Seres Therapeutics posts $16.3M net loss in Q3 2026
Available cash resources, including a $12.5 million October payment, are projected to fund operations through the first quarter of 2027.
Sentiment and the balance of points
Rhea-AI Sentiment reads the wording of the document, how positive or negative its language is on a 1 to 5 scale. The balance of points shown with the takes weighs what the document actually discloses, so the two can disagree, for example when a trial that missed its main goal is described in upbeat language.
Rhea-AI Filing Summary
Seres Therapeutics, Inc. (MCRB) reported third-quarter 2026 results and advanced SER-155 plans to prevent immune checkpoint inhibitor-related enterocolitis (irEC). Grant revenue was $593,000, versus $351,000 a year earlier. Net loss was $16.286 million, compared with net income of $8.204 million in the prior-year quarter, which included a $27.222 million gain on sale of the VOWST Business.
Cash and cash equivalents were $17.528 million as of September 30, 2026. Including a $12.5 million payment received from Nestlé in October, Seres expects available resources to fund operations through the first quarter of 2027; that projection excludes potential future partnership or other capital proceeds.
In an investigator-sponsored trial, 12 of 15 participants with moderate-to-severe irEC (80%) achieved an immunosuppressive-free clinical response at Day 15, with no drug-related serious adverse events observed. The next study is expected to include dose optimization, with design submission to the FDA anticipated in the first quarter of 2027. SER-155 is also Phase 2 ready for allo-HCT, pending funding; the presentation reported a 77% relative risk reduction in bloodstream infections in Phase 1b.
How this balance works
Rhea-AI gives every point it takes from this document a weight. Minor counts 1, Moderate 3 and Major 9, so one Major point outweighs several Minor ones. The bar adds up the weights on each side, and when neither side holds more than 65% of the total the balance reads Mixed.
It reads the document as published, with the same rules for every company, and it does not look at what the market expected or at how the stock traded, so a point can be objectively good on a day the stock falls.
Rhea-AI Sentiment measures something else, the tone of the wording.
Hollow bars mark forward-looking points. How the balance works
Positive
- Minor pointGrant revenue: $593,000 in Q3 2026, versus $351,000 a year earlier.
- Minor pointSER-155: 80% immunosuppressive-free response at Day 15 in a 15-participant trial.
Negative
- Major pointQuarterly result: $16.286 million net loss versus $8.204 million net income.
- Major point. Forward-looking: it has not happened yet and may not happen.Cash runway: operations projected funded through Q1 2027.
Filing Explained
Common shares issued and outstanding were 10,049,501 on September 30, 2026, compared with 9,556,466 on December 31, 2025; the higher reported share count means an unchanged holding represented a smaller fraction of outstanding common shares.
8-K Event Classification
Key Figures
Key Terms
investigator-sponsored trial medical
immunosuppressive-free clinical response medical
allogeneic hematopoietic stem cell transplant medical
Breakthrough Therapy regulatory
IND-enabling studies medical
Earnings Snapshot
Seres expects available cash resources, including the $12.5 million payment received from Nestlé in October, to fund operations through the first quarter of 2027; the projection excludes proceeds from potential future partnerships or other sources of capital.
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
What was MCRB's net result in Q3 2026?
How many patients responded to SER-155 in the MCRB irEC trial?
When does MCRB expect to submit the SER-155 irEC study design to the FDA?
How long does MCRB expect its cash to fund operations?
AI-generated analysis. How Rhea-AI works. Not financial advice.
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM
CURRENT REPORT
Pursuant to Section 13 or 15(d)
of the Securities Exchange Act of 1934
Date of Report (Date of earliest event reported):
(Exact name of Registrant as Specified in Its Charter)
| (State or other jurisdiction of incorporation) |
(Commission File Number) |
(IRS Employer Identification No.) |
| (Address of principal executive offices) | (Zip Code) |
Registrant’s telephone number, including area code:
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 |
Name of each exchange | ||
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 November 4, 2026, Seres Therapeutics, Inc. (the “Company”) announced its financial results for the quarterly period ended September 30, 2026 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 November 4, 2026, the Company posted an updated corporate presentation (the “Corporate Presentation”) to its website. A copy of the Corporate Presentation is furnished 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
| Exhibit No. |
Description | |
| 99.1 | Seres Therapeutics, Inc. Press Release issued November 4, 2026 | |
| 99.2 | Seres Therapeutics, Inc. Corporate Presentation dated November 4, 2026 | |
| 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. | ||||||
| Date: November 4, 2026 | By: | /s/ Thomas J. DesRosier | ||||
| Name: | Thomas J. DesRosier | |||||
| Title: | Executive Vice President and Chief Legal Officer | |||||
Exhibit 99.1
SERES THERAPEUTICS REPORTS THIRD QUARTER 2026 FINANCIAL RESULTS AND ANNOUNCES PLANS FOR ADVANCING DEVELOPMENT OF SER-155 TO PREVENT IMMUNE CHECKPOINT INHIBITOR-RELATED ENTEROCOLITIS (irEC)
Prevention approach aims to keep patients on immune checkpoint inhibitor (ICI) therapy and avoid immunosuppressive irEC treatments, representing an additional broad therapeutic opportunity for SER-155
Seres expects to submit plans for the next irEC study design to the FDA in Q1 2027
Study builds on encouraging investigator-sponsored trial (IST) results, in which 12 of 15 participants (80%) with moderate-to-severe irEC achieved an immunosuppressive-free clinical response of diarrhea following treatment with SER-155
CAMBRIDGE, Mass., November 4, 2026 — Seres Therapeutics, Inc. (Nasdaq: MCRB), (Seres or the Company), a leading live biotherapeutics company, today reported third quarter 2026 financial results and announced it is progressing plans for a next study evaluating SER-155 for the prevention of immune checkpoint inhibitor-related enterocolitis (irEC) in patients initiating immune checkpoint inhibitor (ICI) cancer therapy, which is expected to include a dose optimization component. The Company anticipates submitting the study design to the FDA in the first quarter of 2027.
