# EDGAR Filing Document

**Accession Number:** 0001609809
**File Stem:** 0001193125-25-173985
**Filing Date:** 2025-8
**Character Count:** 67223
**Document Hash:** 1e1d15ed18ce6bf30d1b689a54a14088
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-173985.hdr.sgml**: 20250806

**ACCESSION NUMBER**: 0001193125-25-173985

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 52

**CONFORMED PERIOD OF REPORT**: 20250806

**ITEM INFORMATION**: Results of Operations and Financial Condition

**ITEM INFORMATION**: Regulation FD Disclosure

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20250806

**DATE AS OF CHANGE**: 20250806

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Seres Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001609809
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 274326290
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-37465
- **FILM NUMBER:** 251187408

**BUSINESS ADDRESS:**
- **STREET 1:** 200 SIDNEY STREET
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139
- **BUSINESS PHONE:** 617 945 9626

**MAIL ADDRESS:**
- **STREET 1:** 200 SIDNEY STREET
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Seres Health, Inc.
- **DATE OF NAME CHANGE:** 20140603

?xml version='1.0' encoding='ASCII'? 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): August 6, 2025

## SERES THERAPEUTICS, INC.

#### (Exact name of Registrant as Specified in Its Charter)

---

| | | |
|:---|:---|:---|
| **Delaware** | **001-37465** | **27-4326290** |
| **(State or other jurisdiction**<br> **of incorporation)** | **(Commission**<br> **File Number)** | **(IRS Employer**<br> **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<br>Symbol(s)** | **Name of each exchange**<br> **on which registered** |
| Common stock, par value $0.001 per share | MCRB | The Nasdaq Stock Market LLC<br> (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 2.02.** | **Results of Operations and Financial Condition.**  |

---

On August 6, 2025, Seres Therapeutics, Inc. (the "Company") announced its financial results for the quarter ended June 30, 2025 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 6, 2025, 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 and incorporated herein by reference.

The information in 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, or the Exchange Act, except as expressly set forth by specific reference in such filing.

---

| | |
|:---|:---|
| **Item 9.01.** | **Financial Statements and Exhibits.**  |

---

(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:

---

| | |
|:---|:---|
| **Exhibit**<br> **No.** | **Description** |
| 99.1 | [Seres Therapeutics, Inc. Press Release issued August 6, 2025](d930624dex991.htm) |
| 99.2 | [Seres Therapeutics, Inc. Corporate Presentation as of August 2025](d930624dex992.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

---

------

#### 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. | SERES THERAPEUTICS, INC. |
| Date: August 6, 2025 | By: | /s/ Thomas J. DesRosier |
|  | Name: | Thomas J. DesRosier |
|  | Title: | Co-Chief Executive Officer, Co-President,<br> Executive Vice President, Chief Legal Officer and Secretary |

---

## Exhibit 99.1

**Exhibit 99.1**![LOGO](g930624dsp1jpg.jpg)

**SERES THERAPEUTICS REPORTS SECOND QUARTER 2025 FINANCIAL RESULTS AND PROVIDES BUSINESS UPDATES** 

*Following FDA input, Seres submitted Phase 2 study protocol to FDA for SER-155 for the prevention of bloodstream infections (BSIs) in adults undergoing allogeneic hematopoietic stem cell transplant (allo-HSCT) to treat hematological malignancies* 

*Seres engaging with multiple parties regarding various deal structures, including potential business development and partnerships, intended to secure capital and other resources to enable the clinical advancement of SER-155 and additional live biotherapeutic product candidates* 

*Seres received the $25 million installment payment, as expected, from Nestlé Health Science in July 2025* 

*Conference call at 8:30 a.m. ET today* 

CAMBRIDGE, Mass.—August 6, 2025 — Seres Therapeutics, Inc. (Nasdaq: MCRB), (Seres or the Company), a leading live biotherapeutics company, today reported second quarter 2025 financial results and provided business updates.

"We are in active discussions with multiple parties seeking capital and other resources to support further development of SER-155 for the prevention of BSIs and our broader portfolio of live biotherapeutic product candidates with applications for inflammatory diseases. The types of transactions we are evaluating include partnerships, out-licensing deals, mergers, and other structures to access capital, and aim to leverage Seres' expertise and track record of successfully bringing a live biotherapeutic product to the market," said Thomas DesRosier and Marella Thorell, co-CEOs of Seres. "Our clinical data underscore the potential of SER-155 to transform care for allo-HSCT recipients and other high-risk patients vulnerable to bloodstream infections, an area of significant unmet need and commercial opportunity. Informed by constructive FDA feedback, we have submitted a protocol to the agency for a well-powered, placebo-controlled SER-155 Phase 2 study, which includes a planned interim analysis designed to enable an expedited readout. The FDA has continued to engage with the Company and has indicated they will provide feedback, which we expect will support finalizing the protocol."

**Recent Highlights** 

**SER-155 and Bloodstream Infection Prevention** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Seres' business development discussions are focused on supporting SER-155 clinical advancement. The Company is engaging with several parties regarding a range of deal structures including: partnerships, out-licensing deals, mergers,
and other structures to access capital, and which could potentially leverage Seres' live biotherapeutics expertise and experience successfully bringing a live biotherapeutic product from development through FDA approval.

------

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Based on prior US Food and Drug Administration (FDA) feedback, Seres has continued preparations for a SER-155 Phase 2 study that could provide a time and capital-efficient path to obtaining clinical results. In May 2025, the Company filed the SER-155 Phase 2 protocol with the
FDA and is anticipating FDA feedback, which is expected to support finalizing the protocol.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The SER-155 Phase 2 study is expected to enroll approximately 248
participants and incorporate an adaptive design and an interim data analysis when approximately half of the enrolled participants have reached the primary endpoint. The Company expects to obtain the interim clinical results within 12 months
following study initiation, which it believes will facilitate timely engagement with the FDA on the design of a Phase 3 study and inform development in adjacent medically vulnerable patient populations. The Company believes that positive results
from the Phase 2 study, if achieved, could enable advancement into a single Phase 3 trial to support registration.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• In May 2025, the Company presented new exploratory biomarker data from the SER-155 Phase 1b study in a poster session at the American Society of Clinical Oncology (ASCO) Annual Meeting held in Chicago. These data demonstrate the potential of SER-155 to promote immune reconstitution following allo-HSCT, by modulating homeostatic cytokines and peripheral T-cell expansion, and improve clinical outcomes in these
patients.

**Development of Biotherapeutics for the Treatment of Inflammatory and Immune Diseases** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The Company is collaborating with Memorial Sloan Kettering Cancer Center on an investigator-sponsored trial
(IST), now underway, to evaluate SER-155 in patients with immune checkpoint related enterocolitis (irEC).

