Gilead’s option rights), and with respect to Gilead, for programs it has option rights to (subject to certain time limitations with respect to existing Company programs). Gilead also has a right to terminate the collaborative activities under the Gilead Collaboration Agreement at certain specified points during the collaboration term. Other customary termination rights are further provided in the Gilead Collaboration Agreement.

We and Gilead also entered into a Common Stock Purchase Agreement and an Investor Rights Agreement (together, the Gilead Equity Agreements), which were both amended in June 2024 in connection with a financing transaction, in which a new investor purchased shares of common stock and was issued a warrant (the 2024 Financing Transaction). Pursuant to the Gilead Equity Agreements, Gilead made an upfront equity investment of $15.2 million by purchasing from us 1,089,472 shares of our common stock at a purchase price of $13.92 per share. The terms of the Gilead Equity Agreements provided Gilead the right to elect to purchase additional shares of common stock from us at a premium in an amount that results in Gilead owning 29.9% of our then-outstanding voting common stock. This right was exercised in December 2024, at a purchase price of $21.37 per share, which represents a 35% premium to the 30-trading day volume weighted average price immediately prior to the date of purchase. The Gilead Equity Agreements also include a three-year standstill provision and a two-year lockup provision, each with customary exceptions, and

provide Gilead with certain other stock purchase rights and registration rights, as well as the right to designate two directors (or, alternatively, board observers at Gilead’s election) to our board of directors. In December 2023, Gilead designated Tomas Cihlar, Ph.D. to serve on our board of directors, and in March 2024, Gilead designated Robert D. Cook II to serve on our board of directors.

Gilead participated in the 2024 Financing Transaction on the same terms as the new investor pursuant to the anti-dilution provision in the Investor Rights Agreement. We and Gilead entered into a Securities Purchase Agreement for the issuance and sale, in a private placement, of 179,500 shares of our common stock and a warrant to purchase up to 179,500 shares of our common stock. The warrant sold to Gilead has an exercise price equal to $17.00 per share, became immediately exercisable on the date of issuance and will expire on June 18, 2029. Subject to certain exceptions, neither Gilead nor its affiliates may exercise any portion of the warrant to the extent that Gilead would own more than 19.9% of the number of our shares of common stock outstanding immediately after giving effect to such exercise.

We own a published international Patent Cooperation Treaty (PCT) patent application relating to compositions of matter and methods of using 5366 and derivatives/analogs thereof to treat HSV. Any patents issuing therefrom are expected to expire in 2043. We also own provisional, unpublished and published PCT patent applications relating to synthetic processes, crystal forms and pharmaceutical formulations of 5366. Any patents issuing therefrom are expected to expire in 2043 to 2045.

We have acquired rights to a published PCT patent application relating to compositions of matter and methods of using 1179 and derivatives/analogs thereof to treat HSV. Any patents issuing therefrom are expected to expire in 2043. We also have rights to unpublished PCT patent applications related to crystalline forms and pharmaceutical formulations of 1179. Any patents issuing therefrom are expected to expire in 2044 and 2045, respectively.

We own a published PCT patent application relating to compositions of matter and methods of using compound 6250 and derivatives/analogs thereof to treat HDV and HBV. Any patents issuing therefrom are expected to expire in 2044. We also own a provisional patent application relating to crystalline forms of 6250. Any patents issuing therefrom are expected to expire in 2045.

We own a published PCT patent application which has entered the national phase, relating to compositions of matter and methods of using compound 4334 and derivatives/analogs thereof to treat HBV. Any patents issuing therefrom are expected to expire in 2041. We also own published PCT patent applications, which have entered the national phase, relating to processes for preparing 4334 and crystalline forms of 4334. Any patents issuing therefrom are expected to expire in 2042.

Finally, we own a provisional patent application relating to compositions of matter and methods of using broad-spectrum NNPIs to treat various herpes viruses.

Government authorities in the United States, at the federal, state and local level, and in other countries extensively regulate, among other things, the research, development, testing, manufacture, including any manufacturing changes, packaging, storage, recordkeeping, labeling, advertising, promotion, distribution, marketing, post-approval monitoring and reporting, import and export of pharmaceutical products, such as those we are developing.

In the United States, the FDA regulates drugs under the Federal Food, Drug, and Cosmetic Act (FDCA) and implementing regulations. The process of obtaining regulatory approvals and subsequent compliance with appropriate federal, state, local and foreign statutes and regulations requires the expenditure of substantial time and financial resources. Failure to comply with the applicable U.S. requirements at any time during the product development process, approval process or after approval may subject an applicant or sponsor to a variety of administrative or judicial sanctions, such as the FDA’s refusal to approve pending applications, withdrawal of an approval, license revocation, imposition of a clinical hold, issuance of warning letters and untitled letters, product recalls, product seizures, total or

partial suspension of production or distribution, injunctions, fines, refusals of government contracts, restitution, disgorgement of profits or civil or criminal penalties.

The process required by the FDA before a drug may be marketed in the United States generally involves the following:

Nonclinical studies include laboratory evaluation of product chemistry and formulation, as well as in vitro and animal studies to assess the potential for AEs and in some cases to establish a rationale for therapeutic use. The conduct of nonclinical studies is subject to federal regulations and requirements, including GLP regulations for safety/toxicology studies. An IND sponsor must submit the results of the nonclinical tests, together with manufacturing information, analytical data, any available clinical data or literature and plans for clinical studies, among other things, to the FDA as part of an IND. Some long-term nonclinical testing, such as animal tests of reproductive AEs and carcinogenicity, may continue after the IND is submitted. For some products, the FDA may waive the need for certain nonclinical tests. An IND automatically becomes effective 30 days after receipt by the FDA, unless before that time the FDA raises concerns or questions related to one or more proposed clinical studies and places the trial on clinical hold. If an IND or clinical study is placed on clinical hold, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical study can begin. As a result, submission of an IND may not result in the FDA allowing clinical studies to commence.

Clinical studies involve the administration of the investigational new drug to human subjects under the supervision of qualified investigators in accordance with GCP requirements, which include, among other things, the requirement that all research subjects provide their informed consent in writing before their participation in any clinical study. Clinical studies are conducted under written study protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety, and the effectiveness criteria to be evaluated. A protocol for each clinical study and any subsequent protocol amendments must be submitted to the FDA as part of the IND. In addition, an IRB at each institution participating in the clinical study must review and approve the plan for any clinical study before it

commences at that institution, and the IRB must conduct continuing review. The IRB must review and approve, among other things, the study protocol and informed consent information to be provided to study subjects. An IRB must operate in compliance with FDA regulations. Additionally, some clinical trials are overseen by an independent group of qualified experts organized by the clinical trial sponsor, known as a data safety monitoring board or committee. This group provides authorization for whether a trial may move forward at designated checkpoints based on access to certain data from the trial. Information about certain clinical studies must be submitted within specific timeframes to the National Institutes of Health for public dissemination at www.clinicaltrials.gov. The Food and Drug Omnibus Reform Act (FDORA), which was signed into law on December 29, 2022, made numerous amendments to the FDCA including provisions intended to, among other things, decentralize and modernize clinical trials and enhance diversity in clinical trial populations.

Human clinical studies are typically conducted in three sequential phases, which may overlap or be combined:

Progress reports detailing the results of the clinical studies must be submitted at least annually to the FDA. Additionally, IND safety reports must be submitted to the FDA and the investigators within 15 calendar days after determining that the information qualifies for reporting. IND safety reports are required for serious and unexpected adverse reactions, findings from animal or in vitro testing or other studies that suggest a significant risk to humans, and any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure. In addition, a sponsor must notify the FDA within seven calendar days after receiving information concerning any unexpected fatal or life-threatening suspected adverse reaction. Phase 1, Phase 2 and Phase 3 clinical studies may not be completed successfully within any specified period, or at all. Furthermore, the FDA or the sponsor may suspend or terminate a clinical study at any time on various grounds, including a finding that the research subjects are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical study at its institution if the clinical study is not being conducted in accordance with the IRB’s requirements or if the drug has been associated with unexpected serious harm to patients.

A manufacturer of an investigational drug for a serious disease or condition is required to make available, such as by posting on its website, its policy regarding evaluating and responding to requests for individual patient access to such investigational drug. This requirement applies on the earlier of the first initiation of a Phase 2 or Phase 3 trial of the investigational drug or, as applicable, 15 days after the drug receives a designation as a breakthrough therapy, Fast Track product, or regenerative advanced therapy. There also are requirements governing the reporting of ongoing clinical trials and completed clinical trial results to public registries.

After the completion of required clinical testing, the results of the nonclinical studies and clinical studies, together with detailed information relating to the product’s chemistry, manufacture, controls and proposed labeling, among other things, are submitted to the FDA as part of an NDA requesting approval to market the product for one or more indications. Under federal law, the submission of most NDAs is additionally subject to a substantial application user fee, currently $4.0 million, and the sponsor of an approved NDA is also subject to an annual program fee currently set at $0.42 million through September 30, 2024. These fees are typically adjusted on October 1 each year.

The FDA conducts a preliminary review of all NDAs within the first 60 days after submission before accepting them for filing to determine whether they are sufficiently complete to permit substantive review. The FDA may request additional information rather than accept an NDA for filing. In this event, the application must be resubmitted with the additional information. The resubmitted application is also subject to review before the FDA accepts it for filing. Once the submission is accepted for filing, the FDA begins an in-depth substantive review. The FDA has agreed to specified performance goals in the review of NDAs. Under these goals, the FDA has committed to review most original applications for non-priority products within ten months, and most original applications for priority review products, that is, drugs for a serious or life-threatening condition that the FDA determines represent a significant improvement over existing therapy, within six months. For NDAs for novel products, the ten- and six-month time periods runs from the filing date; for all other original applications, the ten- and six-month time periods run from the submission date. The review process may be extended by the FDA for three additional months to consider certain information or clarification regarding information already provided in the submission. Despite these review goals, it is not uncommon for FDA review of an NDA to extend beyond the goal date. The FDA may also refer applications for novel drugs or products that present difficult questions of safety or efficacy to an advisory committee, typically a panel that includes clinicians and other experts, for review, evaluation and a recommendation as to whether the application should be approved. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions.

Before approving an NDA, the FDA typically will inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. In addition, before approving an NDA, the FDA will typically inspect one or more clinical sites to assure compliance with GCP and integrity of the clinical data submitted. With passage of the FDORA, Congress clarified the FDA’s authority to conduct inspections by expressly permitting inspection of facilities involved in the preparation, conduct, or analysis of clinical and nonclinical studies submitted to FDA as well as other persons holding study records or involved in the study process.

After the FDA’s evaluation of the NDA and inspection of the manufacturing facilities, the FDA may issue an approval letter or a complete response letter. An approval letter authorizes commercial marketing of the drug with specific prescribing information for specific indications. A complete response letter indicates that the NDA will not be approved in its present form and generally outlines the deficiencies in the submission, which may require substantial additional testing or information in order for the FDA to reconsider the application. If and when those deficiencies have been addressed to the FDA’s satisfaction in a resubmission of the NDA, the FDA will issue an approval letter. The FDA has committed to reviewing such resubmissions in two or six months depending on the type of information included. Even with submission of this additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval and refuse to approve the NDA. Even if the FDA approves a product, it may limit the approved indications for use for the product, require that contraindications, warnings or precautions be included in the product labeling, require that post-approval studies, including Phase 4 clinical studies, be conducted to further assess a drug’s safety after approval, require testing and surveillance programs to monitor the product after commercialization, or impose other conditions, including distribution and use restrictions or other risk management mechanisms, including REMS, which can materially affect the potential market and profitability of the product or impose new labeling, testing or distribution and use requirements. The FDA may prevent or limit further marketing of a product based on the results of post-market studies or surveillance programs. After approval, some types of changes to the approved product, such as adding new indications, manufacturing changes and additional labeling claims, are subject to further testing requirements and FDA review and approval.

The FDA is required to facilitate and expedite the development and review of drugs that are intended for the treatment of a serious or life-threatening disease or condition for which there is no effective treatment and which demonstrate the potential to address unmet medical needs for the disease or condition. Under the Fast Track program, the sponsor of a new product candidate may request the FDA to designate the product for a specific indication as a Fast Track product concurrent with or after the filing of the IND for the product candidate. The FDA must determine if the product candidate qualifies for fast track designation within 60 calendar days after receipt of the sponsor’s request.

In addition to other benefits, such as the ability to have greater interactions with the FDA, the FDA may initiate review of sections of a Fast Track product’s NDA before the application is complete. This rolling review is available if the applicant provides and the FDA approves a schedule for the submission of the remaining information and the applicant pays applicable user fees. However, the FDA’s time period goal for reviewing a Fast Track application does not begin until the last section of the NDA is submitted. In addition, the Fast Track designation may be withdrawn by the FDA if the FDA believes that the designation is no longer supported by data emerging in the clinical study process.

Under FDA policies, a product candidate may be eligible for priority review, a review generally completed within a six-month time frame from the date a complete application is filed. Products generally are eligible for priority review if they are intended for treatment of a serious or life-threatening disease or condition and provide a significant improvement in safety or effectiveness compared to marketed products in the treatment, diagnosis or prevention of a serious disease or condition.

Under the FDA’s accelerated approval regulations, the FDA may approve a drug for a serious or life-threatening illness that provides meaningful therapeutic benefit to patients over existing treatments based upon a surrogate endpoint that is reasonably likely to predict clinical benefit or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality (IMM). In clinical studies, a surrogate endpoint is a measurement of laboratory or clinical signs of a disease or condition that substitutes for a direct measurement of how a participant feels, functions or survives. Surrogate endpoints can often be measured more easily or more rapidly than clinical endpoints. A product candidate approved on this basis is subject to rigorous post-marketing compliance requirements, including the completion of Phase 4 or post-approval clinical studies to confirm the effect on the clinical endpoint. Failure to conduct required post-approval studies, or confirm a clinical benefit during post-marketing studies, would allow the FDA to withdraw the drug from the market on an expedited basis. All promotional materials for drug candidates approved under accelerated regulations are subject to prior review by the FDA. With the passage of the FDORA, the FDA is authorized to require a post-approval study to be underway prior to approval or within a specified time period following approval. FDORA also requires the FDA to specify conditions of any required post-approval study and requires sponsors to submit progress reports for required post-approval studies and any conditions required by the FDA until completion or termination of the study. FDORA further enables the FDA to initiate criminal prosecutions for the failure to conduct with due diligence a required post-approval study, including a failure to meet any required conditions specified by the FDA or to submit timely reports.

A sponsor can request designation of a product candidate as a “breakthrough therapy.” A breakthrough therapy is defined as a drug that is intended, alone or in combination with one or more other drugs, to treat a serious or life-threatening disease or condition, and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. Drugs designated as breakthrough therapies also may be eligible for priority review. The FDA must take certain actions, such as holding timely meetings and providing advice, intended to expedite the development and review of an application for approval of a breakthrough therapy. Even if a product qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened.

Under the Orphan Drug Act, as amended, the FDA may grant orphan drug designation to drugs intended to treat a rare disease or condition, which is generally defined as a disease or condition that affects fewer than 200,000 individuals in the United States or that affects more than 200,000 individuals in the United States and for which there is no reasonable expectation that the cost of developing and making available the drug for the disease or condition will be recovered from sales of the product in the United States. Orphan drug designation must be requested before submitting an NDA. After the FDA grants orphan drug designation, the identity of the product and its potential orphan use are disclosed publicly by the FDA. Orphan drug designation does not shorten the duration of the regulatory review and approval process. If a product that has orphan designation subsequently receives the first FDA approval for a particular

active ingredient for the disease or condition for which it has such designation, the product is entitled to Orphan Drug exclusivity, which means that the FDA may not approve other applications to market the same product for the same indication for seven years, except in limited circumstances, such as a showing of clinical superiority to the product with orphan drug exclusivity. A drug will be considered clinically superior if it is shown to be safer, more effective or makes a major contribution to patient care. Orphan drug exclusivity does not prevent the FDA from approving a different drug for the same orphan disease or condition, or the same drug for a different disease or condition. Among the other benefits of orphan drug designation are tax credits for certain research and a waiver of the NDA application user fee.

Under the Pediatric Research Equity Act of 2003, as amended, an NDA or supplement to an NDA for drug with certain novel features (e.g., new active ingredient, new indication) must contain data that are adequate to assess the safety and effectiveness of the drug for the claimed indications in all relevant pediatric subpopulations, and to support dosing and administration for each pediatric subpopulation for which the product is safe and effective. The FDA may, on its own initiative or at the request of the applicant, grant deferrals for submission of some or all pediatric data until after approval of the product for use in adults, or full or partial waivers from the pediatric data requirements. A sponsor of a new drug subject to the above pediatric testing requirements also is required to submit to the FDA a pediatric study plan generally 60 days after an end-of-Phase 2 meeting with the agency. Generally, the pediatric data requirements do not apply to products with orphan drug designation.

Any drug manufactured or distributed by us pursuant to FDA approvals will be subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to recordkeeping, periodic reporting, product sampling and distribution, advertising and promotion and reporting of adverse experiences with the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval.

The FDA may impose a number of post-approval requirements, including REMS, as a condition of approval of an NDA. For example, the FDA may require post-marketing testing, including Phase 4 clinical studies, and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization.

In addition, drug manufacturers and other entities involved in the manufacture and distribution of approved drugs are required to register their establishments with the FDA and state agencies and are subject to periodic unannounced inspections by the FDA and these state agencies for compliance with cGMP requirements. Changes to the manufacturing process are strictly regulated and often require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting and documentation requirements upon us and any third-party manufacturers that we may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the areas of production and quality control to maintain cGMP compliance.

Once an approval is granted, the FDA may withdraw the approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including AEs of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information, imposition of post-market studies or clinical studies to assess new safety risks or imposition of distribution or other restrictions under a REM program. Other potential consequences include, among other things:

The FDA strictly regulates marketing, labeling, advertising and promotion of products that are placed on the market. Drugs generally may be promoted only for the approved indications and in accordance with the provisions of the approved labeling. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off label uses, and a company that is found to have improperly promoted off label uses may be subject to significant liability.

As part of the sales and marketing process, pharmaceutical companies frequently provide samples of approved drugs to physicians. The Prescription Drug Marketing Act (PDMA) regulates the distribution of drug samples at the federal level and sets minimum standards for the registration and regulation of drug distributors by the states. Both the PDMA and state laws limit the distribution of prescription pharmaceutical product samples and impose requirements to ensure accountability in distribution. In addition, the PDMA sets forth civil and criminal penalties for violations.

In order to market any product outside of the United States, we would need to comply with numerous and varying regulatory requirements of other countries regarding safety and efficacy and governing, among other things, clinical studies, marketing authorization, commercial sales and distribution of our products. Whether or not we obtain FDA approval for a product, we would need to obtain the necessary approvals by the comparable regulatory authorities of foreign countries before we can commence clinical studies or marketing of the product in those countries. The approval process varies from country to country and can involve additional product testing and additional administrative review periods. The time required to obtain approval in other countries might differ from and be longer than that required to obtain FDA approval. Regulatory approval in one country does not ensure regulatory approval in another, but a failure or delay in obtaining regulatory approval in one country may negatively impact the regulatory process in others.

Significant uncertainty exists as to the coverage and reimbursement status of any drug products for which we may obtain regulatory approval. Sales of any of our product candidates, if approved, will depend, in part, on the extent to which the costs of the products will be covered by third-party payors, including government health programs such as Medicare and Medicaid, commercial health insurers and managed care organizations. The process for determining whether a payor will provide coverage for a drug product may be separate from the process for setting the price or reimbursement rate that the payor will pay for the drug product once coverage is approved. Third-party payors may limit coverage to specific drug products on an approved list, or formulary, which might not include all of the approved drugs for a particular indication.

The containment of healthcare costs has become a priority of federal, state and foreign governments, and the prices of drugs have been a focus in this effort. Third-party payors are increasingly challenging the prices charged for medical products and services and examining the medical necessity and cost-effectiveness of medical products and services, in addition to their safety and efficacy. Accordingly, we may need to conduct expensive pharmacoeconomic studies in order to demonstrate the medical necessity and cost-effectiveness of our product candidates, in addition to the trials required to obtain FDA or other comparable regulatory approvals. If these third-party payors do not consider our products to be cost-effective compared to other available therapies, they may not cover our products after approval as a benefit under their plans or, if they do, the level of payment may not be sufficient to enable us to maintain price levels high enough to realize an appropriate return on our investment in product development. Further, one payor’s determination to provide coverage for a product, if approved, does not assure that other payors will also provide coverage and reimbursement for the product, and the level of coverage and reimbursement can differ significantly from payor to payor.