The planned study builds on previously announced positive topline results from an investigator-sponsored trial (IST) conducted at Memorial Sloan Kettering Cancer Center (MSK) in patients with moderate-to-severe irEC, in which 80% of participants achieved an immunosuppressive-free clinical response at Day 15, following treatment with SER-155. SER-155 was well tolerated, with no drug-related serious adverse events observed. irEC is a frequent and debilitating adverse reaction associated with widely used ICI cancer therapy that often requires patients to halt life-saving ICI treatment and begin systemic immunosuppressive corticosteroids. irEC is listed as an adverse reaction in the labels of all approved ICIs, including PD-1 inhibitors (Keytruda®, Opdivo®, Zynyz®), PD-L1 inhibitors (Imfinzi®, Bavencio®), CTLA-4 inhibitors (Yervoy®, Imjudo®), and LAG-3 inhibitor (Opdualag) - all of which were therapies received by patients in the IST.
“The irEC IST provided promising evidence that orally administered SER-155 improved epithelial barrier integrity and reduced gastrointestinal inflammation without systemic immunosuppression and was well-tolerated in patients with ICI-induced enterocolitis, “ said Richard Kender, Executive Chairman and Interim Chief Executive Officer of Seres. “Based on those results, and in consultation with key opinion leaders in the field, we determined that developing SER-155 to prevent irEC could address a significant unmet clinical need in patients being treated with ICIs for their cancer. We believe SER-155 may enable ICI patients, of whom there are currently estimated to be approximately 300,000 in the U.S. alone, to remain on their therapy by reducing the occurrence of irEC, which often requires the halting of life-saving cancer treatment. We also think this development approach offers a time and capital efficient path to clinical data and positions SER-155 to potentially address a broad ICI-treated population and
look forward to submitting our planned study design to the FDA in the first quarter of 2027. We are pleased to have two oncology-focused programs for SER-155, one with the goal of preventing irEC, and the other, in allogeneic hematopoietic stem cell transplant (allo-HCT), aimed at reducing the risk of bloodstream infections, a leading cause of mortality in these patients. We continue to seek capital through partnerships and other sources to advance our programs in irEC and in allo-HCT, which is Phase 2 ready, pending funding.”
Recent Highlights
SER-155 for the prevention of irEC
| • | Seres intends to advance SER-155 into a next study evaluating prophylactic oral administration in patients initiating ICI therapy, with a dose optimization component, dependent on funding. The study is being designed in consultation with leading oncologists and irEC experts. As part of the development program, Seres plans to engage with the FDA to discuss study design and potential endpoints, which could include incidence of irEC (all grades), ICI administration, and safety. In addition, Seres looks forward to receiving FDA feedback on plans to optimize prophylactic dosing for the study, which could include a healthy volunteer study component or a dosing lead-in element, the results of which are expected to inform the prophylactic dosing course, before initiating dosing in the broader ICI population. As in the completed IST, the Company anticipates enrolling patients across a wide range of ICI types. |
| • | The prevention approach is designed to reduce incidence of irEC, keep patients on ICI therapy and avoid immunosuppressive irEC treatments. irEC is among the most frequent and severe immune-related adverse reactions in patients receiving ICIs, and affects up to 50% of ICI recipients, with rates varying by ICI type and regimen. Current standard of care for moderate or worse irEC (Grade 2 or above) requires halting life-saving ICI therapy and initiating a systemic immunosuppressive corticosteroid, a biologic, or both, which carry their own toxicities and may compromise the anti-cancer effect of ICI therapy. |
| • | The planned next study builds on encouraging topline results from the open-label IST (NCT06801067) conducted at MSK evaluating SER-155 as a potential treatment in irEC, which Seres reported in July. The study enrolled 15 participants with moderate-to-severe (Grade 2-3) irEC (which represents approximately 25% of all ICI recipients) who were naïve to immunosuppressive therapy; 12 of 15 (80%) of participants treated with SER-155 achieved an immunosuppressive-free clinical response at Day 15, the primary efficacy endpoint, defined as at least a one-grade improvement in diarrhea symptoms without immunosuppressive therapy. Five of 15 participants (33%) achieved immunosuppressive-free complete clinical remission at Day 15. SER-155 was generally well tolerated through Day 43, with no serious adverse events assessed as related to SER-155. |
| • | In the IST, translational biomarkers of gastrointestinal inflammation and mucosal epithelial barrier integrity both improved following SER-155 treatment, with statistically significant reductions by Day 43. |
| • | ICIs represent one of the largest and fastest-growing segments of the oncology market, with the worldwide market valued at well over $50 billion in 2025. In the U.S. alone, it is estimated that 300,000 patients are currently on ICIs, representing a large potential target patient population for SER-155 as a preventative treatment for irEC, and a potential multi-billion-dollar commercial opportunity, as the Company believes that both patients and clinicians will be motivated to adopt a prophylactic approach that could permit patients to remain on their ICI therapy. |
| • | Seres expects to submit the proposed next study design to the FDA in the first quarter of 2027 and engage with the agency thereafter. |
| • | Seres and MSK will present a poster entitled “High Immunosuppressive-Free Response Rate of irEC with SER-155, an Investigational Oral Live Biotherapeutic, as First-Line Therapy, in a Phase 1b Study” at the Society for Immunotherapy of Cancer (SITC) 2026 Annual Meeting in Phoenix, AZ on November 7, 2026. This poster will highlight the promising results of the IST. |
Broader pipeline and portfolio
| • | SER-155 remains Phase 2 ready for the prevention of bloodstream infections in adults undergoing allo-HCT for the treatment of blood cancer, pending funding. SER-155 has received Breakthrough Therapy and Fast Track designations for this indication. Efforts continue to secure funding to advance clinical development for this program. |
