As filed with the U.S. Securities and Exchange Commission on March 30, 2026

Registration No. 333-   

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Tempest Therapeutics, Inc.

(Exact name of Registrant as specified in its charter)

2000 Sierra Point Parkway, Suite 400

Brisbane, California 94005

(415) 798-8589

(Address of principal executive offices) (Zip code)

Tempest Therapeutics, Inc. Amended and Restated 2023 Equity Incentive Plan

Tempest Therapeutics, Inc. Amended and Restated 2019 Employee Stock Purchase Plan

(Full titles of the plans)

Matthew Angel

Chief Executive Officer

Tempest Therapeutics, Inc.

2000 Sierra Point Parkway, Suite 400

Brisbane, California 94005

(415) 798-8589

(Name, address and telephone number, including area code, of agent for service)

Copies to:

Laura Berezin

Jaime Chase

Cooley LLP

1700 Seventh Avenue, Suite 1900

Seattle, Washington 98101

(206) 452-8700

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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 7(a)(2)(B) of the Securities Act.

EXPLANATORY NOTE

Tempest Therapeutics, Inc. (the “Registrant”) is filing this Registration Statement on Form S-8 for the purpose of registering (a) 197,086 additional shares of its common stock, par value $0.001 per share (the “Common Stock”), issuable to eligible persons under the Registrant’s Amended and Restated 2023 Equity Incentive Plan (the “2023 Plan”) pursuant to the provisions of the 2023 Plan providing for an automatic increase in the number of shares of Common Stock reserved and available for issuance under the 2023 Plan on January 1, 2026, (b) 1,410,000 additional shares of Common Stock, issuable to eligible persons under the 2023 Plan, pursuant to an amendment to the 2023 Plan approved by the Company’s stockholders on January 27, 2026, and (c) 38,461 additional shares of Common Stock issuable to eligible persons under the Registrant’s Amended and Restated 2019 Employee Stock Purchase Plan (the “2019 ESPP”) pursuant to the provisions of the 2019 ESPP providing for an automatic increase in the number of shares of Common Stock reserved and available for issuance under the 2019 ESPP on January 1, 2026.

In accordance with the instructional note to Part I of Form S-8 as promulgated by the Securities and Exchange Commission (the “SEC”), the information specified by Part I of the Form S-8 has been omitted from this Registration Statement.

PART II

Item 3. Incorporation of Certain Documents By Reference

The following documents filed by the Registrant with the SEC are incorporated by reference into this Registration Statement:

(a) the contents of the Registrant’s Registration Statements on Form S-8, previously filed with the SEC on December 16, 2019 (File No.  333-235515), November 10, 2020 (File No. 333-249993), April  15, 2021 (File No. 333-255261), May  13, 2022 (File No. 333-264943), June  21, 2022 (File No. 333-265718), each as amended by the Post-Effective Amendments to Form S-8 filed on November  17, 2023 (File Nos. 333-265718, 333-264943, 333-255261, 333-249993 and 333-235515), November  17, 2023 (File No. 333-275637), March  19, 2024 (File No. 333-278071); and March  27, 2025 (File No. 333-286186);

(b) the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the SEC on March 30, 2026 (File No. 001-35890);

(c) the Registrant’s Current Reports on Form 8-K, filed with the SEC on January 9, 2026, January  28, 2026, February  6, 2026, February  25, 2026 and March 23, 2026, to the extent the information in such reports is filed and not furnished; and

(d) the description of the Common Stock set forth in the Registrant’s registration statement on Form 8-A (File No. 001-35890), filed with the Commission on April 25, 2013, including any amendments thereto or reports filed for the purposes of updating this description, including Exhibit 4.1 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025 filed with the SEC on March 30, 2026.

All reports and documents subsequently filed by the Registrant pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act (other than Current Reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits furnished on such form that relate to such items) on or after the date of this Registration Statement and prior to the filing of a post-effective amendment to this Registration Statement which indicates that all securities offered have been sold or which deregisters all securities then remaining unsold, shall be deemed to be incorporated by reference herein and to be a part of this Registration Statement from the date of the filing of such reports and documents. Any statement contained in a document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for purposes of this Registration Statement to the extent that a statement contained herein or in any subsequently filed document that also is deemed to be incorporated by reference herein modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this Registration Statement.

Item 8. Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in Brisbane, State of California, on March 30, 2026.

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Matthew Angel and Nicholas Maestas, and each one of them, as his or her true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution, for him or her and in their name, place, and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement, and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or his or her substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, as amended, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

Exhibit 5.1

March 30, 2026

Jaime L. Chase

+1 202 728-7096

jchase@cooley.com

Tempest Therapeutics, Inc.