Pricing and reimbursement schemes vary widely from country to country. Some countries provide that drug products may be marketed only after a reimbursement price has been agreed. Some countries may require the completion of additional studies that compare the cost-effectiveness of a particular product candidate to currently available therapies. For example, the European Union (EU) provides options for its member states to restrict the range of drug products for which their national health insurance systems provide reimbursement and to control the prices of medicinal products for human use. EU member states may approve a specific price for a drug product or may instead adopt a

system of direct or indirect controls on the profitability of us placing the drug product on the market. Other member states allow companies to fix their own prices for drug products but monitor and control company profits. The downward pressure on health care costs in general, particularly prescription drugs, has become very intense. As a result, increasingly high barriers are being erected to the entry of new products. In addition, in some countries, cross-border imports from low-priced markets exert competitive pressure that may reduce pricing within a country. There can be no assurance that any country that has price controls or reimbursement limitations for drug products will allow favorable reimbursement and pricing arrangements for any of our products.

The marketability of any products for which we may receive regulatory approval for commercial sale is dependent on the availability of adequate coverage and reimbursement from government and third-party payors. In addition, the emphasis on managed care in the United States has increased and we expect will continue to increase the pressure on drug pricing. Coverage policies, third-party reimbursement rates and drug pricing regulation may change at any time. For example the Affordable Care Act of 2010, as amended by, the Health Care and Education Reconciliation Act (collectively, ACA), among other things, imposed an annual fee on any entity that manufactures or imports certain branded prescription drugs, increased the minimum Medicaid rebates owed by most manufacturers under the Medicaid Drug Rebate Program, and established the Medicare Part D coverage gap discount program. In addition to these provisions, the ACA established a number of bodies whose work may have a future impact on the market for certain pharmaceutical products, including the Patient-Centered Outcomes Research Institute, established to oversee, identify priorities in, and conduct comparative clinical effectiveness research, and the Center for Medicare and Medicaid Innovation within the Centers for Medicare and Medicaid Services, established to test innovative payment and service delivery models to lower Medicare and Medicaid spending.

Since its enactment, there have been executive, judicial, and Congressional challenges to certain aspects of the ACA. For example, during his first administration, President Trump issued directives designed to delay the implementation of certain ACA provisions or otherwise circumvent requirements for health insurance mandated by the ACA, and Congress has considered legislation that would repeal, or repeal and replace all or part of the ACA. While Congress has not passed comprehensive repeal legislation, several bills affecting the implementation of certain taxes under the ACA have been signed into law. In addition, the Tax Cuts and Jobs Act, effectively repealed the individual health insurance mandate, which is considered a key component of the ACA. On June 17, 2021, the U.S. Supreme Court dismissed a challenge on procedural grounds that argued the ACA is unconstitutional in its entirety because the “individual mandate” was repealed by Congress. In January 2025, the U.S. Supreme Court granted certiorari to review a lower court's decision that the ACA's requirement that group health plans and health insurance issuers cover certain preventative services without cost-sharing is unconstitutional.

In addition, other legislative changes have been proposed and adopted since the ACA was enacted. These changes included aggregate reductions to Medicare payments to providers of up to 2% per fiscal year, which will remain in effect through 2032, unless Congress takes additional action. Further, in January 2013, then President Obama signed into law the American Taxpayer Relief Act of 2012, which, among other things, reduced Medicare payments to several providers, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years. These and other laws may result in additional reductions in Medicare and other healthcare funding and otherwise affect the prices we may obtain for any of our product candidates for which we may obtain regulatory approval or the frequency with which any such product candidate is prescribed or used.

Additionally, there has been increasing legislative and enforcement interest in the United States with respect to drug pricing practices. Specifically, there have been several recent United States Congressional inquiries and proposed and enacted federal legislation designed to, among other things, bring more transparency to drug pricing, reduce the cost of prescription drugs under Medicare, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for drugs. For example, the Inflation Reduction Act of 2022 (IRA) enacted on August 16, 2022, seeks to reduce prescription drug costs by, among other provisions, allowing Medicare to negotiate prices for certain high-cost prescription drugs in Medicare Parts B and D, imposing an excise tax on pharmaceutical manufacturers that refuse to negotiate pricing with Medicare, and requiring inflation rebates to limit annual drug price increases in Medicare. These provisions began taking effect progressively starting in 2023, and, in January 2025, CMS announced the 15 drugs selected for the second cycle of Medicare drug price negotiations. Beginning in 2025, the IRA also eliminates the coverage gap under Medicare Part D by significantly lowering the enrollee maximum out-of-pocket cost and imposing on new manufacturer discount program. However, various industry stakeholders, including certain pharmaceutical companies and industry trade organizations have

initiated lawsuits against the federal government asserting that the price negotiation provisions of the IRA are unconstitutional. The impact of these judicial challenges and future government reform measures on us and the pharmaceutical industry as a whole is unclear. Further, on December 7, 2023, the Biden administration announced an initiative to control the price of prescription drugs through the use of march-in rights under the Bayh-Dole Act. On December 8, 2023, the National Institute of Standards and Technology published for comment a Draft Interagency Guidance Framework for Considering the Exercise of March-In Rights which for the first time includes the price of a product as one factor an agency can use when deciding to exercise march-in rights.

In addition, in September 2020, the FDA issued a final rule that sets up a legal framework for allowing the importation of certain prescription drugs from Canada, and the CMS issued guidance that addresses the treatment of certain imported drugs under the Medicaid Drug Rebate Program. On January 5, 2024, the FDA authorized the state of Florida’s Section 804 Importation Program, which is the first major step in allowing the state to import certain prescription drugs from Canada. If the program is ultimately approved, it will be the first such program authorized in the United States.

Although a number of these and other proposed measures may require authorization through additional legislation to become effective, and the current Trump administration may reverse or otherwise change measures implemented by the prior administration, both the Trump administration and Congress have indicated that they will continue to take action to control drug costs.

At the state level, individual states are increasingly aggressive in passing legislation and implementing regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures. These measures could reduce the ultimate demand for our products, if approved, or put pressure on our product pricing. We expect that additional state and federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for healthcare products and services, which could result in reduced demand for our product candidates or additional pricing pressures.

In the United States, our activities are potentially subject to regulation by various federal, state and local authorities in addition to the FDA, including but not limited to, CMS, other divisions of the U.S. Department of Health and Human Services (e.g., the Office of Inspector General), the U.S. Department of Justice (DOJ), and individual U.S. Attorney offices within the DOJ, and state and local governments. For example, the Company’s business practices, including its research and sales, marketing and scientific/ educational grant programs may be required to comply with federal and state fraud and abuse laws, false claims laws, the data privacy, security provisions and breach notification provisions of the Health Insurance Portability and Accountability Act (HIPAA), federal transparency requirements and similar state laws, each as amended. The laws that may affect our ability to operate include, but are not limited to:

Additionally, we are subject to state and non-U.S. equivalents of each of the healthcare laws described above, among others, some of which may be broader in scope and may apply regardless of the payor. For example, many U.S. states have adopted laws similar to the federal Anti-Kickback Statute, some of which apply to the referral of patients for healthcare services reimbursed by any source, not just governmental payors, including private insurers. In addition, some states require pharmaceutical companies to implement compliance programs, comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government, or to track and report gifts, compensation and other remuneration provided to physicians and other healthcare providers. There also are state laws that require the reporting of marketing expenditures or drug pricing, including information pertaining to and justifying price increases, state and local laws that require the registration of pharmaceutical sales representatives or other state or local licensure, state laws that prohibit various marketing-related activities, such as the provision of certain kinds of gifts or meals, and state laws that require the posting of information relating to clinical trials and their outcomes. There are ambiguities as to what is required to comply with these state requirements and if we fail to comply with an applicable state law requirement, we could be subject to penalties.

In addition, regulators globally are also imposing greater monetary fines for privacy violations. In respect of our engagement of European contract research organizations (CROs) in the context of clinical trials, the General Data Protection Regulation (EU GDPR), which went into effect on May 25, 2018, applies. The EU GDPR applies to any

company established in the EU as well as to those outside the EU if they collect and use personal data in connection with the offering goods or services to individuals in the EU or the monitoring of their behavior. The EU GDPR enhances data protection obligations for processors and controllers of personal data, including, for example, expanded disclosures about how personal information is to be used, limitations on retention of information, mandatory data breach notification requirements and onerous new obligations on services providers. Noncompliance with the EU GDPR may result in monetary penalties of up to €20 million or 4% of worldwide revenue, whichever is higher. In addition, violations of the EU GDPR could result in regulatory investigations, reputational damage, orders to cease and/or change our processing activities, enforcement notices and/or assessment notices (for compulsory audit). We may also face civil claims, including representative actions and other class action type litigation (where individuals have suffered harm), potentially amounting to significant compensation or damages liabilities as well as associated costs, diversion of internal resources and reputational harm. This is as the EU GDPR confers a private right of action on data subjects and consumer associations to lodge complaints with supervisory authorities, seek judicial remedies, and obtain compensation for damages resulting from violations.

The EU GDPR may increase our responsibility and liability in relation to personal data that we process where such processing is subject to the EU GDPR, and we may be required to put in place additional mechanisms to ensure compliance with the EU GDPR, including as implemented by individual countries. The EU GDPR (covering the EEA) imposes strict rules on the transfer of personal data out of the EU to a "third country," including the United States. In July 2020, the EU-US Privacy Shield was invalidated as a valid personal data transfer mechanism and on June 27, 2021, the European Commission published a new set of modular standard contractual clauses (New SCCs). The New SCCs must be used for all relevant transfers of personal data outside the European Economic Area (EEA) (since December 27, 2022). On July 11, 2023, the European Commission entered into force its adequacy decision for the EU-US Data Privacy Framework (a new framework for transferring personal information from the EEA to the United States), having determined that such framework ensures that the protection of personal information transferred from the EEA to the US will be comparable to the protection offered in the EU. However, this decision is subject to legal challenges and ultimately may be invalidated by the Court of Justice of the European Union (CJEU) just as the EU-US Privacy Shield was. We currently rely on the New SCCs for both intragroup and third-party data transfers from the EEA, however the cross-border data transfer landscape in the EEA is continually developing, and we are monitoring these developments. We may, in addition to other impacts, experience additional costs associated with increased compliance burdens and be required to engage in new contract negotiations with third parties that aid in processing data on our behalf or localize certain data.

California enacted the California Consumer Privacy Act (CCPA), which creates new individual privacy rights for California consumers (as defined in the law) and places increased privacy and security obligations on entities handling personal data of consumers or households. The CCPA will require covered companies to provide certain disclosures to consumers about its data collection, use and sharing practices, and to provide affected California residents with ways to opt-out of certain sales or transfers of personal information. While there is currently an exception for protected health information that is subject to HIPAA and clinical trial regulations, as currently written, the CCPA may impact our business activities. Additionally, the California Privacy Rights Act (CPRA), which went into effect on January 1, 2023, imposes additional obligations on companies covered by the legislation and expands consumers’ rights with respect to certain sensitive personal information, among other things. The CPRA also creates a new state agency that will be vested with authority to implement and enforce the CCPA and the CPRA. Other states, including Virginia and Colorado have similarly passed data privacy laws that will regulate how businesses collect and share personal information.

From time to time, legislation is drafted, introduced and passed in Congress that could significantly change the statutory provisions governing the testing, approval, manufacturing, marketing, and reimbursement status of products regulated by the FDA. In addition to new legislation, FDA regulations and policies are often revised or interpreted by the agency in ways that may significantly affect our business and our products. It is impossible to predict whether further legislative changes will be enacted or whether FDA regulations, guidance, policies or interpretations will be changed or what the effect of such changes, if any, may be.

We are conscious of the extensive and evolving regulatory frameworks in the jurisdictions in which we operate. There are changes in the regulatory landscape relating to new and emerging technologies such as artificial intelligence (AI), which we use in a limited capacity solely to assist our employees in selecting chemical compounds to evaluate. The

EU has developed a standalone law to govern the offering and use of AI systems in the EU (AI Act), which entered into force on August 1, 2024. The AI Act imposes regulatory requirements onto AI system providers, importers, distributors, and deployers, in accordance with the level of risk involved with the AI system (“unacceptable,” “high,” “limited,” and “minimal” risk). General-purpose AI systems have also been made subject to a number of requirements under the AI Act—mostly akin to the requirements that apply to high-risk AI systems. The AI Act will become enforceable in a gradual manner—depending on the regulatory requirement in question, and ranging anywhere from six to 36 months following adoption and entry into force of the AI Act. Non-compliance with the AI Act may be subject to regulatory fines of up to 7% of annual worldwide turnover or €35 million. We are actively assessing the scope of application, impact, and risk of these developments in the EU and the UK on our business and will continue to assess this moving forward. The proposed European Health Data Space (EHDS) Regulation introduces stricter requirements for the collection, processing, and sharing of electronic health data across the EU. If enacted, EHDS may significantly impact our ability to conduct clinical trials, particularly those relying on real-world data, patient registries, or cross-border research collaborations. Additionally, the EU Data Act introduces new obligations regarding the access, sharing, and use of data generated by connected devices, digital platforms, and business-to-business and business-to-government data exchanges. As we conduct clinical trials and utilize digital health technologies and real-world data for research and development, compliance with the EU Data Act may introduce significant regulatory and operational challenges. Non-compliance with any of these regulations may result in fines, operational disruptions or reputational harm, and could impact our financial performance. We are actively assessing the scope of application, impact, and risk of these developments in the EU on our business and will continue to assess this moving forward.

The pharmaceutical and biotechnology industry is very competitive, and the development and commercialization of new drugs is influenced by rapid technological developments and innovation. We face competition from several companies developing and commercializing products that will be competitive with our drug candidates, including large pharmaceutical and smaller biotechnology companies. Additionally, new entrants may potentially enter the market. Potential competitors include GlaxoSmithKline plc, Enanta Pharmaceuticals, Inc., Arbutus Biopharma Corporation, Vir Bio, Bluejay Therapeutics, Huahui Health, Aligos Therapeutics and AiCuris Anti-infective Cures AG, among others. Additionally, we may face competition from currently available HBV treatments. Some of the competitive development programs from these companies may be based on scientific approaches that are similar to our approach, and others may be based on entirely different approaches. Potential competitors also include academic institutions, government agencies and other public and private research organizations that conduct research, seek patent protection and establish collaborative arrangements for research, development, manufacturing and commercialization of products similar to ours or that otherwise target indications that we are pursuing.

We currently rely on third-party manufacturers to supply the quantities of our investigational product candidates used in our clinical and nonclinical studies. We currently have no plans to establish any manufacturing facilities for our product candidates.

As of December 31, 2024, we had 73 total employees and contracts with a number of temporary contractors, consultants and CROs. The majority of our employees work out of our facility in South San Francisco, California. We also have a small number of remote employees spread across the United States and one remote employee in the UK.

We continually evaluate our needs and make strategic choices regarding whether to hire internal teams or outsource certain functions to CROs or contract manufacturing organizations (CMOs), as appropriate. We currently outsource our clinical study management to various CROs and utilize certain CMOs to manufacture both the drug substance and the drug product used in our ongoing and planned clinical studies.

We compete with both large and small companies in our industry for a limited number of qualified applicants to fill highly specialized needs. We generally target our base salaries and annual performance-based cash bonuses at the 50th percentile of our peers and our long-term equity incentive compensation, which all employees receive, between the 50th and 75th percentiles of our peers. In certain circumstances, we offer compensation above these levels, based on a candidate’s experience, criticality, amount of responsibility and either individual or Company-wide performance. We routinely review our employees’ base salaries to ensure they remain market competitive. Both annual

performance-based cash bonuses and long-term equity compensation increase as a percentage of total compensation based on employees’ levels of responsibility. We also offer comprehensive benefits packages to all of our employees, including: 100% Company-covered medical, dental and vision coverage for employees and their families; a 401k program with a Company match; a comprehensive employee assistance program, an employee stock purchase plan; and paid family leave. Our benefits packages also include paid time-off benefits, flexible spending plans, commuter benefits and life and long-term care benefits.

A large majority of our employees have advanced degrees, and we also offer an educational assistance program that reimburses employees up to a maximum amount per year for courses that directly enhance his or her area of professional work or contribute to his or her immediate career growth. This program demonstrates our commitment to analytical growth, enhanced knowledge and professional development.

On September 27, 2023, we received a letter from the Listing Qualifications Department of the Nasdaq Stock Market notifying us that, because the bid price for our common stock had closed below $1.00 per share for the prior 30 consecutive business days, we were not in compliance with Nasdaq Listing Rule 5450(a)(1), which is the minimum bid price requirement for continued listing on the Nasdaq Global Select Market. In accordance with Nasdaq Listing Rule 5810(c)(3)(A), we were provided a 180-calendar day period, or until March 25, 2024, to regain compliance with the minimum bid price requirement. To regain compliance with the Nasdaq Listing Rules, on January 31, 2024, our stockholders approved a reverse stock split of our common stock at a range of ratios between 1-for-7 to 1-for-17, and our board of directors approved the implementation of a reverse stock split at a ratio of 1-for-12 shares of our common stock (the Reverse Stock Split). The Reverse Stock Split was effective as of February 9, 2024, our common stock began trading on the Nasdaq Global Select Market on an as-split basis on February 12, 2024, and the Company regained compliance with the minimum bid price requirement of the Nasdaq Listing Rules on February 27, 2024, by having the closing bid price of our common stock exceed $1.00 for a minimum of ten consecutive trading days during the compliance period.

All share and per share amounts of our common stock presented in this Annual Report on Form 10-K have been adjusted to reflect the 1-for-12 Reverse Stock Split.

We were incorporated in Delaware in October 2005 under the name South Island Biosciences, Inc. (which was changed to Ventrus Biosciences, Inc. in April 2007). On July 11, 2014, we acquired Assembly Pharmaceuticals, Inc., a private company, through a merger with our wholly owned subsidiary (the Merger). In connection with the Merger, we changed our name from Ventrus Biosciences, Inc. to Assembly Biosciences, Inc.

Our principal executive office is at Two Tower Place, 7th Floor, South San Francisco, California 94080. Our telephone number is (833) 509-4583.

Our website address is www.assemblybio.com. We routinely post, or have posted, important information for investors on our website in the “Investors” section. We use this website as a means of disclosing material information in compliance with our disclosure obligations under Regulation FD. Accordingly, investors should monitor the “Investors” section of our website, in addition to following our press releases, Securities and Exchange Commission (SEC) filings, presentations and webcasts. We make available free of charge through our website our press releases, Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and all amendments to those reports as soon as reasonably practicable after electronically filed with or furnished to the SEC.

The information contained on our website is not a part of, and should not be construed as being incorporated by reference, into this report.

The reports filed with the SEC by us and by our officers, directors and significant stockholders are available for review on the SEC’s website at www.sec.gov.

You should carefully consider the following risk factors, together with all other information in this report, including our consolidated financial statements and notes thereto, and in our other filings with the SEC. If any of the following risks, or other risks not presently known to us or that we currently believe to not be material, develop into actual events, then our business, financial condition, results of operations or prospects could be materially adversely affected. If that happens, the market price of our common stock could decline, and stockholders may lose all or part of their investment.

We have no approved products and depend on the future success of the product candidates in our research and development pipeline. We cannot be certain that we or our collaborators will be able to obtain regulatory approval for, or successfully commercialize, product candidates from our current pipeline or any other product candidates that we may subsequently identify, license or otherwise acquire.

We and our collaborators are not permitted to market or promote any products in the United States, Europe, China or other countries before we receive regulatory approval from the FDA or comparable foreign regulatory authorities, and we may never receive such regulatory approval for our current product candidates. We have not submitted a new drug application (NDA) to the FDA or comparable applications to other regulatory authorities and do not expect to be in a position to do so in the near future.

All our product candidates are in clinical development or in varying stages of nonclinical development. Data supporting our clinical development programs are derived from nonclinical data that support our early stage clinical programs, which will determine whether pivotal studies are appropriate. These pivotal studies are necessary to support regulatory approval, and it may be years before these larger, pivotal studies are completed, if ever.

In addition to our current product pipeline, we may identify, license or otherwise acquire rights to other technologies or product candidates. Any such transactions would involve numerous risks, and we may be unsuccessful in entering into any such transactions or developing any such technologies or product candidates.

For these reasons, our drug discovery and development may not be successful, and we may be unable to continue clinical development of our product candidates and may not generate product approvals or product revenue, any of which could have a material adverse impact on our business, results of operations and financial condition.

We are not currently profitable and might never become profitable, and we will need additional financing to complete the development of any product candidates and fund our activities into the future.

