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): August 13, 2024

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. ☐

On August 13, 2024, Seres Therapeutics, Inc. (the “Company”) announced its financial results for the quarter ended June 30, 2024 and provided operational updates. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K (the “Current Report”).

Item 7.01. Regulation FD Disclosure.

On August 13, 2024, the Company posted an updated corporate presentation in the “Investors and News” portion of its website at www.serestherapeutics.com. A copy of the slide presentation is attached as Exhibit 99.2 to this Current Report on Form 8-K and incorporated herein by reference.

The information in this Items 2.02 and 7.01 of this Current Report, including Exhibits 99.1 and 99.2 attached hereto, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act, except as expressly set forth by specific reference in such filing.

(d) Exhibits

The following Exhibits 99.1 and 99.2 relate to Items 2.02 and 7.01, respectively, and shall be deemed to be furnished, and not filed:

Important Additional Information About the Transaction and Where to Find It

This communication is being made in respect of the proposed transaction involving Seres and SPN. Seres intends to file with the Securities and Exchange Commission (the “SEC”), a proxy statement and other relevant documents in connection with a special meeting of Seres’ stockholders for purposes of obtaining, stockholder approval of the proposed transaction. The definitive proxy statement will be sent or given to the stockholders of Seres and will contain important information about the proposed transaction and related matters. INVESTORS AND STOCKHOLDERS OF SERES ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT AND OTHER RELEVANT MATERIALS CAREFULLY AND IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT SERES AND THE PROPOSED TRANSACTION. Investors may obtain a free copy of these materials (when they are available) and other documents filed by Seres with the SEC at the SEC’s website at www.sec.gov or from Seres at its website at ir.serestherapeutics.com.

Participants in the Solicitation

Seres and certain of its directors, executive officers and other members of management and employees may be deemed to be participants in soliciting proxies from its stockholders in connection with the proposed transaction. Information regarding the persons who may, under the rules of the SEC, be considered to be participants in the solicitation of Seres’ stockholders in connection with the proposed transaction will be set forth in Seres’ definitive proxy statement for its stockholder meeting at which the proposed transaction will be submitted for approval by Seres’ stockholders. You may also find additional information about Seres’ directors and executive officers in Seres’ Annual Report on Form 10-K for the fiscal year ended December 31, 2023, which was filed with the SEC on March 5, 2024, Seres’ Definitive Proxy Statement for its 2024 annual meeting of stockholders, which was filed with the SEC on March 5, 2024, and in subsequently filed Current Reports on Form 8-K and Quarterly Reports on Form 10-Q.

Forward-Looking Statements

This communication contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this communication that do not relate to matters of historical fact should be considered forward-looking statements, including statements about the financial terms, timing and completion of the sale of VOWST assets to SPN; the receipt of future payments and the use of proceeds of the transaction,; the timing and results of our clinical studies and data readouts; future product candidates, development plans and commercial opportunities; operating plans and our future cash runway; our ability to generate additional capital; our planned strategic focus; anticipated timing of any of the foregoing and other statements which are not historical fact.

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 our 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) we have incurred significant losses, are not currently profitable and may never become profitable; (2) our need for additional funding; (3) our history of operating losses; (4) the restrictions in our debt agreement; (5) our novel approach to therapeutic intervention; (6) our reliance on third parties to conduct our clinical trials and manufacture our product candidates; (7) the competition we will face; our ability to protect our intellectual property; (8) our ability to retain key personnel and to manage our growth; (9) the occurrence of any event, change or other circumstance that could give rise to the termination of the Purchase Agreement; (10) our failure to obtain stockholder approval for the proposed transaction or to satisfy any of the other conditions to the completion of the proposed transaction; (11) the effect of the announcement of the proposed transaction on our ability to retain and hire key personnel and maintain relationships with our customers, suppliers, advertisers, partners and others with whom we do business, or on our operating results and businesses generally; (12) the risks associated with the disruption of management’s attention from ongoing business operations due to the proposed transaction and the obligation to provide transition services; (13) our failure to receive the installment payments or the milestone payments in the future; (14) the significant costs, fees and expenses related to the proposed transaction; (15) the uncertainty of impact of the 50/50 profit and loss sharing arrangement on our reported results and liquidity; (16) the risk that the proposed transaction will not be completed within the expected time period or at all and (17) we may not be able to realize the anticipated benefits of the proposed transaction. These and other important factors discussed under the caption ”Risk Factors” in our Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC), on May 8, 2024, and our other reports filed with the SEC could cause actual results to differ materially from those indicated by the forward-looking statements made in this communication. Any such forward-looking statements represent management’s estimates as of the date of this communication. 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 our views to change. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this communication.