2000 Sierra Point Parkway, Suite 400

Brisbane, California 94005

Ladies and Gentlemen:

We have acted as counsel to Tempest Therapeutics, Inc., a Delaware corporation (the “Company”), in connection with the filing by the Company of a Registration Statement on Form S-8 (the “Registration Statement”) with the Securities and Exchange Commission (the “Commission”) covering the offering of up to 1,645,547 shares (the “Shares”) of the Company’s Common Stock, $0.001 par value, consisting of (a) 1,607,086 shares of Common Stock issuable pursuant to the Company’s Amended and Restated 2023 Equity Incentive Plan, as amended (the “2023 EIP”), and (b) 38,461 additional shares of Common Stock issuable pursuant to the Company’s Amended and Restated 2019 Employee Stock Purchase Plan (the “2019 ESPP” and together with the 2023 EIP, the “Plans”). Each share of Common Stock includes a preferred share purchase right (each, a “Right,” collectively, the “Rights”) as set forth in Rights Agreement (the “Rights Plan”), dated as October 10, 2023, as amended, between the Company and Computershare Trust Company, N.A., as rights agent (the “Rights Agent”).

In connection with this opinion, we have examined and relied upon: (a) the Registration Statement and related prospectuses, (b) the Plans, (c) the Company’s certificate of incorporation and bylaws, each as currently in effect, (d) the Rights Plan and (e) such other records, documents certificates, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below. We have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to originals of all documents submitted to us as copies, the accuracy, completeness and authenticity of certificates of public officials, and the due authorization, execution and delivery of all documents by all persons other than the Company where authorization, execution and delivery are prerequisites to the effectiveness thereof. As to certain factual matters, we have relied upon a certificate of an officer of the Company and have not independently verified such matters.

With respect to our opinion concerning the Rights:

(i) Our opinion does not address the determination a court of competent jurisdiction may make regarding whether the Company’s board of directors (the “Board”) may be required to redeem or terminate, or take other action with respect to, the Rights or Rights Plan in the future based on the facts and circumstances then existing.

(ii) Our opinion assumes that the Rights Plan has been duly authorized, executed and delivered by the Rights Agent and that members of the Board have acted in a manner consistent with their fiduciary duties as required under applicable law in adopting the Rights Plan. With respect to Rights associated with Shares to be offered in the future under the Registration Statement, our opinion assumes the Rights Plan has not been terminated by the Company or expired by its terms and the Rights have not expired or been redeemed or exchanged by the Company, in each case, prior to the issuance of such Shares.

(iii) Our opinion addresses corporate procedures in connection with the issuance of the Rights associated with the Shares of the Company, and not any particular provision of the Rights or the Rights Plan. It should be understood that it is not settled whether the invalidity of any particular provision of a rights agreement or purchase rights issued thereunder would invalidate such rights in their entirety.

Cooley LLP 1299 Pennsylvania Avenue NW Suite 700 Washington, DC 20004-2400

t: +1 202 842 7800 f: +1 202 842 7899 cooley.com

Our opinion is expressed only with respect to the General Corporation Law of the State of Delaware. We express no opinion to the extent that any other laws are applicable to the subject matter hereof and express no opinion and provide no assurance as to compliance with any federal or state securities law, rule or regulation.

On the basis of the foregoing, and in reliance thereon, and subject to the qualifications herein stated, we are of the opinion that the Shares and associated Rights, when sold and issued against payment therefor in accordance with the Plans, the Registration Statement and the related prospectuses, will be validly issued, and the Shares will be fully paid and nonassessable (except as to shares issued pursuant to deferred payment arrangements, which will be fully paid and nonassessable when such deferred payments are made in full).

This opinion is limited to the matters expressly set forth in this letter, and no opinion should be implied, or may be inferred, beyond the matters expressly stated. This opinion speaks only as to law and facts in effect or existing as of the date hereof, and we have no obligation or responsibility to update or supplement this opinion to reflect any facts or circumstances that may hereafter come to our attention or any changes in law that may hereafter occur.

We consent to the filing of this opinion as an exhibit to the Registration Statement. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act of 1933, as amended, or the rules and regulations of the Commission thereunder.

Sincerely,

Cooley LLP 1299 Pennsylvania Avenue NW Suite 700 Washington, DC 20004-2400

t: +1 202 842 7800 f: +1 202 842 7899 cooley.com

Exhibit 23.2

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the Tempest Therapeutics, Inc. Amended and Restated 2023 Equity Incentive Plan and the Tempest Therapeutics, Inc. Amended and Restated 2019 Employee Stock Purchase Plan of our report dated March 30, 2025, with respect to the consolidated financial statements of Tempest Therapeutics, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2025, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Chicago, Illinois

March 30, 2026