| • | On November 3, Seres announced that results from its Phase 1b clinical study of SER-155 in adults undergoing allo-HCT were published in Nature Medicine, marking an important milestone for the program and providing recognition of the innovative science being advanced by the Company. The publication reported that SER-155 was generally well tolerated and was associated with a 77% relative risk reduction in BSIs compared with placebo. |
| • | Seres continues to progress development of SER-428, an investigational oral liquid formulation based on a subset of SER-155 strains supported by a grant from CARB-X (Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator), for dosing in patients who cannot take oral capsules, including critically ill patients who receive nutrition and medications via feeding tube. Seres is designing a Phase 1b open-label trial, in collaboration with Daniel E. Freedberg, M.D., M.S., of Columbia University, and in consultation with CARB-X, to evaluate SER-428 in patients with sepsis who are receiving antibiotics in the Medical Intensive Care Unit (MICU) and are at high risk of additional infection. Further clinical development of SER-428 will be progressed pending funding from grants or other sources. |
| • | The Company continues to advance IND-enabling activities for SER-603, in development for inflammatory bowel disease (IBD), and is engaging potential collaborators to support the clinical advancement of this program as a mono and/or combination therapy. |
Corporate Updates
| • | In October, Seres received the second of the two $12.5 million payments related to the buy-out of potential future VOWST net sales-based milestones from Nestlé Health Science (Nestlé). |
| • | On July 31, Seres entered into an agreement to terminate the lease for its facility at 200 Sidney Street in Cambridge, MA. The early termination materially eliminates the Company’s obligations under the lease as of December 31, 2026, and results in reduced ongoing facility-related cash costs beginning in 2027. |
Third Quarter 2026 Financial Results
| • | Net loss was $16.3 million for the third quarter of 2026, compared to net income of $8.2 million for the same period in 2025. The difference is primarily due to a $25 million installment payment received in the third quarter of 2025 related to the sale of the VOWST business to Nestlé, recognized as a Gain on Sale. |
| • | Research and development expenses were $5.6 million for the third quarter of 2026, compared with $12.6 million for the same period in 2025, reflecting lower facilities costs, transition services agreement (TSA) costs, personnel-related expenses and SER-155 costs driven by lower activities in these areas and cost reduction efforts. |
| • | General and administrative expenses were $5.4 million for the third quarter of 2026, compared with $9.5 million for the same period in 2025, due to lower personnel-related expenses, facilities costs, and IT costs, including those related to IT services provided under the TSA. |
| • | In the third quarter of 2026, the Company recorded a $5.7 million non-cash impairment of assets charge related to the early termination of its lease at 200 Sidney Street. |
Cash and Cash Runway
As of September 30, 2026, Seres had $17.5 million in cash and cash equivalents. Based on Seres’ currently available cash resources, including the $12.5 million payment received from Nestlé in October, and considering future operating plans, the Company expects to fund operations through the first quarter of 2027. This projection excludes proceeds from any potential future partnerships or other sources of capital.
About Seres Therapeutics
Seres Therapeutics, Inc. (Nasdaq: MCRB) is a clinical-stage biotechnology company developing novel live biotherapeutics products in oncology that address causes of mortality and discontinuation of life-saving cancer treatment, and in inflammatory and immune (I&I) diseases, by modulating host function to protect and improve mucosal epithelial barrier integrity, induce immune homeostasis and tolerance, and prevent the colonization and overgrowth of pathogens in the gastrointestinal (GI) tract. The Company previously led the development and FDA approval of VOWST™, the first orally administered microbiome therapeutic, which was subsequently divested to Nestlé Health Science. SER-155, an investigational cultivated multi-strain biotherapeutic, which has received Breakthrough Therapy and Fast Track designations, is being advanced for the prevention of bloodstream infections in patients undergoing allogeneic hematopoietic stem cell transplant (allo-HCT), and is Phase 2 ready, pending receipt of funding. SER-155 is also being developed to prevent immune checkpoint inhibitor-related enterocolitis (irEC), with the aim of enabling patients to continue their ICI cancer therapy and avoid the need for immunosuppressive steroid treatment. Following promising results from an investigator-sponsored trial, Seres plans to submit the design of a study for the prevention of irEC in patients initiating ICI therapy to the FDA. The Company is advancing IND-enabling studies for SER-603, which is in development for inflammatory bowel disease. Mechanistically, Seres’ biotherapeutics target the mucosal epithelial barrier-immune interface and are optimized to modulate host function to increase mucosal epithelium integrity, induce immune homeostasis, and prevent the colonization and overgrowth of harmful bacteria in the GI tract. For more information, please 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, without limitation, statements about: SER-155 and its intended uses and benefits in irEC; our clinical development plans for SER-155, SER-603 and SER-428, including the design and timing of the next planned study of SER-155 for the prevention of irEC; potential accessibility for patients; planned submissions to and/or engagement with regulatory authorities, including the anticipated timing of FDA feedback; the timing and results of clinical studies and data readouts; the anticipated content and timing of upcoming presentations and conferences; current or future product candidates and their potential impacts and outcomes; the size of potential patient populations and markets and the potential commercial opportunity for SER-155; engagement with potential partners and financing sources; our ability to access capital to advance our programs; IND-enabling activities; our cash runway; the anticipated effects of our lease termination, including expected reductions in facility-related costs; 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 cost reduction actions may not achieve their intended benefits, including an extended cash runway; (5) our limited operating history; (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; (13) impact of our recent management transitions and appointments and our ability to retain key personnel; and (14) disruptions at the FDA or other government agencies. These and other important factors discussed under the caption “Risk Factors” in our Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2026, to be filed with the Securities and Exchange Commission (SEC), 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, except as required by law, 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)