We do not have any approved products, and we have a history of losses. We expect to continue to incur substantial operating and capital expenditures to advance our current product candidates through clinical development, continue research and discovery efforts to identify potential additional product candidates and seek regulatory approvals for our current and future product candidates. All operations and capital expenditures will be funded from cash on hand, securities offerings, debt financings and payments we may receive from out-licenses, collaborations or other strategic arrangements. Adverse geopolitical and macroeconomic developments, such as ongoing military conflicts, related sanctions, actual and anticipated changes in interest rates, economic inflation and the responses by central banking authorities to control such inflation, could affect our ability to access capital as and when needed.

There is no assurance that we will be successful in raising any necessary additional capital on terms that are acceptable to us, or at all. If we are unable to develop and commercialize any product candidates and generate sufficient revenue or raise capital, we could be forced to reduce staff, delay, scale back or discontinue product development and clinical studies, sacrifice attractive business opportunities, cease operations entirely and sell, or otherwise transfer, all or substantially all of our remaining assets, which would likely have a material adverse impact on our business, results of operations, financial condition and share price.

We expect our collaboration with Gilead to be a critical part of the development, manufacture and commercialization of our product candidates. If this collaboration is unsuccessful, our business could be adversely affected.

In October 2023, we entered into the Gilead Collaboration Agreement with Gilead, whereby Gilead exclusively licensed to us its HPI program and NNPI program, while retaining opt-in rights to these programs, and has an option

to take an exclusive license, on a program-by-program basis, to all of our other current and future pipeline programs during the collaboration term. In connection with the entry into the Gilead Collaboration Agreement, we and Gilead also entered into a common stock purchase agreement and an investor rights agreement, which were both amended in June 2024. Also in June 2024, we and Gilead subsequently entered into a securities purchase agreement and warrant agreement. In December 2024, Gilead purchased additional shares of our common stock at a premium pursuant to the terms of the common stock purchase agreement, and we amended the Gilead Collaboration Agreement in connection with an updated development plan for 6250. Our agreements and relationship with Gilead pose a number of risks, including, but not limited to, the following:

Nonclinical and clinical studies required for our product candidates are expensive and time-consuming and may fail to demonstrate the level of safety and efficacy necessary for product approval.

Before we or any commercial partners can obtain FDA approval (or other foreign approvals) necessary to sell any of our product candidates, we must show that each potential product is safe and effective. To meet these requirements, we must conduct extensive nonclinical and sufficient, well-controlled clinical studies.

The results of nonclinical studies may not be representative of disease behavior in a clinical setting and may not be predictive of the outcomes of our clinical studies. In addition, the results of early clinical studies of product candidates may not be predictive of the results of later-stage clinical studies.

Conducting nonclinical and clinical studies is a lengthy, time consuming and expensive process. The length of time varies substantially according to the type, complexity, novelty, and intended use of the product candidate, and often can be several years or more. In addition, failure or delays can occur at any time during the nonclinical and clinical study process, resulting in additional operating expenses or harm to our business.

The commencement and rate of completion of clinical studies might be delayed by many factors, including, for example:

The failure of nonclinical and clinical studies to demonstrate safety and effectiveness of a product candidate for the desired indications, whether conducted by us or by a CRO, would harm the development of that product candidate and potentially other product candidates. This failure could cause us to abandon a product candidate and could delay development of other product candidates. Any delay in, or failure of, our nonclinical studies or clinical studies could delay, or preclude, the filing of our NDAs and comparable applications with the FDA and foreign regulatory agencies, as applicable, and materially harm our business, prospects, financial condition and results of operations.

We rely on CROs to conduct some of our nonclinical and clinical studies due to our lack of suitable facilities and resources. In addition, parts of our business are reliant on CROs, vendors, suppliers and other service providers in locations outside of the United States, including China.

We do not have sufficient facilities or resources to conduct all our anticipated nonclinical and clinical studies internally. As a result, we contract with CROs to conduct a significant portion of the nonclinical and clinical studies required for regulatory approval for our product candidates. Our reliance on CROs reduces our control over these activities but does not relieve us of our responsibilities. For example, we are responsible for ensuring that each of our studies is conducted in accordance with the applicable protocol, legal and regulatory requirements and scientific standards, including, in the case of clinical studies, good clinical practices, even if the study is conducted by a CRO. In the event CROs fail to perform their duties in such a fashion or we are unable to retain or continue with CROs on acceptable terms, we may be unable to complete our clinical studies and may fail to obtain regulatory approval for our product candidates.

In addition, these CROs may also have relationships with other entities, some of which may be our competitors. CRO personnel are not our employees, and except for remedies available to us under our agreements with such third parties, we cannot control whether they devote sufficient time and resources to our clinical and nonclinical studies. If these CROs do not successfully carry out their contractual duties or obligations or meet expected deadlines, if they need to be replaced or if the quality or accuracy of the clinical data they obtain is compromised due to the failure to adhere to our clinical protocols, regulatory requirements, including good clinical practices, or for other reasons, our research, nonclinical or clinical studies may be extended, delayed or terminated and we may not be able to obtain, or may be delayed in obtaining, regulatory approvals for our product candidates, any of which could materially harm our business, prospects, financial condition and results of operations.

Furthermore, we are exposed to a number of risks related to our CROs, vendors, suppliers and other service providers that are located outside of the United States, many of which may be beyond our control. These risks include:

Top-line, preliminary or interim data may not accurately reflect the final results of a particular study.

We may publicly disclose top-line, preliminary or interim data based on analysis of then-available efficacy, tolerability, PK and safety data, and the results and related findings and conclusions are subject to change following a more comprehensive data review related to the particular study. We also may make assumptions, estimates, calculations and conclusions as part of our data analyses, and we may not have received or had the opportunity to fully and carefully evaluate all data prior to release. As a result, the top-line, preliminary or interim results that we report may differ from final results of the same studies or different conclusions or considerations may qualify such results once additional data have been received and fully evaluated. Top-line, preliminary or interim data also remain subject to audit and verification procedures that may result in the final data differing materially from previously published top-line, preliminary or interim data. As a result, top-line, preliminary or interim data should be viewed with caution until the final data are available.

In addition to top-line, preliminary or interim results, the information that we may publicly disclose regarding a particular nonclinical or clinical study is based on extensive information, and you or others may not agree with what we determine is the material or otherwise appropriate information to include in our disclosure. In addition, any information we determine not to disclose may ultimately be deemed significant with respect to future decisions, conclusions, views, activities or otherwise regarding a particular drug, drug candidate or our business. If the top-line, preliminary or interim data that we report differ from final results, or if others, including regulatory authorities, disagree with, or do not accept, the data or conclusions reached, our ability to obtain approval for, and commercialize, our product candidates may be harmed or delayed, which could harm our business, financial condition, operating results or prospects.

We rely on third parties to formulate and manufacture our product candidates and products that we study in combination with our product candidates. Our use of third parties may increase the risk that we will not have sufficient quantities of our product candidates or other products on time or at an acceptable cost.

We rely on third-party manufacturers to supply the quantities of our investigational product candidates used in our clinical and nonclinical studies. If any product candidate we develop or acquire in the future receives FDA or other regulatory approval, we expect to continue our reliance on one or more third-party contractors to manufacture our products. If, for any reason, we are unable to rely on any third-party sources we have identified to manufacture our product candidates, we would need to identify and contract with additional or replacement third-party manufacturers to manufacture drug substance and drug product for nonclinical, clinical and commercial purposes. We may be unsuccessful in identifying additional or replacement third-party manufacturers, or in negotiating acceptable terms with any that we do identify. If we are unable to establish and maintain manufacturing capacity, the development and sales of our products and our financial performance may be materially and adversely affected.

We are exposed to the following risks with respect to the manufacture of our product candidates:

Each of these risks could delay our development efforts, nonclinical studies and clinical studies or the approval, if any, of our product candidates by the FDA or applicable non-U.S. regulatory authorities and the commercialization of our product candidates. Furthermore, reductions in workforce at the FDA may lead to delays in inspecting facilities and, in turn, delayed FDA approvals for manufacturing changes. This could result in higher costs or deprive us of potential product revenues and materially harm our business, financial condition and results of operations.

If we lose key management personnel and cannot recruit and retain similarly qualified replacements, our business may materially suffer.

We are highly dependent on the services of our executive officers. Our employment agreements with our executive officers do not ensure their retention. We do not currently maintain, nor do we intend to obtain in the future, “key person” life insurance that would compensate us in the event of the death or disability of any of the members of our management team. Our executive officers are critical to our success, and unanticipated loss of any of these key employees could have a material adverse impact on our business, financial condition and results of operations.

Our collaboration partners might delay, prevent or undermine the success of our product candidates.

Our operating and financial strategy for the development, nonclinical and clinical testing, manufacture and commercialization of drug candidates heavily depends on collaborating with corporations, academic institutions, licensors, licensees, and other parties. However, there can be no assurance that we will successfully establish or maintain these collaborations. If a collaboration is terminated, replacement collaborators might not be available on attractive terms, or at all.

The activities of any collaborator, including Gilead, will not be within our control and might not be within our power to influence. There can be no assurance that any collaborator will perform its obligations to our satisfaction or at all, that we will derive any revenue or profits from these collaborations, or that any collaborator will not compete with us. If any collaboration, including the Gilead Collaboration, is unsuccessful, we might require substantially greater capital to undertake development and marketing of our proposed products and might not be able to develop and market these products effectively, if at all. In addition, if Gilead does not opt-in to a program, it might lead to significant delays in introducing proposed products into certain markets and/or reduced sales of proposed products in such markets.

We may not be successful in establishing and maintaining collaborations, which could adversely affect our ability to develop certain of our product candidates.

Developing pharmaceutical products, conducting clinical studies, obtaining regulatory approval and commercializing those products are expensive and lengthy undertakings that require significant resources and expertise. We may seek to enter into collaborations, including licensing or partnering arrangements, with other companies to support the development and commercialization of any or multiple of our programs that Gilead declines to opt into or to obtain financing or share costs on these programs. If we are unable to enter into such collaborations on acceptable terms, if at all, we may be unable to advance certain of our product candidates through further nonclinical or clinical development. We expect to face competition in seeking appropriate partners. Moreover, collaboration arrangements are complex and time consuming to negotiate, document and implement and they may require substantial resources to maintain. We may not be successful in our efforts to establish and implement collaborations or other alternative arrangements for the development of our product candidates that Gilead declines to opt into.

If we are unable to reach agreement on favorable terms with a suitable collaboration partner for any of our product candidates that Gilead declines to opt into, we may need to limit the number of our product candidates to advance through further nonclinical or clinical development. Failure to achieve such successful collaborations would limit our options for support of the development and commercialization of our programs and for financing and would likely have a material adverse impact on our business, results of operations, financial condition and share price.

We rely on data provided by third parties that has not been independently verified and could prove to be false, misleading, or incomplete.

We rely on third-party vendors, scientists, investigators and collaborators to provide us with significant data and other information related to our projects, nonclinical studies and clinical studies, and our business. If these third parties provide inaccurate, misleading, or incomplete data, our business, prospects, and results of operations could be materially and adversely affected.

Significant disruptions of information technology systems or breaches of data security, including cybersecurity incidents, could materially and adversely affect our business, results of operations and financial condition.

We collect and maintain information in digital form and are increasingly dependent on information technology systems and infrastructure to operate our business. In the ordinary course of our business, we collect, store and transmit large amounts of confidential information, including intellectual property, proprietary business information and personal information. It is critical that we do so in a secure manner to maintain the confidentiality and integrity of such confidential information. We have outsourced elements of our information technology infrastructure and, as a result, a number of third-party vendors may or could have access to our confidential information. Our internal information technology systems and infrastructure, and those of our current and any future collaborators, contractors and consultants and other third parties on which we rely, are vulnerable to damage from computer viruses, malware, natural disasters, system outages, terrorism, war, telecommunication and electrical failures, cyberattacks, cybersecurity

incidents or cyber intrusions over the Internet, attachments to emails, persons inside our organization, or persons with access to systems inside our organization.

The risk of a cybersecurity incident or security breach or disruption, particularly through cyberattacks or cyber intrusion, has escalated as the number, intensity and sophistication of attempted attacks and intrusions from around the world have increased. In addition, the prevalent use of mobile devices that access confidential information increases the risk of data security breaches, which could lead to the loss of confidential information or other intellectual property. The costs to us to mitigate network security problems, bugs, viruses, worms, malicious software programs, system outages and security vulnerabilities or incidents could be significant, and our efforts to address these problems may not be successful. If unsuccessful, these problems could cause interruptions, delays, cessation of service and other harm to our business and our competitive position, including material disruption of our product development programs. For example, any loss of clinical study data from completed or ongoing or planned clinical studies could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data.

If a computer security breach affects our systems or results in the unauthorized release of personally identifiable information, our reputation could be materially damaged. In addition, such a breach may require notification to governmental agencies, the media or individuals pursuant to various federal, state and non-U.S. privacy and security laws, if applicable, including the Health Insurance Portability and Accountability Act of 1996 (HIPAA), as amended by the Health Information Technology for Clinical Health Act of 2009, and its implementing rules and regulations, as well as regulations promulgated by the Federal Trade Commission, state breach notification law and the European Union (EU) General Data Protection Regulation (EU GDPR). We would also be exposed to a risk of loss or litigation and potential liability, which could materially adversely affect our business, results of operations and financial condition.

Research, development and commercialization goals, including data releases, may not be achieved in the timeframes that we publicly estimate, which could have an adverse impact on our business and could cause our stock price to decline.

We set goals and make public statements regarding our expectations on timing of certain accomplishments, developments and milestones under our research and development programs. The actual timing of these events can vary significantly due to a number of factors, including, the amount of time, effort and resources committed to our programs by us and any collaborators and the uncertainties inherent in the clinical development and regulatory approval process. As a result, there can be no assurance that we or any collaborators will initiate or complete clinical development activities, make regulatory submissions or receive regulatory approvals as planned or that we or any collaborators will be able to adhere to our current schedule for the achievement of key milestones under any of our programs. If we or any collaborators fail to achieve one or more of the milestones as planned, or Gilead does not opt-in to any of our programs, our business could be materially and adversely affected, and the price of our common stock could decline.

Developments by competitors might render our product candidates or technologies obsolete or non-competitive.

The pharmaceutical and biotechnology industries are intensely competitive. In addition, the clinical and commercial landscapes for recurrent genital herpes, HDV, HBV and transplant-related herpesviruses are rapidly changing; we expect new data from commercial and clinical-stage products to continue to emerge. We compete with organizations, some with significantly more resources, who are developing competitive product candidates. If our competitors develop effective treatments for recurrent genital herpes, HDV, HBV and transplant-related herpesviruses or any other indication or field we might pursue, and successfully commercialize those treatments, our business and prospects could be materially harmed.

Other companies with products using the same or similar mechanisms of action as ours may produce negative clinical data, which would adversely affect public and clinical communities’ perceptions of our product candidates, and may negatively impact regulatory approval of, or demand for, our potential products.

Negative data from clinical studies using a competitor’s product candidates with the same or similar mechanisms of action (MOA) as ours could adversely impact the perception of the therapeutic use of our product candidates and our ability to enroll individuals in clinical studies.

The clinical and commercial success of our potential products will depend in part on the public and clinical communities’ acceptance of novel classes of product candidates. Moreover, our success depends upon physicians prescribing, and their patients being willing to receive, treatments that involve the use of our product candidates we may develop in lieu of, or in addition to, existing treatments with which they are already familiar and for which more clinical data may be available. Adverse events in our nonclinical or clinical studies or those of our competitors or of academic researchers utilizing the same MOA as our product candidates, even if not ultimately attributable to our product candidates, and any resulting publicity could result in increased governmental regulation, larger, more complex, or an increased number of clinical trial requirements, unfavorable public perception, potential regulatory delays in the testing or approval of our product candidates, stricter labeling requirements for our product candidates that are approved, if any, and a decrease in demand for any such products.

Our ability to use our net operating loss and credit carryforwards and certain other tax attributes may be limited.

We have net operating loss carryforwards due to prior period losses generated before January 1, 2024, which if not utilized, will begin to expire in 2029 for net operating loss carryforwards prior to 2018. If we are unable to generate sufficient taxable income to utilize our net operating loss carryforwards, pre-2018 carryforwards could expire unused and be unavailable to offset future income tax liabilities.

Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended (the Code), a corporation that undergoes an “ownership change” (generally defined as a greater than 50% change (by value) in its equity ownership over a three-year period) is subject to annual limitations on its ability to use its pre-change net operating loss carryforwards and other pre-change tax attributes (such as research tax credits) to offset its post-change income or taxes. We have experienced ownership changes in the past, and future equity issuances may result in additional ownership change. Accordingly, some of our net operating losses or credits could expire unutilized, and our ability to utilize our net operating losses or credits to offset U.S. federal taxable income could be limited, which would result in increased future tax liability to us. We may also be subject to similar limitations at the state level.

We are and will be subject to extensive and costly government regulation, and the failure to comply with these regulations may have a material adverse effect on our operations and business.

Our product candidates are subject to extensive and rigorous domestic government regulation, including regulation by the FDA, the Centers for Medicare and Medicaid Services, other divisions of the U.S. Department of Health and Human Services, the U.S. Department of Justice, state and local governments, and their respective foreign equivalents. Both before and after approval of any product, we and our collaborators, suppliers, contract manufacturers and clinical investigators are subject to extensive regulation by governmental authorities in the United States and other countries, covering, among other things, testing, manufacturing, quality control, clinical studies, post-marketing studies, labeling, advertising, promotion, distribution, import and export, governmental pricing, price reporting and rebate requirements. Failure to comply with applicable requirements could result in one or more of the following actions: warning or untitled letters; unanticipated expenditures; delays in approval or refusal to approve a product candidate; voluntary or mandatory product recall; product seizure; interruption of manufacturing or clinical studies; operating or marketing restrictions; injunctions; criminal prosecution and civil or criminal penalties, including fines and other monetary penalties; exclusion from federal health care programs such as Medicare and Medicaid; adverse publicity; and disruptions to our business.

If we or our collaborators obtain regulatory approval for a particular product, the approval might limit the intended medical uses for the product, limit our ability to promote, sell, and distribute the product, require that we conduct costly post-marketing surveillance, and/or require that we conduct ongoing post-marketing studies. Once obtained, any approvals might be withdrawn, including, for example, if there is a later discovery of previously unknown problems with the product, such as a previously unknown safety issue. If we, our collaborators, our contractors or our contract manufacturers fail to comply with applicable regulatory requirements at any stage during the regulatory process, such noncompliance could result in delays in the approval of applications or supplements to approved applications, refusal by a regulatory authority (including the FDA) to review pending marketing authorization applications or supplements to approved applications, untitled letters or warning letters, fines, import and export restrictions, product recalls or seizures, injunctions, total or partial suspension of production, civil penalties, withdrawals of previously approved marketing authorizations, recommendations by the FDA or other regulatory authorities against governmental contracts, and/or criminal prosecutions.

The regulatory approval processes of the FDA and comparable foreign authorities are lengthy, time consuming and inherently unpredictable, and if we or our collaborators are ultimately unable to obtain regulatory approval for our product candidates, our business will be substantially harmed.

We, or any current or future collaborators, cannot assure you that we will receive the approvals necessary to commercialize for sale any of our product candidates, or any product candidate we acquire or develop in the future. We will need FDA approval to commercialize our product candidates in the United States and approvals from applicable regulatory authorities in foreign jurisdictions to commercialize our product candidates in those jurisdictions. To obtain FDA approval of any product candidate, we must submit to the FDA an NDA demonstrating that the product candidate is safe and effective for its intended use. This requires significant research, nonclinical studies, and clinical studies. Satisfaction of the FDA’s regulatory requirements typically takes many years, depends upon the type, complexity and novelty of the product candidate and requires substantial resources for research, development and testing. We cannot predict whether our research and clinical approaches will result in drugs that the FDA considers safe and effective for their indicated uses. The FDA has substantial discretion in the approval process and might require us to conduct additional nonclinical and clinical testing, perform post-marketing studies or otherwise limit or impose conditions on any approval we obtain.

The ability of the FDA to review and approve new products can be affected by a variety of factors, including government budget and funding levels, authorization and payment of user fees, the ability to hire and retain key personnel, as well as other statutory, regulatory and policy changes. In addition, funding of other government agencies that support research and development activities that pertain to FDA review, such as research to understand new technologies or establish new standards, can shift in response to changing administrative policies and priorities. Such policy shifts, including efforts to downsize the federal workforce, remove job elimination protections for federal workers, limit certain communications, and potentially interfere with user fee reauthorization, may affect the FDA review process and average review times at the FDA may fluctuate as a result. If a prolonged government shutdown or a widespread freeze on federal funding occurs, it could significantly impact the ability of the FDA to timely review and process our regulatory submissions, the National Institutes of Health to conduct research or provide grants, or other agencies that support the FDA to slow their work. In addition, if future legislation or administrative action or changes in FDA policy prevent the FDA or other regulatory authorities from conducting routine inspections, reviews, or other regulatory activities, it could significantly impact the ability of the FDA to timely review and process our regulatory submissions, which could have a material adverse effect on our business. Delays in obtaining regulatory approvals might: delay commercialization of, and our ability to derive product revenues from, our product candidates; impose costly procedures on us; and diminish any competitive advantages that we might otherwise enjoy.