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.

Exhibit 99.1

SERES THERAPEUTICS REPORTS SECOND QUARTER 2024 FINANCIAL RESULTS AND PROVIDES BUSINESS UPDATES

SER-155 Phase 1b placebo-controlled Cohort 2 clinical readout on track for September

VOWST asset sale to provide $175M cash infusion, less approximately $20M in settlement of net obligations between the Parties, at close

Transaction proceeds to fully retire debt and support advancement of wholly-owned cultivated live biotherapeutic pipeline to improve patient outcomes in medically vulnerable populations

Based on existing cash, deal economics and operating plans, Seres expects to fund operations into Q4 2025

Conference call at 8:30 a.m. ET today

CAMBRIDGE, Mass.—August 13, 2024 — Seres Therapeutics, Inc. (Nasdaq: MCRB), (“Seres” or “the Company”), a leading live biotherapeutics company, today reported second quarter 2024 financial results and provided business updates.

“Our recently announced VOWST asset sale will, pending approval by stockholders and upon closing, significantly strengthen Seres’ balance sheet and advance our goal to improve patient outcomes in medically vulnerable patient populations through the use of our wholly-owned cultivated live biotherapeutics,” said Eric Shaff, President and Chief Executive Officer of Seres. “We intend to leverage our clinical, CMC, and regulatory successes by applying our therapeutic approach to new patient groups that face heightened risks of serious bacterial infections, which frequently lead to extensive and costly treatments and, unfortunately too often, death.”

Mr. Shaff continued, “Our lead SER-155 program remains on track for a clinical data readout from the placebo-controlled study Cohort 2 in patients receiving allogeneic hematopoietic stem cell transplant (allo-HSCT) in September. This dataset has the potential to highlight the extensive clinical value and commercial opportunities of both our SER-155 program and our biotherapeutic approach more generally. Multiple patient groups are known to experience a disrupted gastrointestinal (GI) microbiome and a high risk of life-threatening enteric-derived bacterial infections as well as blood stream infections arising from translocated bacteria. Our development efforts are targeting multiple medically vulnerable patient groups, including potentially those with chronic liver disease, cancer neutropenia and solid organ transplants. In the longer term, we plan to develop our biotherapeutics to treat GI-related immune diseases such as inflammatory bowel disease.”

Corporate Highlights

VOWST Commercial Performance

Seres collaborator SPN and certain of its affiliates (collectively, “Nestlé Health Science”) have continued to lead VOWST commercialization efforts. Since the VOWST product launch in June 2023, the breadth of utilization has steadily increased among healthcare providers. Second quarter 2024 net sales were approximately $14.4 million, reflecting an increase of approximately 43% compared to first quarter net sales of $10.1 million. Seres shares equally with Nestlé Health Science in the VOWST commercial profits or losses. Seres’ share of the VOWST net loss for the second quarter of 2024 was $6.6 million, which was included in the Company’s operating results within Collaboration (profit) loss sharing-related party.

Financial Results

Cash Runway

Seres plans to use the capital obtained from the VOWST asset sale transaction to fully retire its senior secured debt facility with Oaktree Capital Management. Additionally, the Bacthera manufacturing contract will be terminated upon close of the transaction, and Seres will have no further obligations to Bacthera.