| September 30, 2026 |
December 31, 2025 |
|||||||
| Assets |
||||||||
| Current assets: |
||||||||
| Cash and cash equivalents |
$ | 17,528 | $ | 45,766 | ||||
| Accounts receivable due from SPN - related party |
12,500 | 360 | ||||||
| Accounts receivable |
183 | 157 | ||||||
| Prepaid expenses and other current assets |
4,212 | 3,093 | ||||||
|
|
|
|
|
|||||
| Total current assets |
34,423 | 49,376 | ||||||
| Property and equipment, net |
2,999 | 7,635 | ||||||
| Operating lease assets |
27,662 | 72,483 | ||||||
| Restricted cash |
773 | 8,668 | ||||||
| Other non-current assets |
31 | 31 | ||||||
|
|
|
|
|
|||||
| Total assets |
$ | 65,888 | $ | 138,193 | ||||
|
|
|
|
|
|||||
| Liabilities and Stockholders’ Equity |
||||||||
| Current liabilities: |
||||||||
| Accounts payable |
$ | 1,461 | $ | 1,682 | ||||
| Accrued expenses and other current liabilities |
3,504 | 3,972 | ||||||
| Accrued liabilities due to SPN - related party |
3,278 | 3,278 | ||||||
| Operating lease liabilities |
12,650 | 10,390 | ||||||
|
|
|
|
|
|||||
| Total current liabilities |
20,893 | 19,322 | ||||||
| Operating lease liabilities, net of current portion |
23,122 | 72,576 | ||||||
| Other long-term liabilities |
514 | 2,077 | ||||||
|
|
|
|
|
|||||
| Total liabilities |
44,529 | 93,975 | ||||||
|
|
|
|
|
|||||
| Commitments and contingencies (Note 9) |
||||||||
| Stockholders’ equity: |
||||||||
| Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2026 and December 31, 2025; no shares issued and outstanding at September 30, 2026 and December 31, 2025 |
— | — | ||||||
| Common stock, $0.001 par value; 360,000,000 shares authorized at September 30, 2026 and December 31, 2025; 10,049,501 and 9,556,466 shares issued and outstanding at September 30, 2026 and December 31, 2025, respectively |
10 | 10 | ||||||
| Additional paid-in capital |
1,025,370 | 1,016,611 | ||||||
| Accumulated deficit |
(1,004,021 | ) | (972,403 | ) | ||||
|
|
|
|
|
|||||
| Total stockholders’ equity |
21,359 | 44,218 | ||||||
|
|
|
|
|
|||||
| Total liabilities and stockholders’ equity |
$ | 65,888 | $ | 138,193 | ||||
|
|
|
|
|
|||||
SERES THERAPEUTICS, INC.
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE (LOSS) INCOME
(unaudited, in thousands, except share and per share data)
| Three Months Ended September 30, |
Nine Months Ended September 30, |
|||||||||||||||
| 2026 | 2025 | 2026 | 2025 | |||||||||||||
| Revenue: |
||||||||||||||||
| Grant revenue |
593 | 351 | 1,687 | 351 | ||||||||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Total revenue |
593 | 351 | 1,687 | 351 | ||||||||||||
| Operating expenses: |
||||||||||||||||
| Research and development expenses |
5,592 | 12,616 | 27,928 | 37,376 | ||||||||||||
| General and administrative expenses |
5,448 | 9,476 | 20,579 | 31,617 | ||||||||||||
| Impairment of long-lived assets |
5,705 | — | 11,512 | — | ||||||||||||
| Manufacturing services |
— | 736 | — | 5,952 | ||||||||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Total operating expenses |
16,745 | 22,828 | 60,019 | 74,945 | ||||||||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Loss from operations |
(16,152 | ) | (22,477 | ) | (58,332 | ) | (74,594 | ) | ||||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Other income (expense): |
||||||||||||||||
| Gain on sale of VOWST Business |
— | 27,222 | 25,000 | 79,588 | ||||||||||||
| Interest income |
146 | 618 | 652 | 1,782 | ||||||||||||
| Other income (expense) (1) |
(280 | ) | 2,841 | 1,062 | 14,255 | |||||||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Total other income (expense), net |
(134 | ) | 30,681 | 26,714 | 95,625 | |||||||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Net (loss) income and comprehensive (loss) income |
$ | (16,286 | ) | $ | 8,204 | $ | (31,618 | ) | $ | 21,031 | ||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Net (loss) income per share attributable to common stockholders - basic |
$ | (1.63 | ) | $ | 0.94 | $ | (3.24 | ) | $ | 2.41 | ||||||
| Net (loss) income per share attributable to common stockholders - diluted |
$ | (1.63 | ) | $ | 0.94 | $ | (3.24 | ) | $ | 2.40 | ||||||
|
|
|
|
|
|
|
|
|
|||||||||
| Weighted average common shares outstanding - basic |
9,982,031 | 8,758,692 | 9,764,763 | 8,735,418 | ||||||||||||
| Weighted average common shares outstanding - diluted |
9,982,031 | 8,771,519 | 9,764,763 | 8,744,797 | ||||||||||||
|
|
|
|
|
|
|
|
|
|||||||||
| [1] | Includes $0, $0, $2,028, and $11,827 for the three and nine months ended September 30, 2026 and 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
Company Overview Harnessing the therapeutic potential of microbes to advance the treatment of cancer and inflammatory & immune diseases 2026Q3 Exhibit 99.2
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 design, timing and results of our current or planned preclinical and clinical trials, 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 partnership and or funding sources; the advancement of IND-enabling activities; our drug candidates and their potential impacts and outcomes, including the potential market and commercial opportunity for SER-155, if approved; operating plans and our future cash runway; 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 these 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 cost reduction actions may not achieve their intended benefits, including an extended cash runway; (5) our limited operating history; (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) the impact of our recent management transitions and appointments and our ability to retain key personnel; and (14) disruptions at the FDA or other government agencies. These and other important factors discussed under the caption "Risk Factors" in our Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2026, to be filed with the Securities and Exchange Commission (SEC) on November 4, 2026, 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 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.