Even if we comply with all FDA requests, the FDA might ultimately reject one or more of our NDAs. We cannot be sure that we will ever obtain regulatory approval and commercialize any of our current or future product candidates. In foreign jurisdictions, we are subject to regulatory approval processes and risks similar to those associated with the FDA described above. We cannot assure you that we will receive the approvals necessary to commercialize our product candidates for sale outside the United States.

We and our collaborators may be subject, directly or indirectly, to applicable U.S. federal and state anti-kickback, false claims laws, physician payment transparency laws, fraud and abuse laws or similar healthcare and security laws and regulations, and health information privacy and security laws, which could expose us or them to criminal sanctions, civil penalties, exclusion or suspension from federal and state healthcare programs, contractual damages, reputational harm and diminished profits and future earnings.

Healthcare providers, physicians and others play a primary role in the recommendation and prescription of any products for which we obtain regulatory approval. If we obtain FDA approval for any of our drug candidates and begin commercializing those drugs in the United States, our operations may be subject to various federal and state fraud and abuse laws, including the federal Anti-Kickback Statute, the federal False Claims Act, and physician payment sunshine laws and regulations. Additionally, we are subject to state and non-U.S. equivalents of each of the healthcare laws described above, among others, some of which may be broader in scope and may apply regardless of the payor. These laws may impact, among other things, our proposed sales, marketing and education programs. In addition, we may be subject to patient privacy regulation by both the federal government and the states and foreign jurisdictions in which we conduct our business. If we fail to comply with any applicable federal, state or foreign legal requirement, we could be subject to penalties.

Regulators globally are imposing greater monetary fines for privacy violations. The EU GDPR applies to any company established in the EU as well as to those outside the EU if they collect and use personal data in connection with the offering of goods or services to individuals in the EU or the monitoring of their behavior. The EU GDPR enhances

data protection obligations for processors and controllers of personal data, including, for example, expanded disclosures about how personal information is to be used, limitations on retention of information, mandatory data breach notification requirements and onerous new obligations on services providers. Noncompliance with the EU GDPR may result in monetary penalties of up to €20 million or 4% of worldwide revenue, whichever is higher. The EU GDPR may increase our responsibility and liability in relation to personal data that we process and we may be required to put in place additional mechanisms to ensure compliance with the EU GDPR, including as implemented by individual countries. Compliance with the EU GDPR and other changes in laws or regulations associated with the enhanced protection of certain types of personal data, such as healthcare data or other sensitive information, could greatly increase our cost of developing our products or even prevent us from offering certain products in jurisdictions that we may operate in.

The California Consumer Privacy Act (CCPA) also created new individual privacy rights for California consumers (as defined in the law) and places increased privacy and security obligations on entities handling personal data of consumers or households. The CCPA requires covered companies to provide certain disclosures to consumers about its data collection, use and sharing practices, and to provide affected California residents with ways to opt-out of certain sales or transfers of personal information. While there is currently an exception for protected health information that is subject to HIPAA and clinical study regulations, as currently written, the CCPA may impact our business activities. The uncertainty surrounding the implementation of the CCPA exemplifies the vulnerability of our business to the evolving regulatory environment related to personal data and protected health information.

Because of the breadth of these laws and the narrowness of the statutory exceptions and safe harbors available, it is possible that some of our business activities could be subject to challenge under one or more of such laws.

Violations of these laws may be punishable by criminal and/or civil sanctions, including penalties, fines and/or exclusion or suspension from federal and state healthcare programs such as Medicare and Medicaid and debarment from contracting with the U.S. government. In addition, private individuals have the ability to bring actions on behalf of the U.S. government under the federal False Claims Act as well as under the false claims laws of several states.

If any of the physicians or other providers or entities with whom we expect to do business with are found to be not in compliance with applicable laws, they may be subject to criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs, which may also adversely affect our business.

We face the risk of product liability claims and might not be able to obtain insurance.

Our business exposes us to the risk of product liability claims that are inherent in drug development. If the use of one or more of our product candidates or approved drugs, if any, harms people, we might be subject to costly and damaging product liability claims brought against us by clinical study participants, consumers, health care providers, pharmaceutical companies or others selling our products. Our inability to obtain sufficient product liability/clinical study insurance at an acceptable cost to protect against potential product liability claims could prevent or inhibit the commercialization of pharmaceutical products we develop. We cannot predict all of the possible harms or side effects that might result and, therefore, the amount of insurance coverage we maintain might not be adequate to cover all liabilities we might incur. If we are unable to obtain insurance at an acceptable cost or otherwise protect against potential product liability claims, we will be exposed to significant liabilities, which might materially and adversely affect our business and financial position. If we are sued for any injury allegedly caused by our products, our liability could exceed our total assets and our ability to pay. Any successful product liability claims brought against us would decrease our cash and may adversely affect our business, stock price and financial condition.

We might be exposed to liability claims associated with the use of hazardous materials and chemicals.

Our research, development and manufacturing activities and/or those of our third-party contractors might involve the controlled use of hazardous materials and chemicals. Although we will strive to have our safety procedures, and those of our contractors, comply with federal, state and local laws and regulations for using, storing, handling and disposing of these materials, we cannot completely eliminate the risk of accidental injury or contamination from these materials. In the event of such an accident, we could be held liable for any resulting damages, and any liability could materially and adversely affect our business, financial condition and results of operations. In addition, the federal, state and local laws and regulations governing the use, manufacture, storage, handling and disposal of hazardous or radioactive materials and waste products might require us to incur substantial compliance costs that could materially and adversely affect our business, financial condition and results of operations.

Our employees, independent contractors, consultants, collaborators and CROs may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements, which could result in significant liability for us and harm our reputation.

Misconduct could also involve the improper use or misrepresentation of information obtained during clinical studies, creating fraudulent data in our nonclinical studies or clinical studies or illegal misappropriation of product materials, which could result in regulatory sanctions, delays in clinical studies, or serious harm to our reputation.

It is not always possible to identify and deter misconduct. The precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with such laws or regulations. Additionally, we are subject to the risk that a person or government could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us and we are not successful in defending ourselves or asserting our rights, those actions could harm our business, results of operations, financial condition and cash flows, including through the imposition of significant fines or other sanctions.

If we, our licensors and our collaborators do not obtain protection for our respective intellectual property rights, our competitors might be able to take advantage of our research and development efforts to develop competing drugs. Our success, competitive position and future revenues, if any, depend in part on our ability and the abilities of our licensors to obtain and maintain patent protection for our products, methods, processes and other technologies, to preserve our trade secrets, to prevent third parties from infringing on our proprietary rights and to operate without infringing the proprietary rights of third parties.

We rely upon a combination of patents, trade secret protection and contractual arrangements to protect the intellectual property related to our technologies. We will only be able to protect our products and proprietary information and technology by preventing unauthorized use by third parties to the extent that our patents, trade secrets, and contractual positions allow us to do so. We cannot be certain that we will secure any rights to any issued patents with claims that cover any of our proprietary product candidates and technologies. The patent prosecution process is expensive and time-consuming, and we may be unable to file and prosecute all necessary or desirable patent applications at a reasonable cost or in a timely manner. We could fail to identify patentable aspects of our research and development output before it is too late to obtain patent protection or before our competitors secure patents covering such discoveries. The patent process also is subject to numerous risks and uncertainties, and there can be no assurance that we will be successful in protecting our products by obtaining and defending patents.

Composition-of-matter patents relating to the active pharmaceutical ingredient are generally considered to be the strongest form of intellectual property protection for pharmaceutical products. Such patents provide protection not limited to any one method of use. Method-of-use patents protect the use of a product for the specified method(s) and do not prevent a competitor from making and marketing a product that is identical to our product for an indication that is outside the scope of the patented method. Formulation patents protect the formulation of a product and do not prevent a competitor from making and marketing a product that has an identical active pharmaceutical ingredient to

our product if the product is formulated differently than the patented formulation. We rely on a combination of these and other types of patents to protect our product candidates, and there can be no assurance that our intellectual property will create and sustain the competitive position of our product candidates.

Biotechnology and pharmaceutical product patents involve highly complex legal and scientific questions. Any patent applications that we own or license may fail to result in issued patents. In addition, the U.S. Patent and Trademark Office (USPTO) and patent offices in other jurisdictions often require that patent applications concerning pharmaceutical and/or biotechnology-related inventions are limited or narrowed substantially to cover only the specific innovations exemplified in the patent application, thereby limiting the scope of protection against competitive challenges. As a result, even if we or our licensors obtain patents, the patents might be substantially narrower than anticipated.

If patents successfully issue from our applications, third parties may challenge their validity or enforceability, which may result in such patents being narrowed, invalidated, or held unenforceable. Even if our patents and patent applications are not challenged by third parties, those patents and patent applications may not prevent others from designing around our claims and may not otherwise adequately protect our product candidates.

Patent and other intellectual property protection is crucial to the success of our business and prospects, and there is a substantial risk that such protections, if obtained, will prove inadequate. The legal systems of certain countries, including China, do not always favor the enforcement of patents, trade secrets, and other intellectual property rights, particularly those relating to pharmaceutical and biotechnology products, which could make it difficult for us to stop infringement of our patents, misappropriation of our trade secrets, or marketing of competing products in violation of our proprietary rights.

Beyond the protection afforded by patents, we seek to rely on trade secret protection and confidentiality agreements to protect proprietary know-how, information, or technology that is not covered by our patents. Although our agreements require all of our employees to assign their inventions to us, and we require all of our employees, consultants, advisors, collaborators, contractors and any third parties who have access to our trade secrets, proprietary know-how and other confidential information and technology to enter into appropriate confidentiality agreements, we cannot be certain that our trade secrets, proprietary know-how and other confidential information and technology will not be subject to unauthorized disclosure or that our competitors will not otherwise gain access to or independently develop substantially equivalent trade secrets, proprietary know-how and other information and technology. If we are unable to prevent unauthorized disclosure of our intellectual property related to our product candidates and technology to third parties, we may not be able to establish or maintain a competitive advantage in our market, which could materially adversely affect our business and operations.

We may incur substantial costs as a result of litigation or other proceedings relating to our patents and other intellectual property rights.

We may in the future be involved in legal or administrative proceedings involving our intellectual property, including infringement of our intellectual property by third parties. These lawsuits or proceedings likely would be expensive, consume time and resources and divert the attention of managerial and scientific personnel, even if we were successful in stopping the infringement of such patents. There is a risk that these proceedings will decide that such patents or other intellectual property rights are not valid and that we do not have the right to stop the other party from using our inventions. There is also the risk that, even if the validity of such patents is upheld, the court or administrative agency will refuse to stop the other party on the ground that such other party’s activities do not infringe our rights to such patents. If we were not successful in defending our intellectual property, our competitors could develop and market products based on our discoveries, which may reduce demand for our products.

We may infringe the intellectual property rights of others, which may prevent or delay our product development efforts and stop us from commercializing or increase the costs of commercializing our product candidates.

Our success will depend in part on our ability to operate without infringing the proprietary rights of third parties. Our competitors may have filed, and may in the future file, patent applications covering products and technologies similar to ours. Any such patent application may have priority over our patent applications, which could further require us to obtain rights from third parties to issued patents covering such products and technologies. We cannot guarantee that the manufacture, use or marketing of any product candidates that we develop will not infringe third-party patents.

If a patent infringement suit were brought against us, we may be forced to stop or delay developing, manufacturing, or selling potential products that are claimed to infringe a third party’s intellectual property, unless that third party grants us rights to use its intellectual property. In such cases, we may be required to obtain licenses to patents or proprietary rights of others to continue development, manufacture or sale of our products. If we are unable to obtain a license or develop or obtain non-infringing technology, or if we fail to defend an infringement action successfully, or if we are found to have infringed a valid patent, we may incur substantial costs and monetary damages, encounter significant delays in bringing our product candidates to market and be precluded from manufacturing or selling our product candidates, any of which could harm our business significantly.

The cost of maintaining our patent protection globally is high and requires continuous review and compliance. We may not be able to effectively maintain our intellectual property position throughout the major markets of the world.

The USPTO and foreign patent authorities require maintenance fees, payments and continued compliance with a number of procedural and documentary requirements. Noncompliance may result in abandonment or lapse of patents or patent applications and a partial or complete loss of patent rights in the relevant jurisdiction. Such a loss could reduce royalty payments for lack of patent coverage from our collaboration partners or may result in competition, either of which could have a material adverse effect on our business.

We have made, and will continue to make, certain strategic decisions in balancing the costs and the potential protections afforded by the patent laws of certain countries. As a result, we may not be able to prevent third parties from practicing our inventions in all countries, or from selling or importing products made using our inventions in and into the United States or other countries. Third parties may use our technologies in territories in which we have not obtained patent protection to develop their own products and may infringe our patents in territories which provide inadequate enforcement mechanisms. Such third-party products may compete with our product candidates, and our patents or other intellectual property rights may not be effective or sufficient to prevent them from competing. Such competition could materially and adversely affect our business and financial condition.

Intellectual property rights do not address all potential threats to any competitive advantage we may have.

The degree of future protection afforded by our intellectual property rights is uncertain because intellectual property rights have limitations, and intellectual property rights may not adequately protect our business or permit us to maintain our competitive advantage. The following examples are illustrative:

The price of our common stock might fluctuate significantly, and you could lose all or part of your investment.

The price of our common stock fluctuates widely. Continued volatility in the market price of our common stock might prevent a stockholder from being able to sell shares of our common stock at or above the price paid for such shares. The trading price of our common stock may continue to be volatile and subject to wide price fluctuations in response to various factors, many of which are beyond our control, such as the progress, results and timing of our clinical and nonclinical studies and other studies involving our product candidates, the success or failure of our product candidates, the receipt or loss of required regulatory approvals for our product candidates, the availability of capital or the other risks discussed in this “Risk Factors” section.

Our amended and restated bylaws provide that the Court of Chancery of the State of Delaware will be the sole and exclusive forum for certain types of actions and proceedings that may be initiated by our stockholders, which could limit our stockholders’ ability to bring a claim in a judicial forum they find favorable for disputes with us or our directors, officers or other employees.

Our amended and restated bylaws provide that, with certain limited exceptions, unless we consent to the selection of an alternative forum, the Court of Chancery of the State of Delaware is the sole and exclusive forum for (1) any derivative action or proceeding brought on our behalf; (2) any action asserting a claim of breach of fiduciary duty owed by any of our current or former directors, officers or other employees to us or to our stockholders; (3) any action asserting a claim arising pursuant to the Delaware General Corporation Law, or our certificate of incorporation or bylaws (as each may be amended from time to time); or (4) any action asserting a claim governed by the internal affairs doctrine. Alternatively, if such court does not have jurisdiction, the Superior Court of Delaware, or, if such other court does not have jurisdiction, the United States District Court for the District of Delaware, will be the sole and exclusive forum for such actions and proceedings. The choice of forum provision may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or our directors, officers, or other employees, which may discourage such lawsuits against us and our directors, officers, and other employees. Alternatively, if a court were to find the choice of forum provision contained in our amended and restated bylaws to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which could have a material adverse impact on our business. The choice of forum provision in our amended and restated bylaws will not preclude or contract the scope of exclusive federal or concurrent jurisdiction for actions brought under the federal securities laws, including the Exchange Act or the Securities Act, or the respective rules and regulations promulgated thereunder.

We lease office space for corporate and administrative functions and laboratory space in South San Francisco, California under a sublease that expires in September 2029.

We believe these leased facilities are adequate for our current needs and that additional space will be available in the future on commercially reasonable terms as needed.

We are not a party to any material legal proceedings at this time. From time to time, we may be subject to various legal proceedings and claims that arise in the ordinary course of our business activities. Although the results of litigation and claims cannot be predicted with certainty, we do not believe we are party to any claim or litigation the outcome of which, if determined adversely to us, would individually or in the aggregate be reasonably expected to have a material adverse effect on our business. Regardless of the outcome, litigation can have an adverse effect on us because of defense and settlement costs, diversion of management resources and other factors.

Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities

Our common stock is traded under the symbol “ASMB” and is quoted on The Nasdaq Global Select Market.

As of March 14, 2025, there were 49 stockholders of record, which excludes stockholders whose shares were held in nominee or street name by brokers.

We have never declared or paid any dividends and do not anticipate paying any dividends on our common stock in the foreseeable future.

We did not purchase any of our registered equity securities during the period covered by this Annual Report on Form 10-K.

On January 31, 2024, following approval by our stockholders, our board of directors approved the implementation of a reverse stock split of our common stock at a ratio of 1-for-12 (the Reverse Stock Split). The Reverse Stock Split was effective as of February 9, 2024, and our common stock began trading on the Nasdaq Global Select Market on a post-split basis on February 12, 2024. All share and per share amounts of our common stock presented in this Annual Report on Form 10-K have been adjusted to reflect the Reverse Stock Split.

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our consolidated financial statements and the related notes thereto and other financial information appearing elsewhere in this Annual Report on Form 10-K. The following discussion contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those expressed or implied in any forward-looking statements as a result of various factors, including those set forth in this Form 10-K under “Item 1A. Risk Factors.”

In addition, during December 2024, we identified a development candidate, 7423, in our broad-spectrum NNPI program targeting transplant-associated herpesviruses.

HPIs are active against TK-deficient HSV-1 and HSV-2, which is a major mechanism of resistance to nucleoside analogs.

We expect interim data from the Phase 1b portion of the 5366 study to be available in fall 2025.

evaluated as of the February 13, 2025 data cutoff date, 1179 had a mean half-life of approximately four days when dosed orally, supporting once-weekly oral dosing, the target profile for 1179.

transport of bile acids. The binding of specific small or large molecules to NTCP has been shown to effectively inhibit the interaction of HBsAg with NTCP, which prevents HBV and HDV from infecting hepatocytes.

We initiated a Phase 1a clinical study of 6250 during the fourth quarter of 2024, and we expect interim safety, PK and biomarker data from single-ascending and multiple-ascending doses cohorts in healthy participants in the third quarter of 2025.

HBV is a DNA virus that infects hepatocytes and establishes a reservoir of covalently closed circular DNA (cccDNA), a unique viral DNA moiety that resides in the nucleus of HBV-infected hepatocytes and is associated with viral persistence and chronic infection. No currently approved oral therapies target cccDNA activity directly. As a result, we have worked to discover and develop compounds targeting the core protein, a viral protein involved in numerous aspects of the HBV replication cycle, including the generation of HBV cccDNA.

maintained clinical exposures multiple folds above those anticipated to be required for potent viral activity and inhibition of cccDNA formation. A mean decline in HBV DNA of 2.9 log10 IU/mL was observed in a population of predominately HBeAg negative participants. Among the subset of participants with detectable HBV RNA at baseline, a mean decline of 2.5 log10 U/mL for HBV RNA was observed. As anticipated, limited changes in viral antigens were observed for the study population over the 28-day treatment period. These initial antiviral data are consistent with the high potency seen preclinically for 4334. The interim safety data also demonstrated that 4334 was well-tolerated with a favorable safety profile observed. Enrollment is ongoing for the second cohort, evaluating an oral once-daily 400 mg dose of 4334. Based on the strong antiviral activity observed in the first cohort, we expect that the 400 mg cohort will be the final cohort for this Phase 1b study. We anticipate releasing data from the 400 mg cohort in the first half of 2025.

In December 2024, we nominated 7423 as our development candidate to undergo CTA-enabling studies, which are ongoing.

Since our inception, we have had no revenue from product sales and have funded our operations principally through debt financings prior to our initial public offering in 2010 and through equity financings and collaborations since then. Our operations to date have been primarily limited to organizing and staffing our company, discovering and developing our product candidates, licensing our product candidates, maintaining and improving our patent portfolio and raising capital.

We have generated significant losses to date, and we expect to continue to generate losses as we develop our product candidates. As of December 31, 2024, we had an accumulated deficit of $825.9 million. Because we do not generate revenue from any of our product candidates, our losses will continue as we further develop and seek regulatory approval for, and commercialize, our product candidates. Additionally, we expect our research and development expenses to increase over the coming years as we continue the development of our product candidates. As a result, our operating losses are likely to be substantial over the next several years and thereafter if none of our product

candidates are approved or successfully launched. We are unable to predict the extent of any future losses or when we will become profitable, if at all.