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• In May 2025, Seres presented data at the Digestive Disease Week (DDW) conference describing a novel biomarker
that may predict a more robust treatment response in patients with ulcerative colitis who are administered a biotherapeutic product. The Company received a Poster of Distinction award in the Microbiome and Microbial Therapies subgroup. These
findings support the potential of live biotherapeutics as a novel treatment modality for gut-related inflammatory and immune diseases, suggesting that patient subpopulations well-suited for this approach may
be identifiable. This research has been supported by the Crohn's & Colitis Foundation.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Seres is exploring potential R&D partnerships to advance development of its investigational live
biotherapeutics in inflammatory and immune diseases, including ulcerative colitis and Crohn's disease.

**Recent Corporate Updates** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Seres received the $25 million installment payment from Nestlé Health Science (Nestlé) in July
2025, as expected, and concurrently paid Nestlé $1.4 million in employment-related obligations. The Company has completed the majority of Transition Service Agreement (TSA) activities related to its VOWST<sup>™</sup> asset sale to Nestlé .

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Thomas DesRosier and Marella Thorell were appointed co-Chief Executive
Officers, effective August 1, 2025. This followed the departure of our prior CEO, Eric Shaff, on July 31 2025, after a decade with the Company, to pursue a new professional opportunity. Mr. DesRosier and Ms. Thorell retain responsibilities
related to their roles as Chief Legal Officer and Chief Financial Officer, respectively. Mr. Shaff will continue to serve as a Director on the Seres Board.

------

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Effective August 5, 2025, Robert Rosiello, an Executive Partner at Flagship Pioneering, joined the board of

portfolio companies. He previously held senior roles at McKinsey & Company and served as EVP and CFO at Valeant. He currently serves on several boards, including Sana Biotechnology (Nasdaq: SANA), the Marine Biological Laboratory, and
Catholic Charities of New York.

**Financial Results** 

The Company has classified all historical operating results for the VOWST business within discontinued operations in the consolidated statements of operations for the comparative periods presented (three and six months ended June 30, 2024). There is no activity in the current period related to discontinued operations.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Seres reported a net loss from continuing operations of $19.9 million for the second quarter of 2025,
as compared to $26.2 million for the same period in 2024.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Research and development (R&D) expenses for the second quarter of 2025 were $12.9 million, compared
with $15.8 million for the second quarter of 2024. The decrease in R&D expenses was primarily driven by a decrease in expenses resulting from completion of the SER-155 Phase 1b study, lower
personnel and related expenses, and a decrease in platform investments.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• General and administrative (G&A) expenses for the second quarter of 2025 were $10.3 million,
compared with $13.1 million for the second quarter of 2024. The decrease in G&A expenses was primarily a result of lower personnel and related expenses, including IT-related expenses.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Manufacturing services expenses were $1.7 million for the second quarter of 2025. These costs relate to the
provision of manufacturing services under the TSA with Nestlé, which began in the fourth quarter of 2024. The reimbursement received from Nestlé related to these expenses is recognized in other income.

**Cash Runway** 

As of June 30, 2025, Seres had $45.4 million in cash and cash equivalents. Based on the Company's current cash position, the $25 million installment payment received from Nestlé in July 2025, VOWST transaction-related obligations, and current operating plans, the Company expects to fund operations into the first quarter of 2026. The Company has implemented and continues to evaluate cost reduction actions aimed at extending its cash runway.

**Conference Call Information** 

Seres' management will host a conference call today, August 6, 2025, 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 3641971. 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.

------

**About SER-155**

SER-155 is an investigational, oral, live biotherapeutic designed to decolonize gastrointestinal (GI) pathogens, improve epithelial barrier integrity, and induce immune homeostasis, to prevent bacterial bloodstream infections, including those that can harbor antimicrobial resistance (AMR), as well as other pathogen associated negative clinical outcomes, in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT).

SER-155 has been evaluated in a Phase 1b placebo-controlled study in patients undergoing allo-HSCT, which demonstrated a significant reduction in both bacterial bloodstream infections (BSIs) (77% relative risk reduction) and systemic antibiotic exposure, as well as lower incidence of febrile neutropenia. SER-155 has received Breakthrough Therapy designation for the reduction of bloodstream infections in adults undergoing allo-HCST and Fast Track designation for reducing the risk of infection and graft-versus-host disease in patients undergoing allo-HCST. The early development of the program was supported by Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator (CARB-X), a global non-profit partnership accelerating antibacterial products to address drug-resistant bacteria.

**About Seres Therapeutics**

Seres Therapeutics, Inc. (Nasdaq: MCRB) is a clinical-stage company focused on improving patient outcomes in medically vulnerable populations through novel live biotherapeutics. Seres led the successful development and approval of VOWST<sup>™</sup>, the first FDA-approved orally administered microbiome therapeutic, which was sold to Nestlé Health Science in September 2024. The Company is developing SER-155, which has received Breakthrough Therapy designation for the reduction of bloodstream infections in adults undergoing allo-HSCT and Fast Track designation for reducing the risk of infection and graft-versus-host disease in adults undergoing allo-HSCT, and which has demonstrated a significant reduction in bloodstream infections and related complications (as compared to placebo) in a Phase 1b clinical study in patients undergoing allo-HSCT. SER-155 and the Company's other pipeline programs are designed to target multiple disease-relevant pathways and are manufactured from standard clonal cell banks via cultivation, rather than from the donor-sourced production process used for VOWST. In addition to allo-HSCT, the Company intends to evaluate SER-155 and other cultivated live biotherapeutic candidates in other medically vulnerable patient populations including autologous-HSCT patients, cancer patients with neutropenia, CAR-T recipients, individuals with chronic liver disease, solid organ transplant recipients, as well as patients in the intensive care unit and long-term acute care facilities. For more information, visit www.serestherapeutics.com.

**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 timing and results of our clinical studies and data readouts; current or future product candidates and their potential benefits; clinical development plans and commercial opportunities; communications with, feedback from, or submissions to the FDA; operating plans, cost reduction actions, and our future cash runway; our ability to secure a strategic, R&D, or other partnership and/or generate or obtain additional capital, financing or other resources; our planned strategic focus; the anticipated timing of any of the foregoing; and other statements that 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) 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 limited operating history; (5) the expected payments from the VOSWT sale are subject to risks and uncertainties; (6) we may not be able to realize the anticipated benefits of the VOWST sale, and may face new challenges as a smaller, less diversified company; (7) we have in the past and may in the future receive notice of the failure to satisfy a continued listing rule from The Nasdaq Stock Market LLC; (8) our novel approach to therapeutic intervention; (9) our reliance on third parties to conduct our clinical trials and manufacture our product candidates; (10) our ability to achieve market acceptance necessary for commercial success; (11) the competition we will face; (12) our ability to protect our intellectual property; and (13) our ability to manage our recent CEO transition, to retain key personnel and to manage our growth. 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 7, 2025 and our Quarterly Report on Form 10-Q to be filed with the SEC on August 6, 2025, as well as 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)** 