Various VOWST-related capabilities, including product manufacturing, will transition to Nestlé Health Science as part of the asset sale. As a result, Seres expects that more than a third of its employees will transfer to Nestlé Health Science following the close of the transaction. Moving forward, Seres will be a streamlined and more focused organization, and the Company’s cash burn rate is expected to be reduced.

As of June 30, 2024, Seres had $71.2 million in cash and cash equivalents. Based on existing cash and operating plans, expected cash to be received upon the close of the VOWST sale and related installment payments due in 2025, and ongoing transaction-related obligations, the Company expects to fund operations into the fourth quarter of 2025. Absent the VOWST sale, the Company expects to fund operations into the fourth quarter of 2024.

Conference Call Information

Seres’ management will host a conference call today, August 13, 2024, at 8:30 a.m. ET. The conference call may be accessed by calling 1-800-715-9871 (international callers dial 1-646-307-1963) and referencing the conference ID number 4877586. To join the live webcast, please visit the “Investors and News” section of the Seres website at www.serestherapeutics.com. A webcast replay will be available on the Seres website beginning approximately two hours after the event and will be archived for at least 21 days.

INDICATION AND IMPORTANT SAFETY INFORMATION FOR VOWST

INDICATION

VOWST (fecal microbiota spores, live-brpk) is indicated to prevent the recurrence of Clostridioides difficile infection (CDI) in individuals 18 years of age and older following antibacterial treatment for recurrent CDI (rCDI).

Limitation of Use: VOWST is not indicated for treatment of CDI.

IMPORTANT SAFETY INFORMATION

WARNINGS AND PRECAUTIONS

Transmissible infectious agents: Because VOWST is manufactured from human fecal matter, it may carry a risk of transmitting infectious agents. Report any infection that is suspected to have been transmitted by VOWST to Aimmune Therapeutics, Inc. at 1-833-246-2566.

Potential presence of food allergens: VOWST may contain food allergens. The potential to cause adverse reactions due to food allergens is unknown.

ADVERSE REACTIONS

The most common adverse reactions (reported in ≥5% of participants) were abdominal distension (31.1%), fatigue (22.2%), constipation (14.4%), chills (11.1%) and diarrhea (10.0%).

To report SUSPECTED ADVERSE REACTIONS, contact Aimmune Therapeutics at 1-833-AIM-2KNO (1-833-246-2566), or the FDA at 1-800-FDA-1088, or visit www.fda.gov/MedWatch.

DRUG INTERACTIONS

Do not administer antibacterials concurrently with VOWST.

Please see Full Prescribing Information and Patient Information

About SER-155

The SER-155 composition is designed to prevent GI-derived infections and resulting bloodstream infections, enhance epithelial barrier integrity, and induce immune tolerance responses, to reduce the incidence of GvHD. SER-155 is being evaluated in a Phase 1b placebo-controlled study in patients undergoing allo-HSCT. SER-155 is a consortium of bacterial species selected and optimized using Seres’ reverse translation discovery and development platform technologies. The design incorporates biomarker data from human clinical data, nonclinical human cell-based assays and in vivo disease models. SER-155 has received FDA Fast Track Designation.

About Seres Therapeutics

Seres Therapeutics, Inc. (Nasdaq: MCRB) is a commercial-stage company focused on improving patient outcomes in medically vulnerable populations through novel live biotherapeutics. Seres led the successful development and approval of VOWST^™, the first FDA-approved orally administered microbiome therapeutic. The Company is evaluating SER-155 in a Phase 1b study in patients receiving allo-HSCT. SER-155 is designed to prevent GI-derived infections and resulting bloodstream infections, enhance epithelial barrier integrity and induce immune tolerance responses to reduce the incidence of GvHD. The Company is also advancing additional cultivated oral microbiome therapeutic candidates for medically vulnerable populations, including those with chronic liver disease, cancer neutropenia and solid organ transplants. For more information, please visit www.serestherapeutics.com.