Our management’s discussion and analysis of our financial condition and results of operations is based on our consolidated financial statements, which we have prepared in accordance with accounting principles generally accepted in the United States. The preparation of these consolidated financial statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenues and expenses during the reporting periods. Note 2 to the Consolidated Financial Statements describes the significant accounting policies and methods used in the preparation of our consolidated financial statements.

We evaluate our estimates and judgments on an ongoing basis. We base our estimates on historical experience and on various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

We analyze our collaboration arrangements to assess whether such arrangements, or transactions between arrangement participants, involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities or are more akin to a vendor-customer relationship. In making this evaluation, we consider whether the activities of the collaboration are considered to be distinct and deemed to be within the scope of the collaborative arrangement accounting standard and those that are more reflective of a vendor-customer relationship and, therefore, within the scope of the revenue with contracts with customers accounting standard. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement.

For arrangements or transactions between arrangement participants determined to be within the scope of the contracts with customers accounting standard, we evaluate the term of the arrangement and recognize revenue when the customer obtains control of promised goods or services in a contract for an amount that reflects the consideration we expect to receive in exchange for those goods or services. For contracts with customers, we apply the following five-step model, each of which requires judgment, in order to determine this amount: (1) identification of the promised goods or services in the contract; (2) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (3) measurement of the transaction price, including the constraint on variable consideration; (4) allocation of the transaction price to the performance obligations; and (5) recognition of revenue when (or as) we satisfy each performance obligation.

We only apply the five-step model to contracts when it is probable we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. As part of the accounting for contracts with customers, we must develop assumptions that require judgment to determine the estimated relative standalone selling price (SSP) of each performance obligation identified in the contract. We then allocate the total transaction price to each performance obligation based on its SSP and recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when or as the performance obligation is satisfied.

We account for contract modifications, defined as changes in the scope or price (or both) of a contract that are approved by the parties to the contract, such as a contract amendment, when the parties to a contract approve a modification that either creates new, or changes existing, enforceable rights and obligations of the parties to the contract. We use one of the following methods depending on facts and circumstances: (i) as a separate contract if the modification adds distinct goods or services and the price reflects the SSP of those additional goods or services; (ii) as a termination of the existing contract and creation of a new contract if the remaining goods or services are distinct from those transferred before the modification; or (iii) as a cumulative catch-up adjustment to the original contract if the remaining goods or services are not distinct from those transferred before the modification.

For recognition of revenue relating to the Gilead Collaboration Agreement at commencement of the arrangement, we determined the transaction price and allocated it to a single combined performance obligation, the discovery, research and development services during the collaboration term. We estimated the SSP of extension fees and opt-in rights pursuant to the Gilead Collaboration Agreement using significant estimates, including forecasted revenues and costs, development timelines, discount rates, and probabilities of technical and regulatory success. We concluded none of the options in the contract are performance obligations at the outset of the arrangement as they are contingent upon

option exercise, are capable of being distinct from the research and development services and are not offered at a discount to their SSP.

We determined the First Amendment to the Gilead Collaboration Agreement represents a contract modification within the scope of the revenue from contracts with customers guidance. We concluded there continues to be a single combined performance obligation consisting of a series of distinct research and development services, and therefore, the remaining services under the First Amendment to the Gilead Collaboration Agreement are distinct from the research and development services already provided. Accordingly, we accounted for the First Amendment as a termination of the existing contract and the creation of a new contract and are recognizing the revenue on a prospective basis by reassessing the transaction price and allocating it to the remaining research and development services.

We evaluate each performance obligation to determine if it can be satisfied at a point in time or over time, and we measure the services delivered to the customer, which we periodically review based on the progress of the related program. We recognize revenue under the Gilead Collaboration Agreement over time using a cost-based input method, which continues to be appropriate following the First Amendment to the Gilead Collaboration Agreement. Revenue related to certain performance obligations that are satisfied over time could be materially impacted as a result of changes in the estimated total research effort required to satisfy those obligations. A hypothetical 10% change in the total estimated effort required to satisfy the single combined performance obligation related to the Gilead Collaboration Agreement would have changed the related revenue recognized during the year ended December 31, 2024 by as much as $3.5 million. The effect of any change made to an estimated input component and, therefore revenue recognized, would be recorded as a change in estimate. Such changes in estimate could have a material impact on the revenue recognized in a future period. In addition, variable consideration (including regulatory and commercial milestones) must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price.

As part of the process of preparing our consolidated financial statements, we are required to estimate certain research and development expenses. This process involves reviewing quotations and contracts, reviewing the terms of our license agreements, communicating with our vendors and applicable personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. Such payments are evaluated for current or long-term classification based on when they will be realized or consumed. Examples of estimated amortized or accrued research and development expenses include fees to:

We base our expenses related to clinical studies on our estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and CROs that conduct and manage clinical studies on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows and expense recognition. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In either amortizing or accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the related prepayment or accrual accordingly. Our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in our reporting changes in estimates in any particular period. Adjustments to prior period estimates have not been material for the years ended December 31, 2024 and 2023.

The following table summarizes the period-over-period changes in our collaboration revenue (in thousands, except for percentages):

Collaboration revenue was $28.5 million for the year ended December 31, 2024 compared to $7.2 million for the year ended December 31, 2023. The $21.4 million increase in collaboration revenue was driven by recognizing a full year of revenue in 2024 under the Gilead Collaboration Agreement, which was entered into in October 2023. Collaboration revenue for 2023 also includes recognizing the remaining $2.7 million of deferred revenue under our Collaboration Agreement with BeiGene, Ltd. (BeiGene) upon our discontinuing development of ABI-H3733 (3733), which left no products licensed to BeiGene and no remaining performance obligations.

Research and development expenses consist primarily of employee-related expenses, fees paid to CROs and CMOs, lab supplies and other third-party expenses that support our research and discovery, nonclinical and clinical activities. External costs represent a significant portion of our research and development expenses, which we track on a program-by-program basis following the nomination of a development candidate. We use our employee and infrastructure resources, as well as certain third-party costs, across multiple research and development programs, and we do not specifically allocate these costs to our programs.

The following table summarizes the period-over-period changes in our research and development expenses (in thousands, except for percentages):

(1) Reflects net amounts refundable to us after the final reconciliation of costs of the clinical trial conducted pursuant to the Clinical Trial Collaboration Agreement with Arbutus Biopharma Corporation, which was terminated in February 2023.

Research and development expenses were $55.9 million for the year ended December 31, 2024 compared to $48.9 million for the year ended December 31, 2023. The $7.0 million increase in research and development expenses was primarily driven by increases in external program expenses from the advancement and expansion of our pipeline, most notably from our recurrent genital herpes programs, 1179 and 5366, as well as our HDV entry inhibitor, 6250. These increases in external expenses were partially offset by savings from our discontinuation of 3733 and VBR. We also experienced a $0.9 million increase in employee and contractor-related expenses due to higher headcount and increased travel costs as a result of having an expanded pipeline with more candidates entering the clinic in 2024. The

overall increase was further offset by a $1.9 million decrease in our facility and other expenses, reflecting cost savings in rent and related expenses from our corporate headquarters sublease, which commenced in November 2023.

General and administrative expenses consist primarily of salaries and other related costs for personnel in executive, finance, accounting, business development, information technology, legal and human resources functions. Other significant costs include facility costs not otherwise included in research and development expenses, insurance costs, legal fees relating to patents and corporate matters and fees for accounting and consulting services.

The following table summarizes the period-over-period change in our general and administrative expenses (in thousands, except for percentages):

General and administrative expenses were $18.0 million for the year ended December 31, 2024, compared to $22.9 million for the year ended December 31, 2023. The $4.9 million decrease in general and administrative expenses was primarily due to higher legal expenses incurred in 2023 related to the Gilead Collaboration, as well as higher stock-based compensation expense in 2023, mainly resulting from the vesting of restricted stock awards with performance based-vesting conditions.

Interest income consists of interest earned on our cash and cash equivalents and available-for-sale marketable securities.

The following table summarizes the period-over-period changes in our interest and other income, net (in thousands, except for percentages):

Interest and other income, net was $5.6 million for the year ended December 31, 2024, compared to $3.5 million for the year ended December 31, 2023. The increase of $2.1 million was primarily due to more interest income earned on marketable securities resulting from having a larger portfolio balance after the receipt of $100.0 million upon entering into the Gilead Collaboration in October 2023 and multiple equity financings entered into in 2024.

The following table summarizes the period-over-period changes in our income tax expense (in thousands, except for percentages):

Income tax expense was $0.3 million for the year ended December 31, 2024 due to taxable income incurred from the upfront payments received under the Gilead Collaboration in 2023. Income tax expense was insignificant during the year ended December 31, 2023.

As a result of our significant research and development expenditures and the lack of any FDA-approved products to generate product sales revenue, we have not been profitable and have generated operating losses since we were incorporated in October 2005. We have funded our operations through December 31, 2024 principally through equity

financings, raising an aggregate of $648.0 million in net proceeds, and strategic collaborations, raising an aggregate of $200.9 million.

We expect our future operating expenses to increase substantially over the coming years as we continue to advance our candidates into the clinic. We monitor our cash needs and the status of the capital markets on a continuous basis. From time to time, we opportunistically raise capital and have done so numerous times since our initial public offering by issuing equity securities. We expect to continue to raise capital when and as needed and at the time and in the manner most advantageous to us.

We expect our existing cash, cash equivalents and marketable securities will enable us to fund our operations into the middle of 2026. We have based this estimate on assumptions that may prove to be wrong, and we may utilize our available capital resources sooner than we currently expect. Our contractual obligations include operating lease obligations totaling $3.9 million as of December 31, 2024, of which $0.8 million are short-term. We also enter into contracts in the normal course of business with CROs for clinical trials and CMOs for clinical supply manufacturing and with vendors for nonclinical research studies and other services and products for operating purposes, which generally provide for termination within 30 days of notice.

Identifying potential product candidates and conducting nonclinical testing and clinical studies is a time-consuming, expensive and uncertain process that takes years to complete, and we may never generate the necessary data or results required to obtain marketing approval and achieve product sales. In addition, our product candidates, if approved, may not achieve commercial success. Our commercial revenues, if any, will likely be derived from sales of medicines that we do not expect to be commercially available for years, if at all. Accordingly, we will need to continue to rely on additional financings to achieve our business objectives. Adequate additional financings may not be available to us on acceptable terms, or at all. To the extent that we raise additional capital through the sale of equity, the ownership interest of our stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders. Debt financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we are unable to raise additional funds when needed, we may be required to reduce staff, delay, scale back or discontinue our product development and clinical studies or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

The following table summarizes our cash flows for the periods presented (in thousands):

Net cash used in operating activities for the year ended December 31, 2024 was $51.1 million, compared to net cash provided by operating activities of $22.7 million for the same period in 2023. The decrease in operating cash flows was primarily due to $90.7 million received under the Gilead Collaboration Agreement in 2023, partially offset by cost savings in rent and related expenses attributable to our corporate headquarters sublease, which commenced in November 2023, and the timing of vendor invoicing and payments.

Net cash provided by investing activities for the year ended December 31, 2024 was $40.2 million, compared to net cash used in investing activities of $69.1 million for the same period in 2023. The increase in cash flows from investing was due to higher proceeds from maturities of our marketable securities, which exceeded purchases in 2024. In contrast, in 2023 our purchases of marketable securities exceeded proceeds because of additional funds available to invest from the upfront payment received from Gilead under the Gilead Collaboration Agreement.

Net cash provided by financing activities for the year ended December 31, 2024 was $29.4 million, compared to $13.8 million for the same period in 2023. The increase in financing cash flows was primarily driven by the sale of 0.6 million more shares of our common stock through multiple equity financings in 2024 and at an increased price per share compared to 2023.

The financial statements required to be filed pursuant to this Item 8 are appended to this report. An index of those financial statements is found on page F-1.

Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure

We maintain a system of disclosure controls and procedures, as defined in Rule 13a-15(e) promulgated under the Securities and Exchange Act of 1934, as amended (the Exchange Act), that is designed to provide reasonable assurance that information, which is required to be disclosed in our reports filed pursuant to the Exchange Act, is accumulated and communicated to management in a timely manner. At the end of fiscal year ending December 31, 2024, we carried out an evaluation, under the supervision, and with the participation of, our management, including our Chief Executive Officer and President, who serves as our principal executive officer and principal financial officer, of the effectiveness of the design and operation of our disclosure controls and procedures pursuant to Exchange Act Rule 13a-15(b). Based upon that evaluation, our Chief Executive Officer and President concluded that our disclosure controls and procedures for the fiscal year ending as of December 31, 2024 were effective at reasonable assurance levels.

Our management is responsible for establishing and maintaining adequate internal control over financial reporting, as such term is defined in Exchange Act Rule 13a-15(f). Our internal control over financial reporting is designed to provide reasonable assurance to our management and board of directors regarding the preparation and fair presentation of published financial statements. A control system, no matter how well designed and operated, can only provide reasonable, not absolute, assurance that the objectives of the control system are met. Because of these inherent limitations, management does not expect that our internal controls over financial reporting will prevent all error and all fraud. Under the supervision and with the participation of our management, including our Chief Executive Officer and President, who serves as our principal executive officer and principal financial officer, we conducted an evaluation of the effectiveness of our internal control over financial reporting based on the framework in Internal Control-Integrated Framework issued in 2013 by the Committee of Sponsoring Organizations of the Treadway Commission. Based on our evaluation under the framework in Internal Control-Integrated Framework, our management concluded that our internal control over financial reporting was effective as of December 31, 2024.

There were no changes in our internal control over financial reporting in the fourth quarter of 2024 that materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

Except as set forth below, the information required by this item will be contained in our definitive proxy statement to be filed with the SEC in connection with the Annual Meeting of Stockholders (Proxy Statement) within 120 days after the conclusion of our fiscal year ended December 31, 2024 and is incorporated in this Annual Report on Form 10-K by reference.

Our Board has adopted a Code of Ethics for our principal executive officer and all senior financial officers and a Code of Conduct applicable to all of our employees and our directors. Both Codes are available under the “Investors—Corporate Governance” section of our website at www.assemblybio.com. If we make any substantive amendments to, or grant any waivers from, the Code of Ethics for our principal executive officer, principal financial officer, principal accounting officer, controller or persons performing similar functions, or any officer or director, we will disclose the nature of such amendment or waiver on our website or in a Current Report on Form 8-K.

The information required by this item will be contained in the Proxy Statement and is incorporated into this Annual Report on Form 10-K by reference.

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters

Except for the table regarding equity compensation plans, the information required by this item will be contained in the Proxy Statement and is incorporated into this Annual Report on Form 10-K by reference.

The following table sets forth the indicated information as of December 31, 2024 with respect to our equity compensation plans.

Our stockholder-approved equity compensation plans consist of the 2018 Plan, the 2014 Plan, the 2010 Plan and the 2018 ESPP. Effective on June 2, 2016, the 2010 Plan was frozen, and no further grants will be made under the 2010 Plan. Shares that are forfeited under the 2010 Plan on or after June 2, 2016 will become available for issuance under the 2014 Plan. An “Award” under the 2018 Plan, 2014 Plan or 2010 Plan is any right to receive our common stock consisting of non-statutory stock options, incentive stock options, stock appreciation rights, RSUs, or any other stock award.

In May 2018, our stockholders approved the 2018 ESPP and it was amended and restated in May 2021 and May 2024. The 2018 ESPP provides for the purchase by employees of up to an aggregate of 226,398 shares of the Company’s common stock. Eligible employees can purchase shares of our common stock at the end of a predetermined offering period at 85% of the lower of the fair market value at the beginning or end of the offering period.

Our outstanding equity compensation arrangements that have not been approved by our stockholders consist of the 2017 Inducement Plan, the 2019 Inducement Plan, the 2020 Inducement Plan and warrants granted in a registered direct offering and a private placement in June 2024. In April 2017, our board of directors adopted the 2017 Inducement Plan and reserved 66,666 shares of our common stock for issuance under the 2017 Inducement Plan. In August 2019, our board of directors adopted the 2019 Inducement Plan and reserved 41,666 shares of our common stock for issuance under the 2019 Inducement Plan. In March 2020, our board of directors adopted the 2020 Inducement Plan and reserved 66,666 shares of our common stock for issuance under the 2020 Inducement Plan. The only persons eligible to receive grants of awards under the 2017 Inducement Plan, the 2019 Inducement Plan or the 2020 Inducement Plan are individuals who satisfy the standards for inducement grants under Nasdaq Marketplace Rule 5635(c)(4) and the related guidance under Nasdaq IM 5635-1-that is, generally, a person not previously an employee or director of ours, or following a bona fide period of non-employment, as an inducement material to the individual's entering into employment with us. An “Award” is any right to receive our common stock pursuant to the Inducement Plan, consisting of nonstatutory stock options, stock appreciation rights, restricted stock awards, RSUs, or any other stock award.

Item 13. Certain Relationships and Related Party Transactions, and Director Independence

The information required by this item will be contained in the Proxy Statement and is incorporated into this Annual Report on Form 10-K by reference.

(a) Exhibits. The following exhibits are filed as part of this Annual Report on Form 10-K:

† The schedules to this exhibit have been omitted pursuant to Item 601(a)(5) of Regulation S-K.

‡ Portions of this exhibit have been omitted pursuant to Item 601(b)(10)(iv) of Regulation S-K.

** The certification attached as Exhibit 32.1 that accompanies this Annual Report on Form 10-K is to be deemed furnished and shall not be deemed “filed” with the SEC and is not to be incorporated by reference into any filing of Assembly Biosciences, Inc. under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, whether made before or after the date of this Annual Report on Form 10-K, irrespective of any general incorporation language contained in such filing.

In accordance with Section 13 or 15(d) of the Securities Exchange Act, the Registrant caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Jason A. Okazaki and John O. Gunderson, jointly and severally, his or her attorneys-in-fact, each with the power of substitution, for him or her in any and all capacities, to sign any amendments to this report, and to file the same, with exhibits thereto and other documents in connection therewith with the Securities and Exchange Commission, hereby ratifying and confirming all that each of said attorneys-in-fact, or his or her substitute or substitutes may do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed by the following persons on behalf of the registrant in the capacities and on the dates indicated.

These financial statements are the responsibility of the Company‘s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company's internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

The critical audit matter communicated below is a matter arising from the current period audit of the financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective or complex judgments. The communication of the critical audit matter does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

The Company’s estimates could be affected by external conditions, including those unique to the Company and general economic conditions. It is reasonably possible these external factors could have an effect on the Company’s estimates and could cause actual results to differ materially from those estimates and assumptions.

Other Risks and Uncertainties

U.S. and global financial markets have experienced volatility and disruption due to macroeconomic and geopolitical events such as rising inflation, changes in interest rates to combat inflation, the war between Russia and Ukraine, the conflicts in the Middle East, the rising tensions between China and Taiwan, as well as tariffs. The Company cannot predict at this time to what extent, if at all, it and its employees, contract research organizations (CROs), vendors and/or collaborators could potentially be negatively impacted by these events.

Cash and Cash Equivalents

All highly liquid investments with original maturities of three months or less at the time of purchase are considered to be cash equivalents. All of the Company’s cash equivalents have liquid markets and high credit ratings.

Investments in Marketable Securities

The Company has designated its investments in marketable securities as available-for-sale and measures these securities at their respective fair values. The Company reviews all available-for-sale securities at each period end to determine if they remain available-for-sale based on their current intent and ability to sell the security if it is required to do so. Marketable securities are classified as short-term or long-term based on the maturity date and their availability to meet current operating requirements. Marketable securities that mature in one year or less from the consolidated balance sheet date are classified as short-term available-for-sale securities, while marketable securities with maturities in one year or beyond one year from the consolidated balance sheet date are classified as long-term.

The Company periodically reviews its marketable securities for declines in fair value below the amortized cost basis to determine whether the impairment, if any, is due to credit-related or other factors. This review includes the credit worthiness of the security issuers, the severity of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not the Company will be required to sell the securities before the recovery of the amortized cost basis. Unrealized gains and losses on available-for-sale securities are reported in other comprehensive loss, and as a component of stockholders' equity until their disposition, with the exception of unrealized losses believed to be related to credit losses which are recognized as an allowance for credit losses on the consolidated balance sheet with the corresponding charge in other income in the period the impairment occurs. Impairment assessments are made at the individual security level each reporting period. The Company elected to exclude accrued interest receivable from the amortized cost basis of its available-for-sale debt securities and to not measure an allowance for credit losses for accrued interest receivable. To date, there have been no credit-related declines in value or other impairments of the Company’s investments in marketable securities. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method.