---

| | | |
|:---|:---|:---|
|  | **June 30,<br>2025** | **December 31,<br>2024** |
|  **Assets** |  |  |
|  Current assets: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Cash and cash equivalents | $45379 | $30793 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Accounts receivable due from SPN - related party | 882 | 2068 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Prepaid expenses and other current assets (1) | 2424 | 5813 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total current assets | 48685 | 38674 |
|  Property and equipment, net | 9622 | 11534 |
|  Operating lease assets | 76794 | 80903 |
|  Restricted cash | 8668 | 8668 |
|  Other non-current assets | 31 | 31 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total assets | $143800 | $139810 |
|  **Liabilities and Stockholders' Equity** |  |  |
|  Current liabilities: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Accounts payable | $2200 | $4079 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Accrued expenses and other current liabilities | 5809 | 10719 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Accrued liabilities due to SPN - related party | 13453 | 17750 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Operating lease liabilities | 9478 | 8674 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total current liabilities | 30940 | 41222 |
|  Operating lease liabilities, net of current portion | 77956 | 82966 |
|  Other long-term liabilities | 1954 | 1838 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total liabilities | 110850 | 126026 |
|  Commitments and contingencies (Note 9) |  |  |
|  Stockholders' equity (deficit): |  |  |
|  Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2025 and December 31, 2024; no shares issued and outstanding at June 30, 2025 and December 31, 2024 |  |  |
|  Common stock, $0.001 par value; 360,000,000 shares authorized at June 30, 2025 and December 31, 2024; 8,754,482 and 8,650,227 shares issued and outstanding at June 30, 2025 and December 31, 2024, respectively | 9 | 9 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Additional paid-in capital | 998213 | 991874 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Accumulated other comprehensive loss |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Accumulated deficit | (965272) | (978099) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total stockholders' equity | 32950 | 13784 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total liabilities and stockholders' equity | $143800 | $139810 |

---

---

| | |
|:---|:---|
| <sup>[1]</sup> | Includes $279 as of June 30, 2025 and $2,683 as of December 31, 2024 of unbilled receivable from SPN (related party) related to certain costs of the transition services performed by the Company.  |

---

------

**SERES THERAPEUTICS, INC.** 

**CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS)** 

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

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Three Months Ended<br>June 30,** | **Three Months Ended<br>June 30,** | **Six Months Ended<br>June 30,** | **Six Months Ended<br>June 30,** |
|  | **2025** | **2024** | **2025** | **2024** |
|  Operating expenses: |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Research and development expenses | $12939 | $15806 | $24760 | 35300 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; General and administrative expenses | 10253 | 13065 | 22141 | 28009 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Manufacturing services | 1689 |  | 5216 |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total operating expenses | 24881 | 28871 | 52117 | 63309 |
|  Loss from operations | (24881) | (28871) | (52117) | (63309) |
|  Other income (expense): |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Gain on sale of VOWST Business | 185 |  | 52366 |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Interest income | 546 | 1230 | 1164 | 2878 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Interest expense |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Other income (2) | 4295 | 1445 | 11414 | 1332 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total other income, net | 5026 | 2675 | 64944 | 4210 |
|  Net income (loss) from continuing operations | $(19855) | $(26196) | $12827 | $(59099) |
|  Net (loss) from discontinued operations, net of tax | $— | $(6674) | $— | $(13904) |
|  Net income (loss) and comprehensive income (loss) | $(19855) | $(32870) | $12827 | $(73003) |
|  Net income (loss) from continuing operations per share attributable to common stockholders - basic | $(2.27) | $(3.46) | $1.47 | $(7.94) |
|  Net (loss) from discontinued operations per share attributable to common stockholders - basic | $— | $(0.88) | $— | $(1.87) |
|  Net income (loss) per share attributable to common stockholders - basic | $(2.27) | $(4.34) | $1.47 | $(9.81) |
|  Net income (loss) from continuing operations per share attributable to common stockholders - diluted | $(2.27) | $(3.46) | $1.47 | $(7.94) |
|  Net (loss) from discontinued operations per share attributable to common stockholders - diluted | $— | $(0.88) | $— | $(1.87) |
|  Net income (loss) per share attributable to common stockholders - diluted | $(2.27) | $(4.34) | $1.47 | $(9.81) |
|  Weighted average common shares outstanding - basic | 8743733 | 7575620 | 8723589 | 7440323 |
|  Weighted average common shares outstanding - diluted | 8743733 | 7575620 | 8732176 | 7440323 |

---

---

| | |
|:---|:---|
| <sup>[2]</sup> | Includes $3,490 and $9,799 for the three and six months ended June 30, 2025 related to reimbursement received from SPN (related party) for transition services provided by the Company.  |

---

**Investor and Media Contact:**

IR@serestherapeutics.com

Carlo Tanzi, Ph.D.

Kendall Investor Relations

ctanzi@kendallir.com

## Exhibit 99.2

![Slide 1](g930624ex99_2s1g1.jpg)

Seres Therapeutics Investor Presentation August 2025 Exhibit 99.2

------

![Slide 2](g930624ex99_2s2g1.jpg)

Disclaimers 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 timing and results of our clinical studies and data readouts; current or future products or product candidates and their potential benefits; our clinical development plans; communications with, feedback from, or submissions to the FDA; future product candidates; our ability to secure a strategic, R&D or other partnership and/or generate additional capital, financing, or other resources; the potential market and commercial opportunity for SER-155 and other product candidates, if approved; operating plans, cost reductions actions, and our future cash runway, including potential payments due from Nestlé related to the VOWST sale; our planned strategic focus; the timing of any of the foregoing; and other statements that 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) 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 limited operating history; (5) the expected payments from the VOSWT sale are subject to risks and uncertainties; (6) we may not be able to realize the anticipated benefits of the VOWST sale, and may face new challenges as a smaller, less diversified company; (7) we have in the past and may in the future receive notice of the failure to satisfy a continued listing rule from The Nasdaq Stock Market LLC; (8) our novel approach to therapeutic intervention; (9) our reliance on third parties to conduct our clinical trials and manufacture our product candidates; (10) our ability to achieve market acceptance necessary for commercial success; (11) the competition we will face; (12) our ability to protect our intellectual property; and (13) our ability to manage our recent CEO transition, to retain key personnel and to manage our growth. 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 7, 2025 and our Quarterly Report on Form 10-Q to be filed with the SEC on August 6, 2025, as well as 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 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. Seres Therapeutics, Inc.© 2025

------

![Slide 3](g930624ex99_2s3g1.jpg)

