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 23, 2025

SERES THERAPEUTICS, INC.

(Exact name of Registrant as Specified in Its Charter)

Delaware

001-37465

27-4326290

(State or other jurisdiction

of incorporation)

(Commission

File Number)

(IRS Employer

Identification No.)


101 Cambridgepark Drive
Cambridge, MA		02140
(Address of principal executive offices)		(Zip Code)

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:

☐	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each class

Trading
Symbol(s)

Name of each exchange

on which registered

Common stock, par value $0.001 per share

MCRB

The Nasdaq Stock Market LLC

(Nasdaq Global Select Market)

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. ☐

Item 8.01.

Other Events.

On September 23, 2025, Seres Therapeutics, Inc. (the “Company”) announced actions to reduce operating costs in order to extend its cash runway to provide additional opportunities to advance its strategic priorities.

In this announcement, the Company reported that it was reducing its workforce by approximately 25% (including reductions that were effective in August 2025), and the workforce reduction is expected to result in cash charges of approximately $1.0 to $1.4 million, primarily related to severance costs, to be paid in the fourth quarter of 2025. As a result of the anticipated cost savings arising from these previously announced initiatives, and based on current operating plans, the Company expects to extend its cash runway into the second quarter of 2026. The foregoing estimates are based upon current assumptions and expectations but are subject to known and unknown risks and uncertainties. Accordingly, the Company may not be able to fully realize the cost savings and benefits initially anticipated from such actions, and the expected costs may be greater than expected.

Forward-Looking Statements

This Current Report on Form 8-K (this “Current Report”) contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this Current Report that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation statements regarding cost saving initiatives, including anticipated workforce reductions, restructuring charges, cash savings, operating plans and our cash runway, and the timing of any of the foregoing. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause the Company’s actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: (1) our need for additional funding; (2) our ability to continue as a going concern; (3) we have incurred significant losses, are not currently profitable and may never become profitable; (4) our history of operating losses; (5) our cost savings initiative may not be successful, and may not have its anticipated benefits; (6) our ability to manage our recent CEO transition, to retain key personnel and to manage our growth; and the other important factors discussed under the caption “Risk Factors” in the Company’s Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025, and the Company’s other reports filed with the Securities and Exchange Commission could cause actual results to differ materially from those indicated by the forward-looking statements made in this Current Report. Any such forward-looking statements represent management’s estimates as of the date of this Current Report. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause the Company’s views to change. These forward-looking statements should not be relied upon as representing the Company’s views as of any date subsequent to the date of this Current Report.

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.

SERES THERAPEUTICS, INC.

Date: October 3, 2025

/s/ Thomas J. DesRosier

Thomas J. DesRosier

Co-Chief Executive Officer, Co-President,

Executive Vice President, Chief Legal Officer and Secretary

Seres Therapeutics, Inc. 8-K