Leases

All of the Company’s leases are operating leases for facilities and equipment. The Company recognizes a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. The Company determines if an arrangement is or contains a lease at inception or modification of the arrangement. Operating leases with a duration greater than one year are included in operating lease ROU assets, operating lease liabilities - short-term, and operating lease liabilities - long-term in the Company’s consolidated balance sheets. The Company elected the short-term lease exception policy, permitting it to not apply the recognition requirements to leases with terms of less than one year (short-term leases) for all classes of assets. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date. The incremental borrowing rate represents the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease. The Company considers a lease term to be the noncancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend

the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option.

The operating lease ROU assets also include any lease payments made and exclude lease incentives. Lease expense is recognized on a straight-line basis over the expected lease term. Variable lease expenses are recorded when incurred. The Company has elected not to separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component.

Impairment of Long-Lived Assets

The Company monitors the carrying value of long-lived assets, including ROU operating lease assets, for potential impairment and tests the recoverability of such assets whenever events or changes in circumstances indicate the carrying amounts may not be recoverable. If a change in circumstance occurs, the Company performs a test of recoverability by comparing the carrying value of the asset or asset group to its undiscounted expected future cash flows. If cash flows cannot be separately and independently identified for a single asset, the Company will determine whether impairment has occurred for the group of assets for which the Company can identify the projected cash flows. If the carrying values are in excess of undiscounted expected future cash flows, the Company measures any impairment by comparing the fair value of the asset or asset group to its carrying value. There was no impairment of long-lived assets during the years ended December 31, 2024 and 2023.

Fair Value Measurements

The Company follows accounting guidance on fair value measurements for financial instruments measured on a recurring basis, as well as for certain assets and liabilities that are initially recorded at their estimated fair values. Fair value is defined as the exit price, or the amount that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company uses the following three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs to value its financial instruments:

Level 1: Observable inputs such as unadjusted quoted prices in active markets for identical instruments.

Level 2: Quoted prices for similar instruments that are directly or indirectly observable in the marketplace.

Level 3: Significant unobservable inputs which are supported by little or no market activity and that are financial instruments whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment or estimation.

Financial instruments measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement in its entirety requires the Company to make judgments and consider factors specific to the asset or liability. The use of different assumptions and/or estimation methodologies may have a material effect on estimated fair values. Accordingly, the fair value estimates disclosed or initial amounts recorded may not be indicative of the amount the Company or holders of the instruments could realize in a current market exchange.

The carrying amounts of cash equivalents and marketable securities approximate their fair value based upon quoted market prices. Certain of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts which approximate their fair value due to their liquid or short-term nature, such as cash, accounts receivable, accounts payable and accrued expenses.

Revenue Recognition and Accounts Receivable from Collaboration

The Company analyzes its collaboration arrangements to assess whether such arrangements, or transactions between arrangement participants, involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities or are more akin to a vendor-customer relationship. In making this evaluation, the Company considers whether the activities of the collaboration are considered to be distinct and deemed to be within the scope of the collaborative arrangement accounting standard and those that are more reflective of a vendor-customer relationship and, therefore, within the scope of the revenue with contracts with customers accounting standard. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement.

For elements of collaboration arrangements that are not accounted for pursuant to the revenue from contracts with customers accounting standard, an appropriate recognition method is determined and applied consistently, generally by analogy to the revenue from contracts with customers accounting standard. Amounts related to transactions with a counterparty in a collaborative arrangement that is not a customer are presented on a separate line item from revenue recognized from contracts with customers, if any, in the Company’s consolidated statements of operations and comprehensive loss.

Under certain collaborative arrangements, the Company has been reimbursed for a portion of its research and development expenses or participates in the cost-sharing of such research and development expenses. Such reimbursements and cost-sharing arrangements are reflected as a reduction of research and development expense in the Company’s consolidated statements of operations and comprehensive loss.

For arrangements or transactions between arrangement participants determined to be within the scope of the contracts with customers accounting standard, the Company evaluates the term of the arrangement and recognizes revenue when the customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company applies the following five-step model in order to determine this amount: (1) identification of the promised goods or services in the contract; (2) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (3) measurement of the transaction price, including the constraint on variable consideration; (4) allocation of the transaction price to the performance obligations; and (5) recognition of revenue when (or as) the Company satisfies each performance obligation.

The Company has provided standard indemnification and protection of licensed intellectual property for its customers. These provisions are part of assurance the licenses meet the agreements, representations and are not obligations to provide goods or services.

The Company only applies the five-step model to contracts when it is probable the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company must develop assumptions that require judgment to determine the estimated relative SSP of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the SSP of each performance obligation. The Company recognizes the amount of the transaction price that is allocated to the respective performance obligation when the performance obligation is satisfied or as it is satisfied as revenue.

Contract modifications, defined as changes in the scope or price (or both) of a contract that are approved by the parties to the contract, such as a contract amendment, exist when the parties to a contract approve a modification that either creates new, or changes existing, enforceable rights and obligations of the parties to the contract. The Company accounts for contract modifications using one of the following methods depending on facts and circumstances: (i) as a separate contract if the modification adds distinct goods or services and the price reflects the SSP of those additional goods or services; (ii) as a termination of the existing contract and creation of a new contract if the remaining goods or services are distinct from those transferred before the modification; or (iii) as a cumulative catch-up adjustment to the original contract if the remaining goods or services are not distinct from those transferred before the modification.

Licenses

If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, upfront license fees based on the relative value prescribed to the license compared to the total value of the arrangement. The revenue is recognized when the license is transferred to the collaborator and the collaborator is able to use and benefit from the license. For licenses that are not distinct from other obligations identified in the arrangement, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time. If the combined performance obligation is satisfied over time, the Company applies an appropriate method of measuring progress for purposes of recognizing revenue from nonrefundable, upfront license fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Research and Development Services

The promises under the Company’s agreements may include research and development services to be performed by the Company on behalf of the counterparty. If these services are determined to be distinct from the other promises or performance obligations identified in the arrangement, the Company recognizes the transaction price allocated to these

services as revenue over time based on an appropriate measure of progress when the performance by the Company does not create an asset with an alternative use and the Company either has received or has an enforceable right to payment for the performance completed to date. If these services are determined not to be distinct from the other promises or performance obligations identified in the arrangement, the Company recognizes the transaction price allocated to the combined performance obligation as the related performance obligations are satisfied.

Customer Options

If an arrangement contains customer options, the Company evaluates whether the options are material rights because they allow the customer to acquire additional goods or services for free or at a discount. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The identification of a material right, and if identified as a material right, the allocation of the transaction price to it, is based on the SSP, which is determined using assumptions regarding estimated costs, discount rates, post-option development timeline, the probability of technical and regulatory success and the probability the customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised or expires. If the options are deemed not to be a material right, they are considered marketing offers which are excluded as performance obligations at the outset of the arrangement.

Development and Regulatory Milestone Payments

Depending on facts and circumstances, the Company may record revenues from certain milestones in a reporting period before the milestone is achieved if the Company concludes achievement of the milestone is probable and recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. The Company records a corresponding contract asset when this conclusion is reached. Milestone payments that have not been included in the transaction price to date are fully constrained. The Company re-evaluates the probability of achievement of such milestones and any related constraint each reporting period. The Company adjusts its estimate of the overall transaction price, including the amount of collaborative revenue that was recorded, if necessary.

Sales-based Milestone and Royalty Payments

The Company’s customers may be required to pay the Company sales-based milestone payments or royalties on future sales of commercial products. The Company recognizes revenues related to sales-based milestone and royalty payments upon the later to occur of (i) achievement of the collaborator’s underlying sales or (ii) satisfaction of any performance obligation(s) related to these sales, in each case assuming the Company’s licensed intellectual property is deemed to be the predominant item to which the sales-based milestones and/or royalties relate.

The Company receives payments from its customers based on billing schedules established in the contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under the arrangement. If the related performance obligation is expected to be satisfied within the next twelve months, these amounts will be classified in current liabilities. The Company recognizes a contract asset relating to its conditional right to consideration that is not subject to a constraint. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.

A net contract asset or liability is presented for each contract with a customer. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.

There were no accounts receivable from collaboration as of December 31, 2024. At December 31, 2023, all accounts receivable from collaboration are deemed collectible.

Stock-Based Compensation

The Company measures stock-based compensation to employees and board members at fair value on the grant date of the award. The fair value of RSUs is determined based on the number of shares granted and the quoted market price of the Company’s common stock on the date of grant. If stock-based awards are granted in contemplation of or shortly before a planned release of material nonpublic information, and such information is expected to result in a material increase in the Company’s share price, the Company considers whether an adjustment to the observable market price is required when estimating fair values. Compensation cost is recognized as expense on a straight-line basis over the requisite service period of the award. Stock-based awards with graded vesting schedules are recognized using the

accelerated attribution method on a straight-line basis over the requisite service period for each separately vesting portion of the award. For awards that have a performance condition, compensation cost is measured based on the fair value of the award on the grant date, the date performance targets are established, and is expensed over the requisite service period for each separately vesting tranche when achievement of the performance condition becomes probable. The Company assesses the probability of the performance conditions being met on a continuous basis. For awards that have a market condition, compensation cost is measured based on the grant-date fair value of the award and is expensed over the derived service period regardless of whether the underlying market condition is met. Forfeitures are recognized when they occur.

The Company estimates the fair value of stock option grants that do not contain market-based vesting conditions using the Black-Scholes option pricing model. The assumptions used in estimating the fair value of these awards, such as expected term, expected dividend yield, volatility and risk-free interest rate, represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. The Company calculates the weighted average expected term of options using the simplified method where permitted by accounting guidance for stock-based compensation when there is limited history of relevant stock option exercise activity. The Company uses an expected dividend yield of zero as the Company currently does not intend to pay dividends in the foreseeable future. The Company calculates the expected volatility based on the Company’s historical stock prices. The risk-free interest rate assumption is based on the rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the stock option being valued.

The Company is also required to make estimates as to the probability of achieving the specific performance conditions. If actual results are not consistent with the Company’s assumptions and judgments used in making these estimates, the Company may be required to increase or decrease compensation expense, which could be material to the Company’s consolidated results of operations.

Research and Development Expense and Accruals

Research and development costs include personnel-related costs, outside contracted services including clinical study costs, facilities costs, fees paid to consultants, milestone payments prior to FDA approval, license fees prior to FDA approval, professional services, travel costs, dues and subscriptions, depreciation and materials used in clinical trials and research and development and costs incurred under the Company’s collaboration agreements. Research and development costs are expensed as incurred unless there is an alternative future use in other research and development projects. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. Such payments are evaluated for current or long-term classification based on when they will be realized or consumed.

The Company records expenses related to clinical studies and manufacturing development activities based on its estimates of the services received and efforts expended pursuant to contracts with multiple CROs and manufacturing vendors that conduct and manage these activities on its behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical study milestones. In amortizing or accruing service fees, the Company estimates the time period over which services will be performed, enrollment of subjects, number of sites activated and the level of effort expended in each period. If the actual timing of the performance of services or the level of effort varies from the Company’s estimate, the Company will adjust the accrued or prepaid expense balance accordingly. To date, there have been no material differences from the Company’s estimates to the amounts actually incurred.

The Company has entered and may continue to enter into license agreements to access and utilize certain technology. In each case, the Company evaluates if the license agreement results in the acquisition of an asset or a business. To date, none of the Company’s license agreements have been considered to be acquisitions of businesses. For asset acquisitions, the upfront payments to acquire such licenses, as well as any future milestone payments, are immediately recognized as research and development expense when paid, provided there is no alternative future use of the rights in other research and development projects. These license agreements may also include contingent consideration in the form of cash payments to be made for future milestone events. The Company assesses whether such contingent consideration meets the definition of a derivative and to date the Company has determined that such contingent consideration are not derivatives.

Income Taxes

The Company records income taxes using the asset and liability method. Deferred income tax assets and liabilities are recognized for the future tax effects attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases, and operating loss and tax credit carryforwards. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company establishes a valuation allowance if it is more likely than not the deferred tax assets will not be realized based on an evaluation of objective verifiable evidence.

The Company recognizes and measures tax benefits from uncertain tax positions only if it is more likely than not the tax position will be sustained in an audit, including resolution of any related appeals or litigation processes. The tax benefit recognized for a particular tax position is based on the largest amount that is more than 50% likely to be realized upon ultimate settlement. Significant judgment is required to evaluate uncertain tax positions. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals which the Company believes are appropriate. It is the Company’s policy to recognize interest and penalties related to income tax matters in income tax expense.

Pursuant to Section 174 of the Internal Revenue Code (Sec. 174), expenses associated with research conducted in the United States are capitalized and amortized over a five-year period. For expenses associated with research outside of the United States, Sec. 174 expenses are capitalized and amortized over a 15-year period.

Net Loss per Share

Basic net loss per common share excludes dilution and is computed by dividing net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per common share reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity unless inclusion of such shares would be anti-dilutive. Diluted net loss per share is the same as basic net loss per share in the years reported, since the effects of potentially dilutive securities are antidilutive given the net loss for each year presented.

A reconciliation of the numerators and the denominators of the basic and diluted net loss per common share computations is as follows (in thousands, except for share and per share amounts):


	Year Ended December 31,
	2024			2023
Numerator:
Net loss	$	(40,177	)	$	(61,228	)
Denominator:
Weighted average common shares outstanding - basic and diluted		6,004,560			4,577,371
Net loss per share - basic and diluted	$	(6.69	)	$	(13.38	)

Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows:


	December 31,
	2024		2023
Warrants to purchase common stock		814,000		—
Options to purchase common stock		942,193		862,911
Common stock subject to purchase under ESPP		9,386		13,730
Unvested RSUs		68,054		95,182
Total		1,833,633		971,823

Comprehensive Loss

Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on investments in available-for-sale marketable securities. The Company displays comprehensive loss and its components in the consolidated statements of operations and comprehensive loss, net of tax effects if any.

Concentrations of Risk

Credit Risk

Financial instruments which potentially subject the Company to credit risk consist primarily of cash, cash equivalents and marketable securities. The Company holds these investments in highly rated financial institutions, and, by policy, limits the amounts of credit exposure to any one financial institution. These amounts as of and at times during the year ended December 31, 2024 exceeded federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.

Supplier Risk

Certain materials and key components the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a New Drug Application (NDA) filed with the FDA for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from the Company’s suppliers were interrupted for any reason, the Company may be unable to supply any of its product candidates for clinical trials.

Customer Risk

During the year ended December 31, 2024, 100% of the Company's collaboration revenue was recognized from a related party, Gilead, under the Gilead Collaboration Agreement (see Note 8 - Collaboration Agreements). If the collaboration with Gilead does not result in the successful development and commercialization of products or if Gilead terminates the Gilead Collaboration Agreement, the Company may not receive any future payments under the collaboration.

Recently Adopted Accounting Standards

In November 2023, the Financial Accounting Standards Board (the FASB) issued Accounting Standards Update (ASU) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures (ASU 2023-07), which requires public entities to disclose information about their reportable segments’ significant expenses and other segment items on an interim and annual basis. Public entities with a single reportable segment are required to apply the disclosure requirements in ASU 2023-07, as well as all existing segment disclosures and reconciliation requirements in ASC 280 on an interim and annual basis. The Company adopted ASU 2023-07 during the year ended December 31, 2024. See Note 13 - Segment Reporting for further details.

Accounting Pronouncements to Be Adopted

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (ASU 2023-09). The update requires a public business entity to disclose, on an annual basis, a tabular rate reconciliation using both percentages and currency amounts, broken out into specified categories with certain reconciling items further broken out by nature and jurisdiction to the extent those items exceed a specified threshold. In addition, all entities are required to disclose income taxes paid, net of refunds received disaggregated by federal, state/local, and foreign and by jurisdiction if the amount is at least 5% of total income tax payments, net of refunds received. Adoption of ASU 2023-09 allows for either the prospective or retrospective application of the amendment and is effective for annual periods beginning after December 15, 2024, with early adoption permitted. The Company does not expect ASU 2023-09 to have a material impact on the Company’s consolidated financial statements.

In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses (ASU 2024-03), which requires the disaggregation of certain expense captions into specified categories in disclosures within the notes to the

Note 4 - Investments in Marketable Securities

Investments in marketable available-for-sale securities consisted of the following (in thousands):


	December 31, 2024
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Cash equivalents
Money market fund	$	29,066	$	—	$	—		$	29,066
U.S. treasury securities		8,437		—		—			8,437
Total cash equivalents		37,503		—		—			37,503
Short-term marketable securities
U.S. and foreign corporate debt securities		20,971		20		(3	)		20,988
U.S. treasury securities		48,077		40		—			48,117
U.S. and foreign commercial paper		4,625		5		—			4,630
Total short-term marketable securities		73,673		65		(3	)		73,735
Total cash equivalents and marketable securities	$	111,176	$	65	$	(3	)	$	111,238


	December 31, 2023
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Cash equivalents
Money market fund	$	18,982	$	—	$	—		$	18,982
Total cash equivalents		18,982		—		—			18,982
Short-term marketable securities
U.S. and foreign corporate debt securities		17,595		41		(3	)		17,633
U.S. treasury securities		76,891		127		—			77,018
U.S. and foreign commercial paper		15,728		27		—			15,755
Total short-term marketable securities		110,214		195		(3	)		110,406
Total cash equivalents and marketable securities	$	129,196	$	195	$	(3	)	$	129,388

Short-term marketable securities held as of December 31, 2024 and 2023 had contractual maturities of less than one year.

There were no realized gains and losses for the years ended December 31, 2024 and 2023. As of December 31, 2024, investments which were in an unrealized loss position were not material and generally due to interest rate fluctuations, as opposed to declines in credit quality. The Company determined it has the intent and ability to hold all marketable securities that have been in a continuous loss position until recovery of their amortized cost basis, which may be until maturity. As a result, the Company did not recognize any credit losses related to its investments and all unrealized gains and losses on available-for-sale securities are recorded in accumulated other comprehensive loss on the consolidated balance sheets during the years ended December 31, 2024 and 2023.

Accrued interest receivable was $0.4 million and $0.3 million as of December 31, 2024 and 2023, respectively, and was recorded in prepaid expenses and other current assets on the consolidated balance sheets. The Company did not write off any accrued interest receivable during the years ended December 31, 2024 and 2023.

Fair Value Measurement

The following tables presents the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):


	December 31, 2024
	Level 1		Level 2		Level 3		Fair Value
Cash equivalents
Money market fund	$	29,066	$	—	$	—	$	29,066
U.S. treasury securities		—		8,437		—		8,437
Total cash equivalents		29,066		8,437		—		37,503
Short-term marketable securities
U.S. and foreign corporate debt securities		—		20,988		—		20,988
U.S. treasury securities		—		48,117		—		48,117
U.S. and foreign commercial paper		—		4,630		—		4,630
Total short-term marketable securities		—		73,735		—		73,735
Total assets measured at fair value	$	29,066	$	82,172	$	—	$	111,238


	December 31, 2023
	Level 1		Level 2		Level 3		Fair Value
Cash equivalents
Money market fund	$	18,982	$	—	$	—	$	18,982
Total cash equivalents		18,982		—		—		18,982
Short-term marketable securities
U.S. and foreign corporate debt securities		—		17,633		—		17,633
U.S. treasury securities		—		77,018		—		77,018
U.S. and foreign commercial paper		—		15,755		—		15,755
Total short-term marketable securities		—		110,406		—		110,406
Total assets measured at fair value	$	18,982	$	110,406	$	—	$	129,388

Money market funds are highly liquid and actively traded marketable securities that generally transact at a stable $1.00 net asset value representing its estimated fair value. The Company estimates the fair value of its U.S. and foreign corporate debt securities, U.S. treasury securities and U.S. and foreign commercial paper by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs.

There were no transfers between Level 1, Level 2 or Level 3 for any of the years presented.

Reverse Stock Split

In September 2023, the Company received a letter from the Listing Qualifications Department of the Nasdaq Stock Market notifying the Company, as the bid price for its common stock had closed below $1.00 per share for the last 30 consecutive business days, it was not in compliance with Nasdaq Listing Rule 5450(a)(1), which is the minimum bid price requirement for continued listing on the Nasdaq Global Select Market. In accordance with Nasdaq Listing Rule 5810(c)(3)(A), the Company was provided a 180-calendar day period, or until March 25, 2024, to regain compliance with the minimum bid price requirement. The continued listing standard would be met once the closing bid price of the Company’s common stock was at least $1.00 per share for a minimum of ten consecutive business days during the 180-calendar day period. In January 2024, the Company's stockholders approved a reverse stock split of its common stock at a range of ratios between 1-for-7 to 1-for-17, and the Company's board of directors approved the implementation of the reverse stock split at a ratio of 1-for-12 (the Reverse Stock Split). The Reverse Stock Split was effective as of February 9, 2024 and the Company regained compliance with the minimum bid price requirement in February 2024.