Transforming patient outcomes using proprietary consortia of live biotherapeutics Strong Foundation Validated platform highlighted by VOWST® FDA approval as first ever oral microbiome therapy with outstanding clinical results VOWST asset sale strengthened balance sheet and streamlined organization Cash into Q1 2026 Positive SER-155 Phase 1b Data in Allo-HSCT 77% relative risk reduction for bloodstream infections Well tolerated safety profile Exploratory biomarker data reinforce SER-155 MOA Breakthrough Designation Constructive FDA feedback on Phase 2 study; protocol submitted in Q2 2025 Blockbuster SER-155 Opportunity Initial SER-155 development in allo-HSCT Potential to initiate multiple clinical trials for additional indications Multi-billion net sales opportunity across indications (e.g., autologous-HSCT, blood cancers, CAR-T recipients) Investigator-sponsored trial in immune-related enterocolitis Expansive Platform Potential Systemic inflammation and immune homeostasis biomarker data support the potential in inflammatory and immune diseases, such as IBD (e.g., ulcerative colitis and Crohn's disease) SER-147 designed to prevent infections in chronic liver disease Seres Therapeutics, Inc.© 2025 Engaging with multiple parties regarding various deal structures, including potential business development and partnerships, intended to secure capital and other resources to enable the clinical advancement of SER-155 and additional live biotherapeutic product candidates

------

![Slide 4](g930624ex99_2s4g1.jpg)

Validated therapeutic modality and platform: Seres pioneered the development and FDA approval of VOWST as the first-ever oral live microbiome therapeutic FDA approved (April 2023) to prevent the recurrence of C. difficile infection in adults Approximately 88% sustained clinical response rate (C. diff. recurrence, at up to 8 weeks) DRAMATIC CLINICAL BENEFIT – Preventing infection recurrence Source: Feuerstadt P et al. N Engl J Med. 2022;386(3):220-229 VOWST asset sale (completed September 2024) provided capital to support pipeline advancement and resulted in a more streamlined, focused organization Seres Therapeutics, Inc.© 2025

------

![Slide 5](g930624ex99_2s5g1.jpg)

VOWST asset sale completed September 30, 2024: transformational for Seres – provides resources to support SER-155 advancement KEY FINANCIAL TERMS VOWST asset purchase agreement provided infusion of capital and to SER-155 development Asset sale extended operational runway Retired debt and other obligations Majority of transition activities complete as of Q2 2025; manufacturing services through end of 2025 $100M upfront payment to Seres, less ~$20M in net obligations due to an affiliate of SPN\* $15M equity investment by SPN at closing $60M prepaid sales-based milestone at closing $50M received in January 2025 $25M (offset by $1.4M in employment-related payment) received in July 2025 $275M in potential future sales-based milestone payments (subject to reductions for interest on prepaid milestone payment) Transaction results in a more streamlined, focused Seres organization and lower cash burn rate \*SPN: Société des Produits Nestlé S.A. Seres Therapeutics, Inc.© 2025

------

![Slide 6](g930624ex99_2s6g1.jpg)

The gut microbiome has substantial untapped therapeutic potential to both prevent and treat diseases The genetic content of the microbes living within and on your body is at least 100-fold greater than that contained in the human genome Sources: Ley et al. (2006) Cell; Qin et al. (2010) Nature Seres Therapeutics, Inc.© 2025

------

![Slide 7](g930624ex99_2s7g1.jpg)

Disrupted gastrointestinal microbiome is mechanistically linked to infections and disease Impacted Biology & Disease Relevance Increased pathogen abundance, in combination with impaired barrier integrity and decreased immune function… …enables bacterial and antigen translocation leading to infections & inflammation Disrupted & Disease Susceptible Not Disrupted Lost epithelial barrier & mucosal integrity Unfavorable immune responses Pathogen or "undesirable" microbe abundance Seres Therapeutics, Inc.© 2025

------

![Slide 8](g930624ex99_2s8g1.jpg)

Consortia of live commensal bacteria can be used as therapeutics Change in microbiome function Bile acids Short-chain fatty acids Tryptophan metabolites Other Restructure microbiome composition Engraftment of drug strains Disrupted Microbiome with functional deficiencies (Disease susceptible) Change in host function Consortia of bacterial strains Optimized to target multiple disease-relevant pathways Live Biotherapeutics PK PD Seres Therapeutics, Inc.© 2025

------

![Slide 9](g930624ex99_2s9g1.jpg)

Seres' biotherapeutics and pipeline candidates are expected to have well tolerated safety profile, reducing development risk Sources: Nanayakkara et al, CA Cancer J Clin 2021; Penack et al, Blood Adv 2020; Zheng et al, Infect Dis Ther 2021 Based on GI bacteria naturally found in healthy humans, and not associated with disease VOWST product profile includes well tolerated safety without drug-related serious adverse events Well tolerated safety profile in multiple clinical trials and patient populations, including medically vulnerable allo-HSCT recipients Safety profile has potential to mitigate a primary cause of drug development failure Seres Therapeutics, Inc.© 2025

------

![Slide 10](g930624ex99_2s10g1.jpg)

Seres' initial focus is preventing infections in allo-HSCT; potential is broad Allo-HSCT Survival by microbiome diversity Lower microbiome diversity post allo-HSCT is associated with increased blood stream infections and decreased overall survival Autologous HSCT Survival by microbiome diversity Lower microbiome diversity post auto-HSCT is associated with worse overall and progression-free survival Chronic Liver Disease Microbiome diversity decreases with disease severity and is associated with increased risk of infection & death Sources: Peled, et al, NEJM 2020; Khan et al, Blood 2021; Bajaj et al, Clin Gastroenterol Hepatol 2019; Odenwald, et al. Nature Micro. 2023 Common biology across vulnerable populations: pathogen domination in the GI microbiome, loss of epithelial barrier integrity, impacted immune function Survival by microbiome diversity Seres Therapeutics, Inc.© 2025

------

![Slide 11](g930624ex99_2s11g1.jpg)

Near-term focus on SER-155 as anchor biotherapeutic program; constructive FDA engagement on path forward in addition to Breakthrough and Fast Track designations Program Lead Indication & Development Stage Therapeutic Objectives Potential Additional Indications SER-155 Allogeneic HSCT: Phase 1b Cohort 2 (placebo controlled) data announced Sept. '24 and exploratory biomarker data in Q1 '25 Reduce incidence of serious bacterial infections (e.g., BSIs), febrile neutropenia, and GvHD Autologous HSCT Blood cancers CAR-T Investigator sponsored study in Immune checkpoint related enterocolitis (irEC) started SER-147 Chronic liver disease: IND-enabling activities Reduce incidence of serious bacterial infections (e.g., SBP, BSIs) and related complications Solid organ transplant ICU patients Long-term care patients provides clinical proof of concept Reduces risk of recurrent C. diff infections Well tolerated safety profile Phase 2 study protocol submitted to FDA in May 2025; anticipating further FDA feedback which is expected to support finalizing protocol BSI: bloodstream infection; SBP: spontaneous bacterial peritonitis Seres Therapeutics, Inc.© 2025