Seres has pioneered a new drug modality and accessed the vast functional and therapeutic potential of microbes to treat and prevent disease Achieved two Breakthrough Therapy Designations (VOWST & SER-155) Clinically demonstrated biotherapeutics can target the mucosal epithelial barrier-immune interface and achieve placebo-like safety profile across multiple patient populations AI-enabled MbTx® Platform that interrogates microbe-host functional interactions and their links to disease and patient heterogeneity with demonstrated clinical translation of targeted mechanisms of action 2023 FDA approval and launch* Track-record of realizing ambitious, impactful therapeutic goals: First company to go from novel concept through clinical development to FDA approval/commercialization of oral biotherapeutic (VOWST™) *VOWST US & Global rights sold to NHSc in 2024 Two programs in oncology that address causes of mortality and discontinuation of life-saving treatment in cancer patients Focused on addressing unmet medical needs in oncology and inflammatory & immune disease with broad potential based on uniquely targeting the mucosal epithelial barrier-immune interface Novel drug modality with potential to target upstream drivers of inflammatory responses and challenges of antimicrobial resistance infections
Harnessing the therapeutic potential of microbes with live biotherapeutics Formulated for oral administration; manufactured from master cell banks Consortia of bacteria that are optimized to produce therapeutically active metabolites that target multiple disease-relevant pathways Clinical translation achieved on targeting mucosal epithelial barrier-immune interface drivers of disease Well-tolerated safety profile across multiple patient populations reducing clinical development risk Microbe-human functional interactions co-evolved for millions of years and are integral to the body’s immune & metabolic function
Addressing critical, unmet medical needs in oncology and inflammatory & immune diseases that are linked to disrupted mucosal epithelial barrier and immunity Hematopoietic allogeneic stem cell transplant (allo-HCT) Patients are severely immune compromised with high-risk of bloodstream infections (BSIs) post stem cell transplant BSIs, many that are antimicrobial resistant infections, are the leading cause of death in first 100 days post stem cell transplant in adults; ~7.5% mortality rate from BSI. Recent increased use of post-transplant cyclophosphamide for GvHD is increasing BSI risk by ~2.4-fold Immune checkpoint inhibitor related enterocolitis (irEC) Activation of immune cells by immune checkpoint inhibitor therapy (ICI) to attack cancer tumors can damage healthy tissues causing severe diarrhea and colitis (irEC) and hospitalization Up to 50% of ICI patients can experience irEC depending on ICI type/regimen; Moderate-to-severe (Grade 2-3) irEC occurs in ~25% of ICI patients and Grade 2 or higher requires treatment and disrupts life-saving cancer treatment Current immunosuppressive treatment options are inadequate with negative side effects Inflammatory Bowel Disease (IBD) Current treatments have an efficacy ceiling due to non-response or poor durability of response Safety profile of immune suppressive treatments limit the potential for combining advanced therapies to improve efficacy Available therapies do not target upstream drivers of disease Patient heterogeneity is a core challenge and key reason many drugs have limited efficacy and durability SER-155, Breakthrough Therapy Phase 2 Ready SER-155 FDA engagement planned for next study SER-603 IND-enabling Studies underway
SER-155 Allo-HCT: Ph1b demonstrated 77% relative risk reduction in bloodstream infections (BSI) and well-tolerated FDA Breakthrough Therapy Opportunity Prevent bloodstream & antimicrobial resistant (AMR) infections linked to mortality in allo-HCT recipients and other blood cancer patients Infectious disease and hematology-oncology physicians rank BSIs in allo-HCT as a 6 on 7-point scale of risk concern Allo-HCT is a costly procedure (~$400K US year per patient); incremental costs of infections are significant (incremental ~$242K/patient). ~40K allo-HCT transplants worldwide annually with indication expansion potential in additional cancer patients at high risk of infection (~560K) Opportunity - Phase 2 Ready - Agreement with FDA on study design; interim analysis may enable expedited development path Primary endpoint: relative risk reduction in BSI (placebo-controlled, mITT n=34) % participants with a BSI Observed reduction in febrile neutropenia Observed significant reductions (p ≤ 0.05) in healthcare utilization, days of antibiotics use, and hospitalization Efficacy, safety & drug pharmacology reported in Ponce et al. 2026. Nature Medicine Well-tolerated; No Drug-related Serious Adverse Events (SAEs) identified Clinical Efficacy & Safety 77% Relative risk reduction (p<0.05)
SER-155 irEC: Investigator sponsored Phase 1b study demonstrated 80% immunosuppressive-free clinical response and well-tolerated Primary endpoint: Immunosuppressive-free clinical response at Day 15 (open label n=15) 80% 80% of all participants achieved Response (diarrhea decrease by one or more Grades) 33% of all participants achieved Remission (Grade 0; no diarrhea) Grade 0: 5 of 12 participants Grade 1: 7 of 12 participants Well-tolerated; No Drug-related Serious Adverse Events (SAEs) identified Clinical Efficacy & Safety Enable patients receiving immune checkpoint inhibitors to remain on life-saving cancer treatment Immune checkpoint inhibitors revolutionized cancer treatment and represent an ~$50B global market; an estimated 300,000 and ~3M patients are projected to be treated in US and worldwide in 2026 Immune checkpoint inhibitors cause irEC in up to 50% of patients depending on ICI type/regimen; moderate-to-severe (Grade 2-3) irEC occurs in ~25% of ICI patients and Grade 2 or higher disrupts life-saving cancer treatment and requires treatment with immune suppressive drugs that have additional side-effects. Grades 4-5 are life-threatening Opportunity - FDA engagement planned for next study – Positive engagement with KOLs on study design