As of the effective time of the Reverse Stock Split, every 12 issued and outstanding shares of the Company’s common stock was automatically reclassified into one issued and outstanding share of the Company’s common stock. This reduced the number of shares outstanding from 65.8 million shares to 5.5 million shares. The Reverse Stock Split did not affect the number of authorized shares of common stock or the par value of the common stock. No fractional shares of common stock were issued in connection with the Reverse Stock Split and all fractional shares were rounded down to the nearest whole share with respect to outstanding shares of common stock. Any holders of common stock who would have otherwise received a fractional share of common stock pursuant to the Reverse Stock Split, received cash in lieu of the fractional share. All share and per share amounts of the Company's common stock presented in this Annual Report on Form 10-K have been adjusted to reflect the 1-for-12 Reverse Stock Split. The Company's authorized shares of common stock remain at 150,000,000 and its authorized shares of preferred stock remain at 5,000,000.

Sale of Common Stock and Warrants

At-The-Market Offering

In August 2020, the Company entered into a sales agreement under which the Company may offer and sell shares of its common stock having an aggregate offering price of up to $100.0 million through “at-the-market” offerings (2020 ATM), pursuant to its shelf registration statement on Form S-3 with the SEC (File No. 333-248469), which became effective in September 2020. The Company did not sell any shares of its common stock under the 2020 ATM during the year ended December 31, 2024. During the year ended December 31, 2023, the Company issued and sold 261,170 shares of its common stock under the 2020 ATM, for which the Company received net proceeds of $4.5 million, after deducting commissions, fees and expenses.

In November 2024, the Company terminated the 2020 ATM and entered into a new sales agreement under which the Company may offer and sell shares of its common stock having an aggregate offering price of up to $75.0 million through "at-the-market" offerings (2024 ATM), pursuant to its shelf registration statement on Form S-3 (File No. 333-270760), which became effective in April 2023. During the year ended December 31, 2024, the Company issued and sold 152,666 shares of its common stock under the 2024 ATM, for which the Company received net proceeds of $2.0 million, after deducting commissions, fees and expenses.

Registered Direct Offering

In June 2024, under the June 2024 Registered Direct Offering and pursuant to its shelf registration statement on Form S-3 on file with the SEC, the Company issued and sold 634,500 shares of common stock and a warrant to purchase up to 634,500 shares of common stock. The common stock and warrant were sold at a combined offering price of $15.46 per share for aggregate gross proceeds to the Company of $9.8 million.

Private Placements

In October 2023, the Company entered into the Gilead Equity Agreements, which were amended in June 2024. Pursuant to the Gilead Equity Agreements, Gilead purchased 1,089,472 shares of the Company’s common stock in a private placement at a purchase price of $13.92 per share for total proceeds of $15.2 million. Of these proceeds, $5.9 million was determined to be a premium on the purchase of the Company’s common stock and allocated to the single

combined performance obligation under the Gilead Collaboration Agreement (see Note 8 - Collaboration Agreements). The fair value of Gilead's common stock purchase was $9.3 million and total proceeds from the issuance of the Company's common stock under the Gilead Equity Agreements was $9.1 million, net of $0.2 million in issuance costs. Pursuant to the terms of the amended Gilead Equity Agreements, if the Company completed an equity financing by October 2024, which would have resulted in at least $30.0 million of proceeds to the Company, then, subject to approval by the Company’s stockholders (which was obtained on January 31, 2024), the Company would have had the right to require Gilead to purchase additional shares of its common stock from the Company in an amount that resulted in Gilead owning 29.9% of the Company’s common stock. This right expired in October 2024. The terms of the Gilead Equity Agreements also provided Gilead with the right to elect to purchase additional shares of common stock from the Company at a premium in an amount that would result in Gilead owning 29.9% of the Company's common stock. The Gilead Equity Agreements also include a three-year standstill provision and a two-year lockup provision, each with customary exceptions, and provide Gilead with certain other stock purchase rights and registration rights, as well as the right to designate two directors to the Company’s board of directors.

In June 2024, the Company issued and sold 179,500 shares of common stock and a warrant to purchase up to 179,500 shares of common stock under the June 2024 Private Placement with Gilead. This transaction was executed concurrently with the June 2024 Registered Direct Offering pursuant to anti-dilution provisions in the Investor Rights Agreement, with the common stock and warrant sold at the same combined offering price of $15.46 per share for aggregate gross proceeds to the Company of $2.8 million.

In December 2024, Gilead exercised its right under the Gilead Equity Agreements to purchase an additional 940,499 shares of common stock from the Company at a purchase price of $21.37 per share, which represents a 35% premium to the 30 trading day volume weighted average price immediately prior to the date of purchase. The Company received aggregate proceeds of $20.1 million, of which $5.2 million was determined to be a premium on the purchase of the Company’s common stock and allocated to the single combined performance obligation under the Gilead Collaboration Agreement (see Note 8 - Collaboration Agreements). The fair value of Gilead's common stock purchase was $14.9 million.

Warrants

The warrants sold in the June 2024 Registered Direct Offering and June 2024 Private Placement have an exercise price of $17.00 per share, were immediately exercisable upon issuance, and expire on June 18, 2029. Neither party may exercise any portion of the warrants to the extent it would beneficially own more than the limits defined in the warrant agreements. The exercise price and number of shares of the Company's common stock issuable upon the exercise of the warrants are subject to adjustment in the event of any stock dividends and distributions, stock splits, stock combinations or stock reclassifications, as described in the respective warrant agreements. Under certain circumstances, the warrants may be exercised on a “cashless” basis.

The warrants were classified as a component of permanent stockholders’ equity within additional paid-in-capital and were recorded at the issuance date. The warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, permit the holders to receive a fixed number of common shares upon exercise, are indexed to the Company’s common stock and meet the equity classification criteria. In addition, such warrants do not provide any guarantee of value or return.

As of December 31, 2024, there were 814,000 outstanding and no warrants exercised during the year then ended.

As of December 31, 2024, the Company had awards outstanding under the following shareholder approved plans: 2010 Equity Incentive Plan (the 2010 Plan), which has been frozen; the Assembly Biosciences, Inc. Amended and Restated 2014 Stock Incentive Plan (the 2014 Plan); and the 2018 Plan. Shares of common stock underlying awards that are forfeited under the 2010 Plan on or after June 2, 2016 will become available for issuance under the 2014 Plan. As of December 31, 2024, the Company also had awards outstanding under the Assembly Biosciences, Inc. 2017 Inducement Award Plan, the Assembly Biosciences, Inc. 2019 Inducement Award Plan, and the Assembly Biosciences, Inc. 2020 Inducement Award Plan.

The Company issues new shares of common stock to settle options exercised or vested RSUs. The Company also issues new shares of common stock in connection with purchases of shares of common stock by eligible employees under the Assembly Biosciences, Inc. Second Amended and Restated Employee Stock Purchase Plan (the 2018 ESPP).

In February 2024, the Reverse Stock Split became effective. All outstanding stock options and restricted stock units presented have been adjusted to reflect the 1-for-12 Reverse Stock Split.

Stock Plan Activity

Stock Options

The following table summarizes the stock option activity and related information for 2024:


	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (Years)		Total Intrinsic Value (in thousands)
Outstanding as of December 31, 2023		862,911		$	69.00		6.7	$	1
Granted		220,165			13.56
Exercised		(514	)		10.68
Forfeited		(37,685	)		127.88
Expired		(102,684	)		63.79
Outstanding as of December 31, 2024		942,193		$	54.24		7.3	$	1,383
Options vested and exercisable as of December 31, 2024		517,237		$	85.60		6.2	$	375
Options expected to vest as of December 31, 2024		942,193		$	54.24		7.3	$	1,383

The weighted-average grant-date fair value of options granted was $10.04 and $7.68 during the years ended December 31, 2024 and 2023, respectively. The intrinsic value of options exercised was not material during the year ended December 31, 2024. There were no options exercised in 2023.

RSUs

The following table summarizes RSU activity and related information for 2024:


	Number of RSUs			Weighted Average Fair Value Per RSU at Grant Price
Nonvested as of December 31, 2023		95,182		$	32.64
Granted		25,353			13.35
Vested		(51,872	)		41.64
Forfeited		(609	)		25.39
Nonvested as of December 31, 2024		68,054		$	18.66

The total fair value of RSUs vested and settled during 2024 and 2023 was $2.2 million and $2.8 million, respectively. The total intrinsic value of RSUs vested and settled during 2024 and 2023 was $0.7 million and $0.5 million, respectively.

In July 2021, the Company granted 26,981 RSUs with performance-based vesting conditions upon the achievement of clinical milestones to the majority of employees, including executive officers. The awards had a grant date fair value of $1.2 million and vested upon achievement of performance conditions fully met by December 31, 2023. The Company did not recognize any stock-based compensation expense for these RSUs during the year ended December 31, 2024, compared to $0.3 million during the year ended December 31, 2023. All awards were fully vested with no remaining unrecognized compensation cost as of December 31, 2023.

In March 2022, the Company granted 21,248 RSUs with market-based vesting conditions to members of management, including its executive officers. The awards had a grant date fair value of $0.4 million and were recognized over the derived service period of 1.5 years and vest upon the achievement of certain market-based conditions which have not been achieved as of December 31, 2024. The Company did not recognize any stock-based compensation expense for these RSUs during the year ended December 31, 2024, compared to $0.1 million for these RSUs during the year ended December 31, 2023.

In August 2022, the Company granted 43,748 RSUs with performance-based vesting conditions upon the achievement of clinical milestones to its executive officers. The awards had a grant date fair value of $1.1 million and vested upon achievement of performance conditions fully met by December 31, 2024. The Company recognized stock-based compensation expense of $0.1 million and $0.6 million for these RSUs during the years ended December 31, 2024 and 2023, respectively. All awards were fully vested with no unrecognized compensation cost as of December 31, 2024.

Employee Stock Purchase Plan

In May 2024, the Company's stockholders approved an amendment to the 2018 ESPP, which increased the aggregate number of shares of common stock available for purchase by employees up to an aggregate of 226,398 shares at a discount to the market price. Eligible employees may participate through payroll deductions of up to 15% of such employee’s compensation for each pay period subject to annual statutory limits.

Eligible employees can purchase the Company’s common stock at the end of a predetermined offering period at 85% of the lower of the fair market value at the beginning or end of the offering period. Under the 2018 ESPP, the offering periods end on the last business day occurring on or before May 14 or November 14. The ESPP is compensatory and results in stock-based compensation expense.

In May and November 2024, employees purchased 7,252 and 7,685 shares of common stock, respectively, under the 2018 ESPP. In May and November 2023, employees purchased 7,534 and 6,919 shares of common stock, respectively, under the 2018 ESPP. As of December 31, 2024, 156,815 shares of common stock are available for future sale under the Company’s 2018 ESPP. Stock-based compensation expense recorded in connection with the 2018 ESPP was $0.1 million for both the years ended December 31, 2024 and 2023.

Valuation Assumptions

A summary of the assumptions used to estimate the fair values of stock options grants for the years presented is as follows:


	Year Ended December 31,
	2024	2023
Exercise price	$12.90 - $16.75	$8.64 - $18.36
Expected volatility	79.1% - 86.9%	77.5% - 87.1%
Risk-free rate	3.50% - 4.57%	3.59% - 4.49%
Expected term (years)	5.5 - 7.5	5.5 - 7.5
Expected dividend yield	0%	0%

The fair value of ESPP purchase rights and stock appreciation rights were not material for any period presented.

Note 8 - Collaboration Agreements

The following table summarizes the collaboration revenue recognized from the Company's collaboration agreements in the consolidated statement of operations and comprehensive loss for the years presented (in thousands):


	Year Ended December 31,
	2024		2023
Gilead (a related party)	$	28,520	$	4,430
BeiGene, Ltd. (BeiGene)		—		2,733
Total collaboration revenue	$	28,520	$	7,163

The following tables present changes in the Company’s contract liabilities (in thousands):


	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Year Ended December 31, 2024
Contract liabilities:
Deferred revenue	$	86,294	$	15,226	$	(28,520	)	$	73,000

	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Year Ended December 31, 2023
Contract liabilities:
Deferred revenue	$	2,733	$	90,724	$	(7,163	)	$	86,294


	Year Ended December 31,
	2024		2023
Collaboration revenue recognized in the period from
Amounts included in deferred revenue at the beginning of the period	$	28,271	$	2,733
Performance obligations satisfied in previous period	$	—	$	—

Gilead Agreement

In October 2023, the Company entered into the Gilead Collaboration Agreement and the Gilead Equity Agreements under which it received total proceeds of $100.0 million. Under the Gilead Collaboration Agreement, Gilead exclusively licensed to the Company its HPI program and NNPI program, while retaining opt-in rights to these programs and has an option to take an exclusive license, on a program-by-program basis, to all of the Company’s other current and future pipeline programs. During the 12-year collaboration term (subject to payment of certain extension fees) and for a specified period thereafter, Gilead may exercise its opt-in rights, on a program-by-program basis, at one of two timepoints—completion of a certain Phase 1 study or completion of a certain Phase 2 study for

the first product within the program—upon payment of an opt-in fee ranging from $45.0 million to $125.0 million per program depending on the type of program and when the option is exercised.

In December 2024, the Company and Gilead entered into the First Amendment to the Gilead Collaboration Agreement, which restructured the timing of specific options exercisable in the agreement and the fees payable to the Company to support an accelerated development plan for 6250. To facilitate this development plan, the Company received a non-refundable payment of $10.0 million from Gilead and the opt-in fee payable by Gilead in connection with 6250 was restructured, though it remains in the range of opt-in fees detailed above. The $10.0 million payment received in connection with the First Amendment to the Gilead Collaboration Agreement is creditable towards future collaboration-related payments payable by Gilead.

If Gilead exercises its opt-in right to any current or future program under the collaboration, the Company is eligible to receive up to $330.0 million in potential regulatory and commercial milestones on that program, in addition to royalties ranging from the high single-digits to high teens, depending on the clinical stage of the program at the time of the opt-in. Following Gilead’s exercise of its option for each program, the Company may opt in to cover 40% of the research and development costs in the United States and share 40% of the profits and operating loss in the United States for products within the program in lieu of receiving milestones and royalties for that program in the United States, unless the Company later opts out of the cost/profit share for the program. Prior to Gilead’s potential exercise of its opt-in, the Company will be primarily responsible for all discovery, research and development on its programs and the two Gilead-contributed programs. Following Gilead’s opt-in, Gilead will control the further discovery, research, development, and commercialization on any optioned programs. During the term, Gilead will continue to support the collaboration through extension fees of $75.0 million in each of the third, fifth and seventh years of the collaboration.

The Gilead Collaboration Agreement is subject to termination by either party for the other party’s uncured, material breach or insolvency. Subject to certain limitations, the Company and Gilead both have certain termination for convenience rights, upon sufficient prior written notice, with respect to programs that one party in-licenses from the other (subject to Gilead’s option rights), and with respect to Gilead, for programs it has option rights to (subject to certain time limitations with respect to existing Company programs). Gilead also has a right to terminate the collaborative activities under the Gilead Collaboration Agreement at certain specified points during the collaboration term. Other customary termination rights are further provided in the Gilead Collaboration Agreement.

At the commencement of the arrangement, the Company concluded Gilead was a customer and accordingly, the Gilead Collaboration Agreement was within the scope of the revenue from contracts with customers guidance. The Company initially identified a single combined performance obligation for the discovery, research and development services (the R&D Services) consisting of a series of distinct services that are substantially the same and have the same pattern of transfer. The Company concluded the R&D Services were distinct from Gilead's right to obtain an exclusive license to any of the Company's programs as Gilead benefits from the knowledge and expertise gained from the R&D Services and the Company's know-how is not highly specialized in nature. Gilead could perform the R&D Services themselves, particularly considering Gilead contributed its HPI and NNPI programs and Gilead may continue to conduct development activities on programs being developed under the Gilead Collaboration Agreement. None of the options in the contract were deemed to be separate performance obligations as the options did not provide any discounts or other rights which would be considered a material right in the arrangement.

The Company determined the Gilead Collaboration Agreement and Gilead Equity Agreements should be assessed as a single combined transaction because the agreements were negotiated and entered into together, with a single commercial objective. The Company accounted for the agreements based on the fair values of the assets and services exchanged. Of the $15.2 million in proceeds received under the Gilead Equity Agreements in October 2023, $5.9 million was determined to be a premium on the purchase of the Company’s common stock and allocated to the single combined performance obligation under the Gilead Collaboration Agreement. The value the Company received from the licenses Gilead contributed were not material within the context of the contract and accordingly, the Company made no adjustments to the transaction price for them at the commencement of the arrangement. In December 2024, Gilead exercised its right under the Gilead Equity Agreements to purchase additional shares of the Company's common stock for aggregate proceeds of $20.1 million, of which $5.2 million was determined to be a premium on the purchase of the Company’s common stock and allocated to the single combined performance obligation under the Gilead Collaboration Agreement.

The Company determined the First Amendment to the Gilead Collaboration Agreement represents a contract modification within the scope of the revenue from contracts with customers guidance. The Company concluded there continues to be a single combined performance obligation consisting of a series of distinct R&D Services, and therefore, the remaining services under the First Amendment to the Gilead Collaboration Agreement are distinct from the R&D Services already provided. Accordingly, the Company accounted for the First Amendment to the Gilead Collaboration Agreement as a termination of the existing contract and the creation of a new contract and is recognizing the revenue prospectively by reassessing the transaction price and allocating it to the remaining R&D Services.

The amended transaction price as a result of the modification was determined to be $74.2 million, consisting of the unrecognized portion of the transaction price under the original contract, the premium of $5.2 million on Gilead's purchase of the Company's common stock in December 2024 and $10.0 million received from Gilead pursuant to the First Amendment to the Gilead Collaboration Agreement.

The variable consideration related to the regulatory and commercial milestones has not been included in the transaction price as of December 31, 2024, since Gilead has not opted in to take a license to any of the Company's programs. Any variable consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur pursuant to the Gilead Collaboration Agreement. The Company will reevaluate the transaction price in each reporting period as uncertain events are resolved or other changes in circumstances occur.

The transaction price is reflected as collaboration revenue when realized in the Company’s consolidated statements of operations. The Company recognizes revenue over time using a cost-based input method, based on internal and external labor cost effort to perform the services, over the initial non-cancellable term of three years since this method best reflects the transfer of services to Gilead. In applying a cost-based input method of revenue recognition, the Company uses actual costs incurred relative to estimated total costs to fulfill each performance obligation. A cost-based input method of revenue recognition requires the Company to make estimates of costs to complete the performance obligation. The cumulative effect of any revisions to estimated costs to complete the performance obligation and associated variable consideration will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods.

The Company recognized $28.5 million and $4.4 million of collaboration revenue under the Gilead Collaboration Agreement during the years ended December 31, 2024 and 2023, respectively. The transaction price for future collaborative activities was recorded as deferred revenue on the consolidated balance sheet as of December 31, 2024, of which $37.6 million was included in deferred revenue - short-term and $35.4 million was included in deferred revenue - long-term. During the year ended December 31, 2024, the Company incurred $0.3 million in reimbursable expenses due to Gilead. During the year ended December 31, 2023, the Company did not incur any reimbursable expenses due to Gilead.

Arbutus Biopharma Agreement

In August 2020, the Company and Arbutus Biopharma Corporation (Arbutus Biopharma) entered into a Clinical Trial Collaboration Agreement (the Arbutus Biopharma Agreement) to conduct a randomized, multi-center, open-label Phase 2 clinical trial to explore the safety, pharmacokinetics and antiviral activity of the triple combination of vebicorvir (VBR), AB-729 and a nucleos(t)ide analog reverse transcriptase inhibitor (NrtI) compared to the double combinations of VBR with a NrtI and AB-729 with a NrtI. Under the Arbutus Biopharma Agreement, Assembly and Arbutus Biopharma shared responsibility for the costs of the trial equally, excluding manufacturing supply which were the burden of each company to supply their respective drugs, VBR and AB-729. Assembly was responsible for conducting this clinical trial with Arbutus Biopharma reimbursing Assembly its share of expenses. In February 2023, Assembly and Arbutus Biopharma terminated the Phase 2 clinical trial early, at the end of the 48-week on-treatment period.

The Arbutus Biopharma Agreement was within the scope of the collaborative arrangements guidance as both parties were active participants and were exposed to significant risks and rewards dependent on the success of the collaborative activity. Reimbursements and cost-sharing portions from Arbutus Biopharma were reflected as a reduction of research and development expense when realized in the Company’s consolidated statements of operations. During the year ended December 31, 2024, the Company recognized research and development expenses of $0.3 million for net amounts refundable to Arbutus Biopharma after the final reconciliation of clinical trial costs.

