As filed with the Securities and Exchange Commission on May 7, 2025

Registration No. 333-   

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

SERES THERAPEUTICS, INC.

(Exact Name of Registrant as Specified in Its Charter)

101 Cambridgepark Drive

Cambridge, MA 02140

(Address of Principal Executive Offices) (Zip Code)

Seres Therapeutics, Inc. 2025 Incentive Award Plan

(Full Title of the Plan)

Eric D. Shaff.

President and Chief Executive Officer

Seres Therapeutics, Inc.

101 Cambridgepark Drive

Cambridge, MA 02140

(Name and Address of Agent for Service)

(617) 945-9626

(Telephone Number, including Area Code, of Agent for Service)

Copies to:

Peter N. Handrinos, Esq.

Latham & Watkins LLP

200 Clarendon Street

Boston, MA 02116

(617) 948-6060

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 new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

EXPLANATORY NOTE

This Registration Statement on Form S-8 is being filed for the purpose of registering 479,750 shares of the Registrant’s common stock to be issued pursuant to the Seres Therapeutics, Inc. 2025 Incentive Award Plan (the “2025 Plan”). On April 10, 2025, the Registrant’s stockholders approved the amendment and restatement of the Seres Therapeutics, Inc. 2015 Incentive Award Plan (the “2015 Plan”) to, among other things, authorize the issuance of 2,230,243 shares of the Registrant’s common stock for awards under the amended and restated 2015 Plan, which includes 1,750,493 shares previously authorized for issuance under the 2015 Plan plus an increase of 479,750 shares, and extend the term of the amended and restated 2015 Plan to March 3, 2035. In connection with amending and restating the 2015 Plan, the name of the 2015 Plan was updated to the 2025 Plan.

INCORPORATION BY REFERENCE OF CONTENTS OF

REGISTRATION STATEMENTS ON FORM S-8

The contents of the Registration Statements on Form S-8 (File Nos. 333-205253, 333-210171, 333-223514, 333-230092, 333-236824, 333-253776, 333-263134, 333-270319, 333-277658 and 333-285769), including any amendments thereto, filed with the Securities and Exchange Commission, relating to the 2025 Plan (as an amendment and restatement of the 2015 Plan), are incorporated by reference herein.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, 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 the City of Cambridge, Commonwealth of Massachusetts, on this 7^th day of May, 2025.

POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Eric D. Shaff and Marella Thorell, or either 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 his or her name, place and stead, in any and all capacities, to file and sign any and all amendments, including post-effective amendments, to this registration statement, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, 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 their substitute or substitutes may lawfully do or cause to be done by virtue hereof. This power of attorney shall be governed by and construed with the laws of the State of Delaware and applicable federal securities laws.

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

Exhibit 5.1

		200 Clarendon Street
		Boston, Massachusetts 02116
		Tel: +1.617.948.6000 Fax: +1.617.948.6001 www.lw.com
		FIRM / AFFILIATE OFFICES
		Austin		Milan
		Beijing		Munich
		Boston		New York
		Brussels		Orange County
		Century City		Paris
		Chicago		Riyadh
		Dubai		San Diego
		Düsseldorf		San Francisco
		Frankfurt		Seoul
		Hamburg		Silicon Valley
		Hong Kong		Singapore
		Houston		Tel Aviv
		London		Tokyo
		Los Angeles		Washington, D.C.
		Madrid

May 7, 2025

Seres Therapeutics, Inc.

101 Cambridgepark Drive

Cambridge, MA 02140

To the addressee set forth above:

We have acted as special counsel to Seres Therapeutics, Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing by the Company with the Securities and Exchange Commission (the “Commission”) of a registration statement on Form S-8 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Act”), relating to the issuance by the Company of up to 479,750 shares of common stock of the Company, $0.001 par value per share (the “Shares”), issuable under the Seres Therapeutics, Inc. 2025 Incentive Award Plan (the “Plan”). This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or the prospectus forming a part thereof, other than as expressly stated herein with respect to the issuance of the Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to the General Corporation Law of the State of Delaware (the “DGCL”), and we express no opinion with respect to any other laws.

May 7, 2025

Page 2

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, when the Shares shall have been duly registered on the books of the transfer agent and registrar therefor in the name or on behalf of the purchasers, and have been issued by the Company for legal consideration in excess of par value in the circumstances contemplated by the Plan, assuming in each case that the individual grants or awards under the Plan are duly authorized by all necessary corporate action and duly granted or awarded and exercised in accordance with the requirements of law and the Plan (and the agreements and awards duly adopted thereunder and in accordance therewith), the issue and sale of the Shares will have been duly authorized by all necessary corporate action of the Company, and the Shares will be validly issued, fully paid and nonassessable. In rendering the foregoing opinion, we have assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the DGCL.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing 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 Act or the rules and regulations of the Commission thereunder.

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in this Registration Statement on Form S-8 of Seres Therapeutics, Inc. of our report dated March 13, 2025 relating to the financial statements and the effectiveness of internal control over financial reporting, which appears in Seres Therapeutics, Inc.’s Annual Report on Form 10-K for the year ended December 31, 2024.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

May 7, 2025

Exhibit 107

CALCULATION OF FILING FEE TABLE

FORM S-8

(Form Type)

SERES THERAPEUTICS, INC.

(Exact Name of Registrant as Specified in its Charter)

Table I: Newly Registered Securities