Seres Therapeutics Inc — Current Report (Form 8-K)

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): July 8, 2026

SERES THERAPEUTICS, INC.

(Exact name of Registrant as Specified in Its Charter)

Registrant’s Telephone Number, Including Area Code: (617) 945-9626

Not Applicable

(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:

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. ☐

As reported below under Item 5.07 of this Current Report on Form 8-K (this “Current Report”), on July 8, 2026, Seres Therapeutics, Inc. (the “Company”) reconvened its 2026 Annual Meeting of Stockholders (the “Annual Meeting”), which had been adjourned from June 9, 2026 due to a lack of quorum. At the Annual Meeting, the Company’s stockholders approved an amendment and restatement of the Seres Therapeutics, Inc. 2025 Incentive Award Plan (the “2025 Plan”) to increase the number of shares of the Company’s common stock available for issuance under the 2025 Plan by 900,000 shares. The amendment and restatement of the 2025 Plan was approved by the Company’s Board of Directors on April 22, 2026, subject to and effective upon stockholder approval of the amendment and restatement of the 2025 Plan at the Annual Meeting.

The terms and conditions of the 2025 Plan, as amended and restated, are described in the section entitled “Proposal 4 — Approval of the Amendment and Restatement of the Seres Therapeutics, Inc. 2025 Incentive Award Plan” in the Company’s definitive proxy statement on Schedule 14A filed with the Securities and Exchange Commission (the “SEC”) on April 27, 2026 (the “Definitive Proxy Statement”). The foregoing description of the 2025 Plan does not purport to be complete and is qualified in its entirety by reference to the complete text of the 2025 Plan, a copy of which is filed as Exhibit 10.1 hereto and is incorporated herein by reference.

On July 8, 2026, at the Annual Meeting, a total of 4,985,176 shares of the Company’s common stock were represented in person or by proxy at the meeting, representing approximately 51.75% of the Company’s outstanding Common Stock as of the April 13, 2026 record date. The following are the voting results for the proposals considered and voted upon at the Annual Meeting, all of which were described in the Company’s Definitive Proxy Statement.

Item 1 - Election of three Class II directors to serve until the 2029 Annual Meeting of Stockholders, and until their respective successors have been duly elected and qualified.

Item 2 - Ratification of the appointment of PricewaterhouseCoopers LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026.

Item 3 - Approval, on an advisory (non-binding) basis, of the compensation of the Company’s named executive officers.

Item 4 - Approval of an amendment and restatement of the Seres Therapeutics, Inc. 2025 Plan to increase the number of shares available for issuance under the plan.

Item 5 - Approval of an adjournment of the Annual Meeting, if necessary, to solicit additional proxies if there were not sufficient votes at the time of the Annual Meeting to approve Proposal 4.

Based on the foregoing votes, the director nominees listed in Item 1 were elected and Items 2 through 5 were approved. Although Item 5 was approved, an adjournment of the Annual Meeting was not necessary because the Company’s stockholders approved Proposal 4.

(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.