------

![Slide 12](g930624ex99_2s12g1.jpg)

Allo-HSCT regimen can result in infectious consequences and increased mortality Sources: CIBMTR 2023 US summary slides; Passweg et al BMT 2025; Penack et al, Blood Adv 2020; Khan et al, Blood 2021; Peled et al, NEJM 2020; Stein-Thoeringer et al, Science 2019; Bleakley & Riddell, Nat Rev Cancer 2004 Seres Therapeutics, Inc.© 2025 Only ~60% survival 3 years post-transplant in US and EU Significant immune compromise ~10% transplant mortality for adults in first 100 days post-transplant Infections are a leading cause of death Gut microbiome disruption frequently observed globally (US, Germany, Japan) Allo-HSCT treatment regimen -14 0 +100 Days Conditioning Immunosuppression Chemotherapy Anti-infectives Increased risk of infection, GvHD Allo-HSCT infusion Extensive GI microbiome disruption Treatment consequences

------

![Slide 13](g930624ex99_2s13g1.jpg)

Bloodstream infections (BSIs) are a leading cause of death post-transplant and are increasing in incidence BSI risk increasing due to recent adoption of post-transplant cyclophosphamide (PTCy) for GvHD prophylaxis BSI prevalence high despite standard of care use of antibacterial prophylaxis ~50% of infections are gut-seeded 50-80% febrile neutropenia incidence Incidence Sources: Gill et al, Microorganisms 2023; Sava et al, Bone Marrow Transplantation 2022; Carreira et al, Transplant Cell Ther 2022; Youssef et al, Pediatric Transplantation 2020; Song et al, Infect Drug Resist 2023; Bolaños-Meade J et al, NEJM 2023; Salas et al, Transplant Cell Ther 2024; Rearigh et al, Annals of Hematology 2020; CIBMTR 2023 US summary slides; Perales et al Biol Blood Marrow Transplant 2017; Taplitz et al, J Clin Oncol 2018; 2024 Seres physician market research Bacterial BSI in first 30 days post-HSCT Salas et al 2024 Impact Infection is leading cause of death in first 100 days post-HSCT for adults ~7.5% mortality rate from bloodstream infections Complications including infection associated with longer hospital stay and ICU utilization, driving substantial cost increase PTCy Non-PTCy Seres Therapeutics, Inc.© 2025

------

![Slide 14](g930624ex99_2s14g1.jpg)

Standards of care to prevent bloodstream infections in allo-HSCT patients are poor and decreasing in efficacy \* ASCO: American Society of Clinical Oncology; IDSA; Infectious Diseases Society of America; EBMT: formerly known as the European Society for Blood and Marrow Transplantation; PTCy: post-transplant cyclophosphamide Sources: Taplitz et al, J Clin Oncol 2018; EBMT 2022 report; Neuerberg et al Transplant Cell Ther 2024; Bolaños-Meade et al, NEJM 2023 Joint ASCO\* and IDSA recommendation Fluoroquinolones (FQ) recommended for antibacterial prophylaxis Prophylaxis recommended during window of expected neutropenia EBMT guidelines and Infectious Disease Working Party recommendations 2022 Workshop recommends move to "targeted" antibacterial prophylaxis Multiple analyses suggest reduced infections from antibacterial prophylaxis but no overall survival benefit Trends High BSI rate happening despite broad FQ prophylaxis in the US Prophylaxis efficacy decreasing as bacteria become resistant to antibiotics PTCy adoption for GvHD prophylaxis is increasing BSI rates Seres Therapeutics, Inc.© 2025

------

![Slide 15](g930624ex99_2s15g1.jpg)

SER-155 Phase 1b study evaluated safety, pharmacology, and efficacy in adult allo-HSCT recipients SER-155 COHORT 1 Open-label (n=15 enrolled) COHORT 2 Placebo-controlled 1:1 (n=45 enrolled) SER-155 Placebo results reported May 2023 results announced Sept. 2024 Primary Endpoints: Safety and tolerability SER-155 bacterial strain engraftment Key Secondary Endpoints through HSCT Day 100: Incidence of bloodstream infections (BSI), GI infections, and acute GvHD ≥ Grade 2 Incidence and duration of febrile neutropenia Bacterial pathogen abundance Seres Therapeutics, Inc.© 2025

------

![Slide 16](g930624ex99_2s16g1.jpg)

SER-155 Safety: SER-155 was generally well tolerated with no treatment-related SAEs Treatment-emergent adverse events (TEAEs) All but one subject in the placebo arm experienced at least 1 TEAE Most common for SER-155 treated subjects (≥50% and with Δ ≥5% greater than placebo): diarrhea (86% vs. 74% placebo), nausea (62% vs. 53% placebo) 1/40 (3%) subject experienced a TEAE leading to treatment discontinuation (active = 0; placebo = 1) 3/40 (8%) subjects experienced a TEAE leading to study discontinuation (active = 1; placebo = 2) Serious adverse events (SAEs) 19/40 (48%) subjects experienced an SAE: 11/21 (52%) SER-155-treated subjects vs. 8/19 (42%) placebo-treated subjects; none considered related to SER-155 (no SUSARs) Most common SAE SOC: infections & infestations (24% active vs. 37% placebo) 3 deaths prior to Day 100 (active = 1; placebo = 2), 1 death after Day 100 (active), none considered related to SER-155 Adverse events of special interest (AESIs) AESIs (bloodstream infections, GI infection, invasive infection): 14/40 (35%) subjects Rates of AESIs were lower in SER-155 arm vs placebo arm (29% vs 42% respectively) No SER-155 species were identified in culture from any subject Seres Therapeutics, Inc.© 2025

------

![Slide 17](g930624ex99_2s17g1.jpg)

SER-155 Efficacy: SER-155 associated with 77% relative risk reduction in bacterial BSIs and reduction in systemic antibiotic exposure Bloodstream infections Significant decrease in bacterial bloodstream infections in SER-155-treated subjects vs. placebo with 77% relative risk reduction Numerically lower incidence rate of febrile neutropenia in SER-155-treated subjects vs. placebo Febrile neutropenia Antibiotic exposures Significantly lower mean cumulative exposure (days) and exposure rate to systemic antibacterials / antimycotics for SER-155-treated subjects vs. placebo \* CDI: C. difficile infection Seres Therapeutics, Inc.© 2025

------

![Slide 18](g930624ex99_2s18g1.jpg)