SER-603 IBD: Improves response to IBD drugs in preclinical models and Seres unique translational biomarkers can predict response to advanced biologics SER-603 targets unique upstream mechanisms of action to treat inflammation with potential as mono- or combo-therapy to address efficacy ceiling Expand therapeutic and commercial potential for existing IBD therapies by increasing response rates and expanding durability of response Opportunity - IND enabling studies underway - Start of biologic ± SER-603 Achieve greater efficacy using combination therapy of SER-603 + biologic (anti-TNF-α) SER-603 can also significantly reduce inflammation as monotherapy (data not shown) SER-603 + biologic intervention SER-603 alone (negative control) Biologic (Anti-TNFa) only Biomarker(+) Inflammatory microbiome Model: Microbe-driven inflammation in IL-10-/- mice Convert partial and non-responding inflammatory bowel disease patients to clinical responders Address current biologics efficacy ceiling by targeting upstream drivers of disease not currently accessed and without immunosuppression Seres identified & confirmed novel, microbial-linked biomarkers that can predict response to current IBD therapies to address challenge of patient heterogeneity Potential in mild-to-moderate and moderate-to-severe patients; >700K (UC & Crohn’s) and >900K (UC) in the US respectively Days post dosing Inflammation (ng/g fecal lipocalin2) Preclinical
Seres has clinically translated targeting the mucosal epithelial barrier-immune interface Gastrointestinal Mucosal Epithelial Barrier-Immune Interface GI lumen Epithelium Lamina propria Mucosa Disruption leads to translocation of pro-inflammatory molecules and microbes that drive aberrant host immune responses causing inflammatory and immune disease, and infection Seres biotherapeutics target multiple upstream drivers of mucosal epithelial barrier disruption, inflammation and infection without being immunosuppressive Current therapies only target downstream via immune suppression Inhibit Inflammatory Microbes & Pathogens Intestinal Mucosal Epithelial Barrier Integrity Immune Function and Regulation
Seres has full stack platform capabilities & experience in novel biotherapeutic modality that has delivered two Breakthrough Therapies and a drug licensure Seres has built field-leading biological, clinical microbiome, and manufacturing capabilities with proven ability to design, develop, and receive FDA approval in a novel modality MbTx® Platform AI and ML enabled engine that interrogates microbe-host functional interactions and their links to disease and patient heterogeneity with demonstrated clinical translation Field-leading Microbiome biomarker & drug target identification --- strains, metabolites/peptides, genes Demonstrated Clinical Translation & Identification of Patient Subpopulations --- novel drug modality PK/PD/MoAs; biomarkers for patient heterogeneity; receipt of breakthrough designation Efficient Lead Candidate Design, Screening, Optimization --- expansive strain library with screening & models adapted for novel drug modality Field-leading Manufacturing & Clinical Development Successfully advanced multiple biotherapeutics into early- and late-stage clinical trials with an FDA licensure achieved Proven Regulatory Expertise --- Pioneered regulatory path for novel drug modality with FDA approval Exceptional Clinical Trial Execution --- Proprietary know-how on trial design, enrollment in challenging populations, drug pharmacology & sample collection Demonstrated Novel Therapeutic GMP Manufacturing & Quality --- spans broad biological breadth with demonstrated commercial success and clean regulatory inspection history
Focused strategy to advance novel biotherapeutics and deliver shareholder value Capital Strategy & Financial position Seres efforts ongoing to seek partnerships and funding to support continued development toward meaningful clinical milestones across pipeline assets Recent balance sheet strengthening actions: Nestlé Health Science buy-out of potential future VOWST™ net sales-based milestones ($25 million received) and restructuring of two leases, including early terminations, to materially reduce leased space and ongoing annual facilities cash costs Cash runway projected through Q1 2027 Pipeline of novel live biotherapeutics in areas each with multibillion commercial potential Two programs in oncology that address causes of mortality or discontinuation of life-saving treatment in cancer patients Bloodstream and antimicrobial resistant infections in stem cell transplant (allo-HCT) and blood cancers Partner Breakthrough Therapy, Phase 2 ready SER-155 program and achieve study interim analysis (~12 months from FPI) to enable expedited path to licensure discussion with regulators Immune checkpoint inhibitor-related enterocolitis (irEC) Develop prophylaxis clinical protocol and engage FDA in 2027Q1 Position promising preclinical biotherapeutic programs that target mucosal epithelial barrier-immune interface associated inflammatory and immune diseases and antimicrobial resistant infections for future clinical development
