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 11, 2026

TEMPEST THERAPEUTICS, INC.

(Exact name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (415) 798-8589

N/A

(Former Name or Former Address, if Changed Since Last Report)

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 (see General Instruction A.2. below):

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. ☐

Securities Purchase Agreement

On September 11, 2026, Tempest Therapeutics, Inc. (the “Company”) entered into a securities purchase agreement (the “Purchase Agreement”) with an institutional investor (the “Investor”), pursuant to which the Company issued and sold in a private placement (the “Private Placement”) pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to 3,105,591 shares of the Company’s common stock, par value $0.001 per share (the “Common Stock”) accompanied by (i) Series C warrants to purchase up to 3,105,591 shares of Common Stock (the “Series C Warrants”) and (ii) Series D warrants to purchase up to 3,105,591 shares of Common Stock (the “Series D Warrants” and, together with the Series C Warrants, the “Common Warrants”). The combined purchase price per Pre-Funded Warrant and accompanying Common Warrants is $0.804. The gross proceeds to the Company from the Private Placement is approximately $2.5 million (excluding up to approximately $5 million of aggregate gross proceeds that may be received in the future upon the cash exercise of the Common Warrants), before deducting placement agent fees and other offering expenses payable by the Company.

The Private Placement closed on September 15, 2026. The Company currently plans to use the net proceeds from the Private Placement primarily for working capital and general corporate purposes.

Pursuant to the Purchase Agreement, the Company agreed to seek, within 90 days following the date of the Purchase Agreement, approval from its stockholders for the issuance of the shares issuable upon exercise of the Common Warrants (the “Stockholder Approval”). The Series C Warrants will become exercisable on the effective date of the Stockholder Approval (the “Stockholder Approval Date”) and have a term of six years from the later of the Stockholder Approval Date and the Effectiveness Date (as defined below). The Series D Warrants will become exercisable on the Stockholder Approval Date and have a term three years from the later of the Stockholder Approval Date and the Effectiveness Date. The Common Warrants have an exercise price of $0.805 per share. The Pre-Funded Warrants are exercisable immediately following the closing date of the Private Placement, have an exercise price of $0.001 per share and may be exercised at any time until exercised in full. In addition, pursuant to the Purchase Agreement, the Company has agreed not to (i) enter into any agreement to issue or announce the issuance or proposed issuance of any shares of Common Stock or Common Stock equivalents, or (ii) file any registration statement or amendment or supplement thereto, for a period of 30 days following the Effective Date, subject to certain customary exceptions. In addition, the Purchase Agreement provides that for a period of 60 days following the Effective Date, the Company will not effect or enter into an agreement to effect a “variable rate transaction” as defined in the Purchase Agreement, subject to certain customary exceptions.

The exercise price and the number of shares of Common Stock issuable upon exercise of the Pre-Funded Warrants and the Common Warrants are subject to customary adjustments in the case of stock dividends, stock splits, pro rata distributions, and similar events in respect of the Common Stock. A holder (together with its affiliates) of the Pre-Funded Warrants or Common Warrants, will not be entitled to exercise any portion of any Pre-Funded Warrant or Common Warrant, which, upon giving effect to such exercise would cause the aggregate number of shares of Common Stock beneficially owned by the holder (together with its affiliates) to exceed 9.99% with respect to the Pre-Funded Warrants or 4.99% (or, upon election of the holder, 9.99%) with respect to the Common Warrants of the number of shares of the Common Stock outstanding immediately after giving effect to the exercise, subject to such holder’s rights under the Pre-Funded Warrants and the Common Warrants to increase or decrease such percentage to another percentage not in excess of 9.99% upon notice from such holder to the Company (at least 61 days’ prior notice in the case of an increase).

The Purchase Agreement contains customary representations, warranties and agreements by the Company, indemnification obligations of the Company, including for liabilities arising under the Securities Act of 1933, as amended (the “Securities Act”), other obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Purchase Agreement were made only for the purposes of such agreement and as of the specific dates, were solely for the benefit of the parties to such agreement and may be subject to limitations agreed upon by the contracting parties.

H.C. Wainwright & Co., LLC (the “Placement Agent”) served as the exclusive placement agent for the Company in connection with the Private Placement pursuant to an engagement letter between the Company and the Placement Agent, pursuant to which the Placement Agent agreed to serve on a reasonable best efforts basis in connection with the Private Placement. The Company agreed to issue to the Placement Agent or its designees warrants to purchase up to 217,391 shares of Common Stock in substantially the same form as the Series C Warrants, except that the exercise price thereunder is $1.0063 per share (the “Placement Agent Warrants”). The Company paid the Placement Agent an aggregate cash fee equal to 7.0% of the gross proceeds received in the Private Placement and reimbursed certain expenses incurred by the Placement Agent in connection with the Private Placement.

Registration Rights Agreement

On September 11, 2026, the Company also entered into a registration rights agreement with the Investor (the “Registration Rights Agreement”), pursuant to which the Company agreed to file a registration statement under the Securities Act with the Securities and Exchange Commission (the “SEC”), covering the resale of the shares of Common Stock underlying the Common Warrants and Pre-Funded Warrants no later than 15 calendar days following the date of the Registration Rights Agreement, and to use reasonable best efforts to have the registration statement declared effective by 45 calendar days following the date of the Registration Rights Agreement, and in any event no later than 75 calendar days following the date of the Registration Rights Agreement in the event of a “full review” by the SEC (the “Effectiveness Date”).

The foregoing description of the terms and conditions of the Purchase Agreement, Registration Rights Agreement, Pre-Funded Warrants and Common Warrants is only a summary and is qualified in its entirety by the full text of the form of Purchase Agreement, form of Registration Rights Agreement, form of Pre-Funded Warrants and form of Common Warrants, copies of which are attached hereto as Exhibits 10.1, 10.2, 4.1 and 4.2, respectively, and incorporated by reference herein.

The information contained above in Item 1.01 relating to the Private Placement is hereby incorporated by reference into this Item 3.02. Based in part upon the representations of the Investor in the Purchase Agreement, the securities described above are being offered and sold in a private placement exempt from registration under the Securities Act pursuant to Section 4(a)(2) thereof and Regulation D promulgated thereunder. Accordingly, such securities may not be offered or sold in the United States except pursuant to an effective registration statement or an applicable exemption from the registration requirement of the Securities Act and applicable state securities laws.

Neither this Current Report on Form 8-K nor any exhibit attached hereto is an offer to sell or the solicitation of an offer to buy shares of Common Stock or other securities of the Company.

(d) Exhibits.

SIGNATURES

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