Bloodstream infections from HSCT Day 0 to Day 100: Lower incidence in SER-155 treated subjects vs. placebo Bloodstream infections from Day 0 to Day 100 (# patients) SER-155 n=20 n (%) Placebo n=14 n (%) Subjects with confirmed BSI 2 (10.0%) 6 (42.9%) 95% confidence interval (1.2, 31.7) (17.7, 71.1) CI: 95% 2-sided Clopper-Pearson confidence interval of incidence is applied Odds ratio: for incidence between treatment groups (SER-155 and placebo) with 95% 2-sided confidence interval and the corresponding p-value calculated based on the Fisher's Exact test Odds ratio 0.15 95% confidence interval (0.01, 1.13) p-value 0.0423 mITT-1 population Organisms in SER-155 patients: Finegoldia magna; E. coli/Strep mitis Organisms in placebo patients: E.coli; Enterococcus faecium/staph haemolyticus/Candida krusei; Staph aureus; Staph haemolyticus; Pseudomonas aeruginosa; E coli Seres Therapeutics, Inc.© 2025

------

![Slide 19](g930624ex99_2s19g1.jpg)

Cumulative exposure to systemic antibacterials / antimycotics through HSCT Day 100: Lower incidence in SER-155 treated subjects vs. placebo Cumulative Antibacterial or Antimycotic Exposure (HSCT Days) SER-155 n=20 n (SD) Placebo n=14 n (SD) Mean (SD) 9.2 (5.44) 21.1 (20.31) Median 9.0 14.0 Min, Max 0, 19 0, 74 Cumulative exposure is the sum of all days a subject received systemic antibacterials and/or antimycotics between HSCT Day 0 through Day 100; counting once per day regardless of number of agents taken 95% confidence interval and p-value based on independent samples t-test of the difference in mean days between SER-155 and placebo Mean Difference (95% CI) -11.9 (-23.85, -0.04) p-value 0.0494 mITT-1 population Seres Therapeutics, Inc.© 2025

------

![Slide 20](g930624ex99_2s20g1.jpg)

Cumulative exposure rate to systemic antibacterials / antimycotics through HSCT Day 100: Lower incidence in SER-155 treated subjects vs. placebo Cumulative Antibacterial or Antimycotic Exposure Rate SER-155 n=20 Rate (SD) Placebo n=14 Rate (SD) Mean (SD) 0.090 (0.0530) 0.305 (0.2898) Median 0.089 0.244 Min, Max 0.00, 0.18 0.00, 0.90 Cumulative exposure rate is calculated as the sum of all days a subject received systemic antibacterials and/or antimycotics on or after HSCT Day 0 (counting once per day, regardless of number of antibacterial/antimycotic medications taken in a day) through HSCT Day 100 over the total number of days a subject was on the study from HSCT Day 0 to the earliest of EOS, or HSCT Day 100 95% confidence interval and p-value are based on independent samples t-test of the difference in mean days or mean rate of cumulative exposure between SER-155 and Placebo Mean Difference (95% CI) -0.2 (-0.38, -0.05) p-value 0.0163 mITT-1 population Seres Therapeutics, Inc.© 2025

------

![Slide 21](g930624ex99_2s21g1.jpg)

Measurements on Ph1b clinical study Preclinical Optimization SER-155 Pharmacodynamics: the Phase 1b study included multiple measures of drug pharmacodynamics which provide support for the intended biological activity SER-155 Mechanism of Action Targets Concentration of fecal albumin in subject stool, reflecting barrier damage and leakage of serum albumin into the GI tract Repair & Protect Intestinal Epithelial Barrier Integrity Concentrations of plasma cytokines, chemokines and signaling molecules reflecting GI inflammation, systemic inflammation, and immune homeostasis Modulate/Regulate Immune Responses & Function Genomic measurements of pathogen abundance in gastrointestinal tract, including domination by pathogenic bacteria Inhibit Pathogens or "Undesirable" Microbes Clinical Support for MoA Seres Therapeutics, Inc.© 2025

------

![Slide 22](g930624ex99_2s22g1.jpg)

SER-155 Pharmacodynamics (pathogen domination): prevalence in SER-155 Cohort 2 was substantially lower relative to Historical Control Cohort Pathogen domination (i.e., relative abundance in the GI ≥30%) has been associated with risk of BSIs and other negative clinical outcomes1, 2 Observed pathogen domination events were low in both the placebo and SER-155 arms with no significant differences observed The ability to detect pathogen domination in the placebo arm was constrained due to the imbalance in the number of available stool samples between the arms. Pathogen domination was substantially lower in SER-155 Cohort 2 compared to Historical Control Cohort3 1 - Peled et al, NEJM 2020; Stein-Thoeringer et al, Science 2019; Kusakabe et al, BBMT 2020 2 - Bacteria in the families: ESKAPE (Enterococcaceae, Enterobacteriaceae & Staphylococcaceae) & Streptococcaceae; domination defined as ≥30% relative abundance in the GI 3 - Subjects that are sampled at similar time points as SER-155 Phase 1b subjects; microbiome data produced using same protocols as SER-155 Phase 1b subjects Seres Therapeutics, Inc.© 2025

------

![Slide 23](g930624ex99_2s23g1.jpg)

Clinical: Epithelial barrier exploratory translational biomarker results support intended mechanisms of action and clinical safety and efficacy results Box plots (SER-155 = blue; Placebo = grey; Healthy Control = green) represent the 25th and 75th percentiles of the inter-quartile range (IQR) of distribution with median value indicated by horizontal marker. The vertical whiskers cover all data within 1.5 \* IQR. Green dashed line corresponds to 75th percentile of IQR of fecal albumin concentrations measured in healthy control population; LLOD for assay = 3125 ng/mL. P-values reported for general linear model (GLM) comparing arms; results consistent if baseline concentrations are included in the model. Repair & Protect Intestinal Epithelial Barrier Integrity Following SER-155 treatment course 1 ("post-155 T1"), fecal albumin levels were significantly lower in SER-155 compared to placebo At the post-155 T1 timepoint, fecal albumin levels in placebo were significantly higher than levels observed in healthy volunteers, consistent with barrier damage induced by HCT conditioning. Fecal albumin levels remained low in SER-155 subjects and similar to healthy volunteers throughout the peri-transplant period suggesting barrier protection. p = 0.0006 Baseline Post- SER-155 HCT Day 0 Healthy Neutrophil engraftment N= Fecal Albumin (ng/ML) Seres Therapeutics, Inc.© 2025

------

![Slide 24](g930624ex99_2s24g1.jpg)