Pipeline: Seres biotherapeutics target mucosal epithelial barrier-immune associated inflammatory diseases and infection leveraging years of clinical progress and data Preclinical Ph1 Ph2 Ph3 Enabling Collaborators IND-enabling studies underway; Potential to target upstream disease pathways that current therapies cannot access and to predict response to advanced biologics Breakthrough Therapy Designation; Phase 2 ready; Ph1b demonstrated well-tolerated and 77% relative risk reduction in blood stream infections with clinical translation of mucosal barrier integrity MoA SER-155 for preventing pathogen translocation and resulting bloodstream and AMR infections in allo-HCT SER-603 for inflammatory bowel disease (IBD) Topline Readout for Investigator sponsored Phase 1b in 2026Q2; Ph1b demonstrated 80% immunosuppressive-free clinical response; potential to address one of most significant immune checkpoint inhibitor AEs; Prophylactic trial design in progress SER-155 for immune checkpoint related enterocolitis (irEC) IND-enabling studies underway; Novel liquid formulation suitable for targeting bloodstream and antimicrobial resistant infections in patients unable to swallow capsules (e.g., intubated patients in ICU) SER-428 for reducing AMR infections in ICU AMR = Antimicrobial resistant infections ICU = Intensive care unit AE = Adverse event Lead screening & drug candidate nomination; Potential to address multiple complications of decompensation in cirrhosis patients SER-147 for reducing spontaneous bacterial peritonitis
SER-155 Allogeneic hematopoietic stem cell transplant (allo-HCT) --- Prevention epithelial barrier damage and resulting bloodstream infections (BSI) that can lead to mortality Breakthrough Therapy Designation & Phase 2 Ready
Infection is the leading cause of death in first 100 days post-HCT, and recent increased use of post-transplant cyclophosphamide (PTCy) for GvHD is increasing bloodstream (BSI) risk by ~2.5-fold Translocation of pathogens are a significant problem in allogeneic hematopoietic cell transplant patients (allo-HCT) and leading cause of mortality HCT conditioning chemotherapy and frequent antibiotic use leads to gastrointestinal (GI) pathogen domination and compromised mucosal epithelial barrier that can lead to translocation of bacteria to bloodstream Allo-HCT patients are severely immunocompromised with high-risk of bloodstream infections (BSIs) post-HCT, especially HCT Day 0-30 Infection is the leading cause of death in first 100 days post-HCT in adults, ~7.5% mortality rate from BSI; Efficacy of prophylactic antibacterials to prevent BSI is increasingly limited by antimicrobial resistance Infectious disease and hematology-oncology physicians are highly concerned about BSIs in allo-HCT patients; rank BSIs as 6 on 7-point scale* of risk concern and indicate effective prophylaxis is a major unmet need *Seres primary market research 2024 Trinity Life Sciences survey of hematologists and infectious disease specialists
A significant unmet need exists to prevent bloodstream (BSI) and antimicrobial resistant (AMR) infections in immunocompromised patients Address conditioning chemotherapy and prophylactic antibiotic use damage to gastrointestinal microbiome and mucosal epithelial barrier that lead to infections Reduce prophylactic antibiotics use that are increasing the risk of antimicrobial resistant infections Prevent infections while highly immunocompromised transplant patients recover immune system function SER-155, an investigational live biotherapeutic, has potential to prevent BSI and associated mortality, and to reduce antibiotic use that leads to antimicrobial resistance (AMR) -- Potential to address both the causes and antibiotic treatment limitations of bloodstream infections
SER-155 has the potential to become a critical component of care of immunocompromised patients — Prevent infections that lead to medical complications and mortality Top-Line Results Summary: SER-155 prevented bloodstream infections and protected and repaired the mucosal epithelail barrier integrity Efficacy 77% relative risk reduction in bloodstream infections (BSI) compared to placebo (p<0.05; primary endpoint) Safety Well-tolerated with No Drug related Serious Adverse Events (SAEs) identified Drug Pharmacology Observed clinical translation on reduction in pathogen burden in gastrointestinal tract and protection and repair of mucosal epithelial barrier Phase 1b Randomized placebo-controlled 1:1 Cohort 2 (n=34 mITT); open-label Cohort 1 (n=11 mITT) established safety and PK/PD
Bloodstream infections (BSIs) are a leading cause of death post-transplant and are increasing in incidence with uptake of post-transplant cyclophosphamide (PTCy) 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 Majority of BSIs in first 30 days post-HSCT are seeded from the gastrointestinal tract 60-90% febrile neutropenia incidence Incidence 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 Sources: Gill et al, Microorganisms 2023; Sava et al, Bone Marrow Transplantation 2022; Carreira et al, Transplant Cell Ther 2022; Tamburini et al, Nature Med, 2018; Göldel, et al, Blood, 2024; Rearigh et al, Ann Hematol, 2020; Song et al, Infect Drug Resist 2023; Bolaños-Meade J et al, NEJM 2023; Salas et al, Transplant Cell Ther 2024; Nesher et al, Principles and Practice of Transplant Infectious Diseases, 2019 CIBMTR 2023 US summary slides; Perales et al Biol Blood Marrow Transplant 2017; Taplitz et al, J Clin Oncol 2018; Bolon et al, Current use and outcome of hematopoietic stem cell transplantation: CIBMTR summary slides, 2022. http://www.cibmtr.org; Poutsiaka, et al D., Bone Marrow Transplant, 2007