Note 10 - Income Taxes

Income tax expense is as follows (in thousands):


	December 31,
	2024		2023
Current:
Federal	$	—	$	33
State		330		—
Foreign		—		—
		330		33
Deferred:
Federal		—		—
State		—		—
Foreign		—		—
		—		—
Income tax expense	$	330	$	33

The effective tax rate of the Company's provision for income taxes differs from the federal statutory rate as follows:


	As of December 31,
	2024			2023
Statutory federal income tax rate		21.0	%		21.0	%
State taxes, net of federal tax benefit		8.1			7.7
Research and development tax credits		8.4			4.4
Return to provision adjustments		(4.8	)		0.3
Uncertain tax positions		(1.7	)		(0.9	)
Stock-based compensation		(8.4	)		(1.7	)
Other		(0.5	)		(0.5	)
Change in valuation allowance		(22.9	)		(30.4	)
Income taxes provision (benefit)		-0.8	%		-0.1	%

Significant components of the Company’s deferred taxes are as follows (in thousands):


	As of December 31,
	2024			2023
Deferred tax assets:
Federal and state-operating loss carryforwards	$	131,994		$	148,119
Stock-based compensation		7,078			9,948
Capitalized research expense		35,593			28,578
Deferred revenue		18,484			—
Operating lease liabilities		782			594
Research and development credits		18,436			15,816
Other		53			19
Total deferred tax assets		212,420			203,074
Valuation allowance		(211,614	)		(202,428	)
Deferred tax asset, net of valuation allowance	$	806		$	646

Deferred tax liabilities:
Operating lease right-of-use assets	$	(777	)	$	(593	)
Other		(29	)		(53	)
Total deferred tax liabilities		(806	)		(646	)
Net deferred tax liability	$	—		$	—

The Company maintains a valuation allowance on deferred tax assets due to the uncertainty regarding the ability to utilize these deferred tax assets in the future. The valuation allowance increased by $9.2 million and $18.4 million for the years ended December 31, 2024 and 2023, respectively, primarily due to an increase in the Company’s federal and state-operating loss carryforwards.

Net operating loss and tax credit carryforwards as of December 31, 2024 are as follows (in thousands):


	Amount		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	391,182	Indefinite
Net operating losses, federal (pre January 1, 2018)		67,208	2029 - 2037
Net operating loss, state (Indefinite)		—	Indefinite
Net operating loss, state (Definite)		561,968	2029 - 2044
Research and development tax credits, federal		17,820	2028 - 2044
Research and development tax credits, state		6,783	Indefinite

Pursuant to Internal Revenue Code (IRC), Sections 382 and 383, use of the Company’s U.S. federal and state net operating loss and research and development income tax credit carryforwards may be limited in the event of a cumulative change in ownership of more than 50.0% within a three-year period. The Company has performed an ownership change study through December 31, 2024 and has determined a “change in ownership” as defined by IRC Section 382 and the rules and regulations promulgated thereunder, did occur in December 2010, January 2013 and October 2014. The Company has adjusted its net operating loss carryovers to appropriately reflect any attributes which will expire due to the limitation. If further changes in ownership occur, additional net operating loss and tax credit carryforwards could be eliminated or restricted. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance.

The following table summarizes activity related to the Company’s gross unrecognized tax benefits (in thousands):


	As of December 31,
	2024			2023
Balances as of beginning of year	$	4,495		$	3,873
Increases related to prior year tax positions		—			47
Decreases related to prior year tax positions		(31	)		—
Increases related to current year tax positions		711			575
Balances as of end of year	$	5,175		$	4,495

The unrecognized tax benefits, if recognized, would not have an impact on the Company’s effective tax rate assuming the Company continues to maintain a full valuation allowance position. Based on the prior year’s operations and experience, the Company does not expect a significant change to its unrecognized tax benefits over the next twelve months. The unrecognized tax benefits may increase or change during the next year for unexpected or unusual items that arise in the ordinary course of business. In subsequent periods, any interest and penalties related to uncertain tax positions will be recognized as a component of income tax expense.

The Company files income tax returns in the U.S. federal, California and other state and foreign jurisdictions and is not currently under examination by federal, state, or local taxing authorities for any open tax years. Due to net operating loss carryforwards, all years effectively remain open for income tax examination by tax authorities in the U.S. and states in which the Company files tax returns.

Note 11 - Leases

Operating Leases

In August 2023, the Company entered into a sublease agreement for office and laboratory space in South San Francisco, California to serve as the Company's corporate headquarters. The sublease originally expired in October 2025, with an option to extend through September 2029. In December 2024, the Company amended the sublease to extend the term through September 2029 and modify the base rent payments beginning in January 2025, with scheduled annual rent increases over the remaining lease term. The Company's previous corporate headquarters sub-sublease in South San Francisco, California expired in December 2023. The Company also leased office space in Carmel, Indiana under a lease agreement that expired in August 2023, which had been substantially subleased since February 2021. The Company dissolved its China subsidiary in 2024, allowing the lease for its registrational office in Shanghai to expire in March 2024. The lease for the Company's registrational office in Beijing, which was month-to-month, ended in 2023. The Company also leases certain laboratory equipment accounted for as operating leases expiring at various dates, with the final lease expiring in 2025.

When the Company cannot determine the implicit rate in its leasing arrangements, the Company uses its incremental borrowing rate as the discount rate when measuring operating lease liabilities. The incremental borrowing rate represents an estimate of the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease within a particular currency environment.

At December 31, 2024, the Company had operating lease liabilities of $3.1 million and ROU assets of $3.1 million.

The following summarizes quantitative information about the Company’s operating leases (in thousands):


	Year Ended December 31,
	2024		2023
Lease cost
Operating lease cost	$	1,417	$	3,507
Short-term lease cost		1		12
Variable lease cost		727		1,504
Sublease income		—		(102	)
Total lease cost, net	$	2,145	$	4,921

As of December 31, 2024, the weighted-average remaining lease term for operating leases was 4.7 years and the weighted-average discount rate for operating leases was 10.0%.

As of December 31, 2024, the maturities of the Company’s operating lease liabilities were as follows (in thousands):


2025	$	751
2026		806
2027		834
2028		863
2029		671
Total		3,925
Less: present value discount		(836	)
Operating lease liabilities	$	3,089

Note 13 - Segment Reporting

The Company operates as a single operating segment focusing on developing innovative therapeutics targeting serious viral diseases. The Company's chief operating decision maker (CODM) is its Chief Executive Officer and President, who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources.

The measure of segment profit or loss used by the CODM to evaluate performance and allocate resources is consolidated net loss as reported in the Company's consolidated statements of operations. This measure is used by the CODM to assess its cash runway and make strategic decisions about resource allocation. The CODM does not use asset measures to evaluate segment performance or make resource allocation decisions.

Operating expenses include all costs necessary to operate the Company's business, primarily consisting of research and development and general and administrative expenses directly related to advancing the Company's programs. These expenses are reviewed by the CODM on a consolidated basis as part of evaluating the Company's overall financial performance. During the years ended December 31, 2024 and 2023, the Company generated all of its collaboration revenue from two customers, one of which is a related party (see Notes 3 - Related Party and 8 - Collaboration Agreements). For the years ended December 31, 2024 and 2023, all of the Company's revenue and long-lived assets were in the United States.

The following table presents the significant segment expenses and other segment items regularly reviewed by the Company's CODM:


	Years Ended December 31,
	2024				2023
Collaboration revenue ($28,520 and $4,430 from a related party)	$	28,520			$	7,163
Less:
External program expenses:
Research and discovery		8,985				9,741
ABI-6250		6,396				421
ABI-5366		6,215				2,869
ABI-1179		4,239				—
ABI-4334		2,646				1,947
Vebicorvir		(43	)	(1)		1,755
ABI-H3733		—				3,383
ABI-H2158		—				226
Total external program expenses		28,438				20,342
Employee and contractor-related expenses (2)		23,819				22,956
Facility and other expenses		3,676				5,602
Total research and development		55,933				48,900
General and administrative (2)		18,007				22,909
Other segment items (3)		(5,243	)			(3,418	)
Net loss	$	(40,177	)		$	(61,228	)

(1)

Reflects net amounts refundable to the Company after the final reconciliation of costs of the clinical trial conducted pursuant to the Arbutus Biopharma Agreement, which was terminated in February 2023.

(2)

Includes stock-based compensation expense, see Note 7 - Stock-Based Compensation for further details.

(3)

Other segment items include interest and other income, net, and income tax expense as reported in the Company's consolidated statements of operations and comprehensive loss.


Title of Each Class	Trading Symbol(s)	Name of Exchange on which Registered
Common Stock, $0.001 Par Value	ASMB	The Nasdaq Global Select Market


		Page
PART I
Item 1.	Business	1
Item 1A.	Risk Factors	20
Item 1B.	Unresolved Staff Comments	33
Item 1C.	Cybersecurity	33
Item 2.	Properties	34
Item 3.	Legal Proceedings	34
Item 4.	Mine Safety Disclosures	34
PART II
Item 5.	Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities	35
Item 6.	[Reserved]	35
Item 7.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	36
Item 7A.	Quantitative and Qualitative Disclosures about Market Risk	48
Item 8.	Financial Statements and Supplementary Data	48
Item 9.	Changes in and Disagreements with Accountants on Accounting and Financial Disclosure	48
Item 9A.	Controls and Procedures	48
Item 9B.	Other Information	48
Item 9C.	Disclosure Regarding Foreign Jurisdictions that Prevent Inspections	48
PART III
Item 10.	Directors, Executive Officers and Corporate Governance	49
Item 11.	Executive Compensation	49
Item 12.	Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters	49
Item 13.	Certain Relationships and Related Transactions, and Director Independence	50
Item 14.	Principal Accountant Fees and Services	50
Item 15.	Exhibits, Financial Statement Schedules	51
Item 16.	Form 10-K Summary	53
Financial Statements		F-1


	Year Ended December 31,				$ Change		% Change
	2024		2023		2024 vs. 2023		2024 vs. 2023
Interest and other income, net	$	5,573	$	3,451	$	2,122		61	%


	Year Ended December 31,
	2024			2023
Net cash (used in) provided by operating activities	$	(51,117	)	$	22,743
Net cash provided by (used in) investing activities		40,171			(69,138	)
Net cash provided by financing activities		29,449			13,818
Net increase (decrease) in cash and cash equivalents	$	18,503		$	(32,577	)


Plan Category	Number of securities to be issued upon exercise of outstanding options, warrants and rights (a)			Weighted average exercise price of outstanding options, warrants and rights(1) (b)		Number of securities remaining available for future issuance under equity compensation plans (excluding securities reflected in column (a)) (c)
Equity compensation plans approved by security holders		858,550	(2)	$	39.95		484,852	(3)

Equity compensation plans not approved by security holders		965,697	(4)	$	34.54		13,761	(5)
Total		1,824,247					498,613


☒	ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934


☐	TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934


Large accelerated filer	☐	Accelerated filer	☐

Non-accelerated filer	☒	Smaller reporting company	☒

		Emerging growth company	☐


Exhibit Number	Description of Document	Registrant’s Form	Dated	Exhibit No.	Filed Herewith
3.1	Sixth Amended and Restated Certificate of Incorporation dated May 25, 2022.	10-K	03/28/2024	3.1
3.2	Certificate of Amendment to Sixth Amended and Restated Certificate of Incorporation of Assembly Biosciences, Inc., dated February 9, 2024.	8-K	02/13/2024	3.1
3.3	Amended and Restated Bylaws as amended through December 12, 2024.	8-K	12/13/2024	3.1
4.1	Specimen of Common Stock Certificate.				X
4.2	Description of Securities.	10-K	03/28/2024	4.2
4.3	Registered Warrant.	8-K	06/18/2024	4.1
4.4	Private Placement Warrant.	8-K	06/18/2024	4.2
10.1	Sublease, dated July 26, 2023, by and between Arsenal Biosciences, Inc., as Sublandlord, and Assembly Biosciences, Inc., as Subtenant.	10-Q	11/08/2023	10.1
10.2	First Amendment to Sublease, dated December 30, 2024, by and between Arsenal Biosciences, Inc. and Assembly Biosciences, Inc.	8-K	01/03/2025	10.1
10.3‡	Option, License and Collaboration Agreement, dated October 15, 2023, by and between Assembly Biosciences, Inc. and Gilead Sciences, Inc.	8-K	10/17/2023	10.1
10.4‡	First Amendment to Option, License and Collaboration Agreement, dated December 19, 2024, by and between Assembly Biosciences, Inc. and Gilead Sciences, Inc.	8-K	12/19/2024	10.1
10.5‡	Common Stock Purchase Agreement, dated October 15, 2023, by and between Assembly Biosciences, Inc. and Gilead Sciences, Inc.	8-K	10/17/2023	10.2
10.6	Amendment No. 1 to Common Stock Purchase Agreement, dated June 17, 2024, by and between Assembly Biosciences, Inc. and Gilead Sciences, Inc.	8-K	06/18/2024	10.3
10.7‡	Investor Rights Agreement, dated October 15, 2023, by and between Assembly Biosciences, Inc. and Gilead Sciences, Inc.	8-K	10/17/2023	10.3
10.8	Amendment No. 1 to Investor Rights Agreement, dated June 17, 2024, by and between Assembly Biosciences, Inc. and Gilead Sciences, Inc.	8-K	06/18/2024	10.4
10.9#	Amended and Restated Employment Agreement, dated December 12, 2022, between Assembly Biosciences, Inc. and Jason A. Okazaki.	10-K	03/22/2023	10.7
10.10#	Employment Agreement, dated May 1, 2020, between Assembly Biosciences, Inc. and William E. Delaney IV, Ph.D., effective as of May 27, 2020.	10-K	02/25/2021	10.12
10.11#	Employment Agreement, dated November 8, 2023, between Assembly Biosciences, Inc. and Anuj Gaggar, M.D., Ph.D.	10-K	03/28/2024	10.11
10.12#	Employment Agreement, dated February 10, 2022, between Assembly Biosciences, Inc. and Nicole S. White, Ph.D., effective as of February 16, 2022.	10-K	03/28/2024	10.12
10.13#	2010 Equity Incentive Plan.	S-1/A	10/4/2010	10.14
10.14#	Assembly Biosciences, Inc. Amended and Restated 2014 Stock Incentive Plan.	8-K	06/06/2016	10.1


	ASSEMBLY BIOSCIENCES, INC.

Date: March 20, 2025	By:	/s/ Jason A. Okazaki
	Name:	Jason A. Okazaki
	Title:	Chief Executive Officer and President


Signature	Title	Date

/s/ Jason A. Okazaki	Chief Executive Officer, President and Director	March 20, 2025
Jason A. Okazaki	(Principal Executive Officer and Principal Financial Officer)
/s/ Jeanette M. Bjorkquist	Executive Director, Accounting and Treasury	March 20, 2025
Jeanette M. Bjorkquist	(Principal Accounting Officer)

/s/ William R. Ringo, Jr.	Chairman of the Board	March 20, 2025
William R. Ringo, Jr.

/s/ Anthony E. Altig	Director	March 20, 2025
Anthony E. Altig

/s/ Tomas Cihlar, Ph.D.	Director	March 20, 2025
Tomas Cihlar, Ph.D.

/s/ Gina Consylman	Director	March 20, 2025
Gina Consylman

/s/ Robert D. Cook II	Director	March 20, 2025
Robert D. Cook II

/s/ Sir Michael Houghton, Ph.D.	Director	March 20, 2025
Sir Michael Houghton, Ph.D.

/s/ Lisa R. Johnson-Pratt, M.D.	Director	March 20, 2025
Lisa R. Johnson-Pratt, M.D.

/s/ Susan Mahony, Ph.D.	Director	March 20, 2025
Susan Mahony, Ph.D.

/s/ John G. McHutchison, A.O., M.D.	Director	March 20, 2025
John G. McHutchison, A.O., M.D.


	Page
Report of Independent Registered Public Accounting Firm (PCAOB ID: 42)	F-2
Consolidated Balance Sheets as of December 31, 2024 and 2023	F-4
Consolidated Statements of Operations and Comprehensive Loss for the Years Ended December 31, 2024 and 2023	F-5
Consolidated Statements of Changes in Stockholders’ Equity for the Years Ended December 31, 2024 and 2023	F-6
Consolidated Statements of Cash Flows for the Years Ended December 31, 2024 and 2023	F-7
Notes to Consolidated Financial Statements	F-8


		Collaboration Agreement with Gilead Sciences, Inc.
Description of the Matter		As described in Note 8 to the consolidated financial statements, in December 2024, the Company entered into the First Amendment to its 2023 Gilead Collaboration Agreement, which restructured the timing of specific options exercisable in the agreement and the fees payable to the Company. The Company determined the First Amendment to the Gilead Collaboration Agreement represents a contract modification within the scope of the revenue from contracts with customers guidance. The Company concluded there is a single combined performance obligation for the discovery, research and development services during the remaining collaboration term, and will recognize revenue over time using a cost-based input method consisting of a series of distinct R&D Services. As of December 31, 2024, the total transaction price was determined to be $74.2 million, consisting of the unrecognized portion of the transaction price under the original contract, a premium of $5.2 million on Gilead's purchase of the Company's common stock in December 2024, and $10.0 million received from Gilead pursuant to the First Amendment to the Gilead Collaboration Agreement. Auditing the Company’s accounting for the First Amendment to the Gilead Collaboration Agreement required increased audit effort due to the complex and judgmental nature of evaluating the terms and assumptions of the related amendment and the appropriate accounting for the modification under the guidance.
How We Addressed the Matter in Our Audit		To test the conclusion that the modification was accounted for appropriately, our audit procedures included, among others, reviewing the First Amendment to the Gilead Collaboration Agreement and evaluating whether management's accounting position considered all relevant facts and terms included in the agreement. We further evaluated management's technical analysis and assessed management's conclusions to determine whether they had appropriately considered and applied the guidance and associated interpretations.


	Common Stock				Additional Paid-in		Accumulated Other Comprehensive			Accumulated			Total Stockholders'
	Shares		Amount		Capital		Loss			Deficit			Equity
Balance as of December 31, 2022		4,074,552	$	4	$	807,983	$	(803	)	$	(724,520	)	$	82,664
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs		261,170		—		4,546		—			—			4,546
Issuance of common stock in a private placement to a related party, net of issuance costs		1,089,472		1		9,142		—			—			9,143
Issuance of common stock under Employee Stock Purchase Plan (ESPP)		14,453		—		129		—			—			129
Issuance of common stock for settlement of restricted stock units (RSUs)		43,105		—		—		—			—			—
Unrealized gain on marketable debt securities		—		—		—		722			—			722
Stock-based compensation		—		—		5,121		—			—			5,121
Net loss		—		—		—		—			(61,228	)		(61,228	)
Balance as of December 31, 2023		5,482,752	$	5	$	826,921	$	(81	)	$	(785,748	)	$	41,097
Issuance of common stock under ATM equity offering program, net of issuance costs		152,666		—		2,030		—			—			2,030
Issuance of common stock and warrants in a registered direct offering, net of issuance costs		634,500		1		9,661		—			—			9,662
Issuance of common stock and warrants in private placements to a related party, net of issuance costs		1,119,999		1		17,601		—			—			17,602
Issuance of common stock upon exercise of stock options		514		—		5		—			—			5
Issuance of common stock under ESPP		14,937		—		150		—			—			150
Issuance of common stock for settlement of RSUs		51,872		—		—		—			—			—
Unrealized loss on marketable debt securities		—		—		—		(130	)		—			(130	)
Stock-based compensation		—		—		3,120		—			—			3,120
Net loss		—		—		—		—			(40,177	)		(40,177	)
Balance as of December 31, 2024		7,457,240	$	7	$	859,488	$	(211	)	$	(825,925	)	$	33,359


Exhibit Number	Description of Document	Registrant’s Form	Dated	Exhibit No.	Filed Herewith
24.1	Power of Attorney (included on signature page).				X
31.1	Certification of the Chief Executive Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.				X
32.1**	Certification of the Chief Executive Officer Pursuant to 18 U.S.C. Section 1350 as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.				X
97.1	Clawback Policy.	10-K	03/28/2024	97.1
101.INS	Inline XBRL Instance Document.
101.SCH	Inline XBRL Taxonomy Extension Schema Document.
101.CAL	Inline XBRL Taxonomy Extension Calculation Linkbase Document.
101.DEF	Inline XBRL Taxonomy Extension Definitions Linkbase Document.
101.LAB	Inline XBRL Taxonomy Extension Label Linkbase Document.
101.PRE	Inline XBRL Taxonomy Extension Presentation Linkbase Document.
104	Cover Page Interactive Data File (embedded within the Inline XBRL document).