Clinical: Anti-inflammatory translational biomarker results support intended mechanisms of action and clinical safety and efficacy results "155 < PBO" indicates time points with lower biomarker concentrations in SER-155 arm compared to placebo. Blue shaded cells indicate time points with statistical significance based on a generalized linear model (GLM), with threshold noted. P-values reported for GLM to evaluate impact of treatment. "155 < PBO" result shown for time points that are directionally consistent if baseline concentrations are included in the model, though significance may have shifted. Modulate / Regulate Immune Responses and Function Biomarker Post-155 T1 HCT Day 0 Neutrophil recovery IFN-γ 155 < PBO p<0.1 155 < PBO p<0.05 TNF-α 155 < PBO p<0.1 IL-17 155 < PBO p<0.05 155 < PBO p<0.05 155 < PBO IL-8 155 < PBO 155 < PBO In the peri-transplant period, treatment with SER-155 was associated with lower plasma concentrations of several pro-inflammatory cytokines relative to placebo including: IFN-g, TNF-a, IL-17 & IL-8. Seres Therapeutics, Inc.© 2025

------

![Slide 25](g930624ex99_2s25g1.jpg)

US HCPs seek significant reduction of infection risk without compromising patient safety and would incorporate such a therapeutic into standard of care Efficacy Safety Health economics Reduce incidence of bloodstream infections: target 20% BSI rate vs. current 40% rate Reduce systemic antibiotic use that is contributing to rising resistance Reduce incidence of febrile neutropenia: target 60% FN rate vs. current 80% rate No major adverse event signals Expect translation to fewer deaths in the active study arm SER-155 Phase 1b data suggest potential to deliver this profile in a pivotal study Shorten hospital stay, reduce readmissions & reduce ICU utilization Source: Seres primary market research 2024 Profile of SER-155 Seres Therapeutics, Inc.© 2025

------

![Slide 26](g930624ex99_2s26g1.jpg)

HCPs see SER-155 as a potentially transformative means to eliminate complications that get in the way of achieving transplant success Primary Value Driver for SER-155 Reducing the risk of HSCT-related complications, thus ensuring successful engraftment and long-term health of the patient A relative risk reduction of 50% in BSIs is seen as "transformative" and would support broad inclusion in standard protocols for allo-HSCT patients Health Care Providers Streamlines the transplant process so they can spend more time treating the patient's underlying conditions and less time dealing with potential morbidities Patients One less thing to worry about for patients already dealing with a lot; additional financial and QoL benefits due to shortened hospital stays Healthcare System Reduced healthcare costs due to shorter hospital stays, fewer ICU visits, fewer antibiotic days and lower incidence of severe negative outcomes "This would probably be standard of care. It would be all eligible patients minus those who cannot tolerate it or are allergic." " " " The benefit would be massive because people die from these infections and so preventing them, the biggest benefit is mortality. The rest of the stuff with ICU admits and sepsis protocols and all…I think some of that also gets averted. That would be huge." Source: Seres primary market research 2024 Seres Therapeutics, Inc.© 2025

------

![Slide 27](g930624ex99_2s27g1.jpg)

US payers confirm high unmet clinical need for infection prophylaxis in allo-HSCT recipients and robust profile of SER-155 High clinical burden and unmet need High perceived clinical burden of BSIs within the allo-HSCT patient population is driven by high frequency of occurrences and poor associated outcomes Lack of an efficacious prophylactic therapy that successfully limits incidence of BSIs is considered a key unmet need and current driver of clinical burden Top unaided clinical concerns raised by payers include risk of febrile neutropenia, sepsis, and antibiotic-resistant infection Profile of SER-155 positively received Proposed risk reduction of BSIs and related endpoints were seen as clinically meaningful and supportive of value proposition "The reductions in primary and secondary endpoints are encouraging and brings hope that you are going to escape this risky scary complication of cancer therapy." Site of dispensing drives reimbursement pathway Oral administration is viewed as convenient by payers, with most expecting coverage under outpatient pharmacy benefit given oral administration likely outside of the hospital setting LOW HIGH Source: Q4 2024 US market research with sample including national and regional health plans + PBMs representing ~128M covered lives Clinical Burden Rating Seres Therapeutics, Inc.© 2025

------

![Slide 28](g930624ex99_2s28g1.jpg)

EU KOLs supportive of SER-155 Phase 1b results; eager to participate in Phase 2 clinical trial AML: acute myelogenous leukemia. BSI: Blood stream infections. HCT: hematopoietic cell transplantation. MDRO: multi-drug resistant organism. PTCy: post-transplant cyclophosphamide Ω EU KOL feedback on SER-155 at EBMT congress KOL feedback (Based on 14 KOL meetings) General:High-level awareness of Seres and SER-155 prior to Ph 1 presentations EU KOLs view BSIs as serious problem in HCT In southern EU countries, high rates of MDRO colonization is a significant risk factor for life-threatening and fatal BSI outcomes AML noted as an expansion opportunity for SER-155 Variable use of PTCy- and antibiotic-prophylaxis across EU unlike US Phase 1:Wide acceptance, enthusiasm of SER-155 clinical safety & efficacy results Phase 2:Strong support of primary endpoint being BSI, 30 days Eagerness to participate in Ph 2 trial; no competing trials in 2026 "Congratulations on the tremendous progress with your transformative microbiome intervention and the encouraging interaction with the FDA" ���� KOL "High interest, attractive findings, also economic benefit" ���� KOL "From our clinical point of view, we would have lots of patients for 155" (noted high number of MDROs at clinical site). ���� KOL "This work is very important; must restore GI tract" ���� KOL "These results are very encouraging" ���� KOL �������������������� Seres Therapeutics, Inc.© 2025

------

![Slide 29](g930624ex99_2s29g1.jpg)

Viral prophylaxis provides precedent in medically vulnerable patients Prevymis - increasingly used for viral infection prophylaxis (e.g., allo-HSCT and solid organ transplant populations) $785M '24 WW sales (~30% growth over '23) Reduces CMV infection in allo-HSCT recipients Lowers mortality rate Overall cost of allo-HSCT is high (~$400K US year 1 allo-HSCT costs) Transplant-related complications (e.g., infections) raise cost by ~$180K Infections result in longer hospital stays, readmissions, increased ICU utilization Sources: CMS.gov; Broder et al, Am Drug Health Benefits 2017; Perales et al, Biol Blood Marrow Transplant 2017; Merck SEC filings Seres Therapeutics, Inc.© 2025

------

![Slide 30](g930624ex99_2s30g1.jpg)

SER-155 has blockbuster commercial potential, driven by a robust SER-155 profile and substantial unmet needs in allo-HSCT and additional groups Sources: CIBMTR; HRSA; Passweg et al, BMT 2021; IQVIA; Broder et al, Am Drug Health Benefits 2017; Perales et al, Biol Blood Marrow Transplant 2017 CMS.gov; Merck SEC filings High unmet need to prevent frequent and serious infections ~40K annual transplants worldwide; 3% annual growth from aging population and transplant success rates Costly procedure (~$400K US year 1 allo-HSCT per patient cost) with high incremental costs of infections (incremental ~$180K/patient) SER-155 has potentially "transformational" profile with robust efficacy and safety Highly concentrated universe of transplant centers conducting stem cell transplant procedures allows for an efficient commercial model with rapid education on new standard of care Seres Therapeutics, Inc.© 2025