Important Additional Information About the Transaction and Where to Find It

This communication is being made in respect of the proposed transaction involving Seres Therapeutics, Inc., a Delaware corporation (“Seres”) and Société des Produits Nestlé S.A., a société anonyme organized under the laws of Switzerland (“SPN”). Seres intends to file a proxy statement and other relevant documents with the Securities and Exchange Commission (the “SEC”) in connection with a special meeting of Seres’ stockholders for purposes of obtaining, stockholder approval of the proposed transaction. The definitive proxy statement will be sent or given to the stockholders of Seres and will contain important information about the proposed transaction and related matters. INVESTORS AND STOCKHOLDERS OF SERES ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT AND OTHER RELEVANT MATERIALS CAREFULLY AND IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT SERES AND THE PROPOSED TRANSACTION. Investors may obtain a free copy of these materials (when they are available) and other documents filed by Seres with the SEC at the SEC’s website at www.sec.gov or from Seres at its website at ir.serestherapeutics.com.

Participants in the Solicitation

Seres and certain of its directors, executive officers and other members of management and employees may be deemed to be participants in soliciting proxies from its stockholders in connection with the proposed transaction. Information regarding the persons who may, under the rules of the SEC, be considered to be participants in the solicitation of Seres’ stockholders in connection with the proposed transaction will be set forth in Seres’ definitive proxy statement for its stockholder meeting at which the proposed transaction will be submitted for approval by Seres’ stockholders. You may also find additional information about Seres’ directors and executive officers in Seres’ Annual Report on Form 10-K for the fiscal year ended December 31, 2023, which was filed with the SEC on March 5, 2024, Seres’ Definitive Proxy Statement for its 2024 annual meeting of stockholders, which was filed with the SEC on March 5, 2024, and in subsequently filed Current Reports on Form 8-K and Quarterly Reports on Form 10-Q.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including statements about the financial terms, timing and completion of the sale of VOWST assets to Nestlé Health Science; the receipt of future payments and the use of proceeds of the transaction; the timing and results of our clinical studies and data readouts; future product candidates, development plans and commercial opportunities; operating plans and our future cash runway; our ability to generate additional capital; our planned strategic focus; anticipated timing of any of the foregoing and other statements which are not historical fact.

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 our 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) we have incurred significant losses, are not currently profitable and may never become profitable; (2) our need for additional funding; (3) our history of operating losses; (4) the restrictions in our debt agreement; (5) our novel approach to therapeutic intervention; (6) our reliance on third parties to conduct our clinical trials and manufacture our product candidates; (7) the competition we will face; our ability to protect our intellectual property; (8) our ability to retain key personnel and to manage our growth; (9) the occurrence of any event, change or other circumstance that could give rise to the termination of the Purchase Agreement; (10)

our failure to obtain stockholder approval for the proposed transaction or to satisfy any of the other conditions to the completion of the proposed transaction; (11) the effect of the announcement of the proposed transaction on our ability to retain and hire key personnel and maintain relationships with our customers, suppliers, advertisers, partners and others with whom we do business, or on our operating results and businesses generally; (12) the risks associated with the disruption of management’s attention from ongoing business operations due to the proposed transaction and the obligation to provide transition services; (13) our failure to receive the installment payments or the milestone payments in the future; (14) the significant costs, fees and expenses related to the proposed transaction; (15) the uncertainty of impact of the 50/50 profit or loss sharing arrangement on our reported results and liquidity; (16) the risk that the proposed transaction will not be completed within the expected time period or at all; and (17) we may not be able to realize the anticipated benefits of the proposed transaction. These and other important factors discussed under the caption “Risk Factors” in our Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on May 8, 2024, and our other reports filed with the SEC could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. 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 our views to change. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release.

SERES THERAPEUTICS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(unaudited, in thousands, except share and per share data)

SERES THERAPEUTICS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (INCOME)

(unaudited, in thousands, except share and per share data)

Investor and Media Contact:

IR@serestherapeutics.com

Carlo Tanzi, Ph.D.

Kendall Investor Relations

ctanzi@kendallir.com