UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15 (d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported):  September 8, 2026

United Therapeutics Corporation

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (301) 608-9292

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company      ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.   ¨

On September 8, 2026, United Therapeutics Corporation (the Company) entered into an accelerated share repurchase agreement (the ASR Agreement) with Citibank, N.A. (Citi) to repurchase approximately $477.6 million in the aggregate of the Company’s common stock (Common Stock) under the Company’s previously announced share repurchase program (the Share Repurchase Program).

Under the terms of the ASR Agreement, the Company will make an aggregate upfront payment of approximately $477.6 million to Citi on or around September 10, 2026 and will receive an initial delivery of approximately 719,376 shares of Common Stock, representing approximately 75% of the total shares that would be repurchased under the ASR Agreement measured based on the closing price of the Common Stock on September 8, 2026.

The exact number of shares that the Company will ultimately repurchase pursuant to the ASR Agreement will be determined based on the average of the daily volume-weighted average price per share of the Common Stock during the term of the ASR Agreement, less a discount and subject to adjustments pursuant to the terms and conditions of the ASR Agreement. The final settlement of the ASR Agreement is expected to be completed in the fourth quarter of 2026.

At final settlement of the ASR Agreement, the Company may be entitled to receive additional shares of Common Stock, or, in certain limited circumstances, be required to make a cash payment to Citi or, if the Company elects, deliver shares to Citi.

The ASR Agreement contains customary terms for these types of transactions, including, but not limited to, the mechanisms used to determine the number of shares of Common Stock or the amount of cash that will be delivered at settlement, the required timing of delivery of the shares of Common Stock, the specific circumstances under which adjustments may be made to the transactions, the specific circumstances under which final settlement of the ASR Agreement may be accelerated or extended, the specific circumstances under which the transactions may be terminated prior to their scheduled maturity, and various acknowledgements, representations and warranties made by the Company and Citi to one another.

The foregoing description of the ASR Agreement does not purport to be complete and is qualified in its entirety by reference to the master confirmation governing the ASR Agreement, a copy of which the Company filed with the U.S. Securities and Exchange Commission on March 25, 2024 as Exhibit 10.1 to the Company’s Current Report on Form 8-K and is incorporated herein by reference.

On September 8, 2026, the Company issued a press release announcing the ASR Agreement. A copy of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

The information in this Item 7.01 and Exhibit 99.1 attached hereto are being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the Exchange Act), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, regardless of any general incorporation language in such filing.

(d)    Exhibits

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.