------

![Slide 31](g930624ex99_2s31g1.jpg)

Indication expansion: potential 10x addressable population US annual diagnoses or transplants Unmet needs addressed by SER-155 Allo-HSCT ~9,300 Prevent mortality and cost of post-transaction infections Autologous HSCT ~13,500 Prevent mortality and costs of post-transplant infections Broader leukemia & lymphoma population\* ~87,000 initial focus Reduce morbidity, mortality, and cost of infections and febrile neutropenia from chemotherapy \*Includes acute myeloid leukemia, multiple myeloma, and aggressive B cell non-Hodgkin lymphomas (diffuse large B-cell lymphoma, mantle cell, Burkitt's lymphoma) Sources: CIBMTR, US NCI SEER, Thandra et al 2021 report of WHO data, Niederwieser et al Haematologica 2022; WHO Global Cancer Observatory; American Cancer Society WW annual diagnoses or transplants ~40,000 ~60,000 ~500,000 Seres Therapeutics, Inc.© 2025

------

![Slide 32](g930624ex99_2s32g1.jpg)

Accelerating SER-155 clinical development based on positive Phase 1b outcomes Engaging with multiple parties regarding various deal structures to enable SER-155 clinical advancement in allo-HSCT and expand to multiple target populations Constructive engagement with FDA on advancement of SER-155 allo-HSCT program Received Breakthrough Therapy designation in December 2024 Submitted Phase 2 procotol to FDA in Q2; study aims to enroll 248 patients and incorporates adaptive design Phase 2 expected to incorporate interim data analysis which is anticipated within 12 months of study start; commencement of Phase 2 is funding dependent Intend to evaluate SER-155 in additional patient populations with high risk of serious bacterial infections Seres Therapeutics, Inc.© 2025 Memorial Sloan Kettering initiated IST to evaluate SER-155 for treatment of immunotherapy-related enterocolitis \*IST: investigator-sponsored trial

------

![Slide 33](g930624ex99_2s33g1.jpg)

SER-147 developed to prevent infections in chronic liver disease patients Substantial unmet need Promising preclinical data Sources: GBD 2017 Cirrhosis Collaborators, Lancet Gastroenterology & Hepatology 2020; United Nations world population data; Trebicka et al, J Hepatol 2020; Seres preclinical data from 2023 IDWeek 0.5M 2.1M ~50% SER-147 is an investigational live oral biotherapeutic designed to reduce pathogens causing gut-seeded SBP and BSIs in liver disease patients Declining E. coli titers experience bacterial infections in a 6 month period ~20-25% of infections are spontaneous bacterial peritonitis (SBP) and bloodstream infections likely to be gut-seeded Example: 1-3 log reduction of E. coli in in vitro models, plus reduction of other pathogens Seres Therapeutics, Inc.© 2025

------

![Slide 34](g930624ex99_2s34g1.jpg)

SER-603 designed to target inflammatory drivers of Inflammatory Bowel Disease (IBD) that current standards of care cannot Seres Therapeutics, Inc.© 2025 IBD is a mucosal barrier-immune disease Seres IBD Program Sources: Seres data on file Inflammatory microbiome Overabundance of pathogenic and inflammatory bacteria Loss of GI barrier integrity Barrier damage allows translocation of inflammatory bacteria and molecules Inflammatory immune responses Induce inflammatory responses in APCs and CD4+ T cells Nominated & validated novel, microbial-linked biomarkers that are predictive of response to current IBD therapies Demonstrated in preclinical models that SER-603, a novel cultivated LBP, can target all three drivers of disease without immunosuppression as a monotherapy and can improve response to advanced therapies in combination Supported by Crohn's & Colitis Foundation IBD Ventures award Actively engaged with potential partners to advance program SER-603 targets upstream of current IBD therapies and without immune suppression

------

![Slide 35](g930624ex99_2s35g1.jpg)

Manufacturing platform delivers defined consortia in oral formulation using cost-effective production Novel formulations enabling consistent drug product composition, drug stability for distribution, and targeted drug delivery Quality systems to ensure product quality and stability, extending prior regulatory successes, including developing product release specifications with the FDA Highly intensive strain bioprocessing leveraging flexible, single-use manufacturing technology for cost-effective production Strain isolation and characterization pipeline to rapidly identify cGMP-suitable medium components Seres Therapeutics, Inc.© 2025

------

![Slide 36](g930624ex99_2s36g1.jpg)

Maximizing opportunity of live biotherapeutics going forward SER-155 Bloodstream infections in Allo-HSCT: Engaged with FDA; constructive feedback on SER-155 development strategy; received Breakthrough Therapy designation Evaluate in additional cancer treatment populations w/ high risk of serious bacterial infections Investigator-sponsored trial treating immune checkpoint-related enterocolitis started Prevent life-threatening bacterial infections, including antimicrobial resistant infections in additional populations SER-603 to treat immune-related diseases (e.g., IBD, UC, Crohn's) Additional Opportunities SER-147 Infections in Chronic liver disease: IND enabling activities Indication expansion (e.g., radiation enteritis, ICU and long-term care patients, organ transplant) rCDI: Proven clinical and regulatory success; asset sale to Nestlé; Seres eligible for future milestones VOWST Seres Therapeutics, Inc.© 2025

------

![Slide 37](g930624ex99_2s37g1.jpg)

Summary and path forward SER-155 Phase 1b placebo-controlled clinical results promising and Phase 2 planning Constructive FDA engagement; Phase 2 study protocol submitted to FDA in May 2025; Commencement of Phase 2 is funding dependent Administration associated with 77% relative risk reduction for BSIs, significant reduction in systemic antibiotic exposure and lower incidence of febrile neutropenia vs placebo Exploratory biomarker data support SER-155 MOA and potential role for Seres' platform to provide clinical benefit to patients with inflammatory & immune diseases (e.g., UC & Crohn's disease) Capital Strategy & Financial position Engaging with multiple parties regarding various deal structures, including potential business development and partnerships, intended to secure capital and other resources to enable the clinical advancement of SER-155 and additional live biotherapeutic product candidates ~$45.4M in cash/cash equivalents at June 30, 2025; cash runway projected into Q1 2026 VOWST asset sale closed in Sept 2024; $50M received in January 2025 and $25M received in July 2025 (offset by ~$1.4M in employment-related payments) + $275M potential future milestones Developing a pipeline of novel live biotherapeutics in areas with large commercial potential SER-155 Phase 1b placebo-controlled clinical efficacy data support Seres' strategy Pipeline aims to bring transformative medicines to a wider set of patients, led by SER-155 VOWST approval validates using live biotherapeutics to prevent life-threatening infections Memorial Sloan Kettering initiated IST for treatment of immunotherapy-related enterocolitis (irEC) Seres Therapeutics, Inc.© 2025