SER-155 Phase 1b in allo-HCT: Reduction in bloodstream infections, healthcare and antibiotic utilization, with placebo-like safety Significant reduction (p < 0.05) in bloodstream infection (BSI) incidence (HCT Day 0-30) Significant reduction (p ≤ 0.05) in healthcare utilization: days of antibiotics and hospitalization % participants with a BSI 77% Relative risk reduction *All participants received prophylactic antibiotics, intended to prevent BSI, as standard of care. Prophylactic antibiotics were highly associated with BSI bacteria exhibiting AMR. Resistance to multiple antibacterial classes was observed only in BSI bacteria with placebo treatment. Two placebo-treated participants with BSIs had fatal outcomes from the BSI. Mean Days of Systemic Treatment Antibiotic Use Mean Days of Hospitalization Numerical reduction (p > 0.05) in febrile neutropenia (FN) incidence Mean difference: -11.9; p=0.05 SER-155 (N=20) Placebo (N=14) Wilcoxon-Rank Sum, post hoc: p=0.05 % of participants with FN 14% absolute risk reduction 17% relative risk reduction FN and BSI are major drivers of systemic treatment antibiotic use, and thus potential drivers of antimicrobial resistance (AMR) Efficacy, safety & drug pharmacology reported in Ponce et al. 2026. Nature Medicine
SER-155 Phase 1b in allo-HCT: Clinical translation on all drug mechanisms of action further support observed efficacy results Rapid protection of gastrointestinal mucosal epithelial barrier integrity Substantial reduction in pathogen domination in the GI microbiome Improved immune homeostasis reflected in plasma cytokine profile SER-155 prevents the loss of GI epithelial barrier integrity due to HCT conditioning chemotherapy; Significantly lower (p ≤ 0.05) fecal albumin in SER-155 treated versus placebo post treatment SER-155 Placebo Healthy GI pathogen domination is associated with bloodstream infections and mortality in allo-HCT. SER-155 reduced multiple pro-inflammatory cytokines associated with the HCT procedures. Efficacy, safety & drug pharmacology reported in Ponce et al. 2026. Nature Medicine
SER-155 Safety: Generally well-tolerated with no treatment-related severe adverse events (SAEs) All but one subject in the placebo arm experienced at least 1 TEAE Most common for SER-155 treated subjects (≥50% and with a delta ≥5% more 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) 4/40 (10%) subjects experienced a TEAE leading to study discontinuation (active = 2; placebo = 2) 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 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 Treatment-Emergent Adverse Events (TEAEs) Serious Adverse Events (SAEs) Adverse Events of Special Interest (AESIs) Results above for Cohort 2 Safety Population
SER-155 BSI Path Forward: SER-155 is Phase 2 ready in allo-HCT and design provides opportunity for adjacent indication expansion Expansion: Auto-HCT, CAR-T & Cancer neutropenia Phase 2 Allo-HCT Allo-HCT bloodstream and antimicrobial resistant infections has strong biological adjacencies to auto-HCT, CAR-T, and blood cancers (e.g., AML & cancer neutropenia) Allo-HCT Phase 2 interim analysis data could trigger advancement in expansion indications Auto-HCT has similar treatment and conditioning regimens to allo-HCT; potential for for one pivotal registrational study in auto- triggered by allo-HCT interim analysis and initial BLA approval for both allo- and auto-HCT together may be possible Febrile neutropenia and BSI data at allo-HCT Phase 2 interim analysis could accelerate clinical evaluation in CAR-T & Cancer neutropenia/AML Received Fast Track and Breakthrough Designation FDA in agreement with Phase 2 study design (submitted to FDA January 2026) FDA open to expedited path to engage and start Phase 3 if the interim analysis shows overwhelming efficacy Finalized Protocol Clinical Site infrastructure in place and key manufacturing steps advanced
US annual diagnoses or transplants Unmet needs addressed by SER-155 Allo-HCT ~9,300 Prevent mortality and cost of post-transplant infections Autologous HCT ~13,500 Prevent mortality and costs of post-transplant infections Cancer Neutropenia / Broader leukemia & lymphoma population* ~87,000 initial focus Reduce morbidity, mortality, and costs of infections & FN 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) at risk Sources: WBMT Global Transplant Activity Data, CIBMTR 2024 and 2025 annual reports, US NCI SEER Cancer Stat Facts 2026, National Pharmaceutical Council-2025 CAR-T Cell Therapy Transformation Report; Thandra et al 2021 report of WHO data, Niederwieser et al Haematologica 2022; Greco et al 2026 the 2024 EMBT activity report, Bone Marrow Transplant; WHO/IARC Global Cancer Observatory-GLOBOCAN 2022; American Cancer Society, Cancers Facts and Figures 2026 WW annual diagnoses or transplants ~40,000 ~60,000 ~500,000 SER-155 in allo-HCT commercial opportunity is meaningful and has indication expansion potential (~15x addressable population) creating multi-billion dollar opportunity , CAR-T ~10,000 ~20,000 Reduce life-threatening infections, CRS, ICANS & Enhance CAR-T efficacy
Infections in allo-HCT are costly; Merck viral prophylaxis drug provides precedent on commercial opportunity in medically vulnerable patients Sources: CMS.gov; Broder et al. 2017 Am Drug Health Benefits; Perales et al, 2017 Biol Blood Marrow Transplant; Merck SEC filings Cost of infections in 2015 dollars estimated at $177K by Perales, et.al. and inflated to 2025 costs (usinflationcalculator.com) Prevymis, a Merck product approved by FDA in 2017 and EMA in 2018, is experiencing broad use for CMV prophylaxis (viral infection) in allo-HCT recipients $978M 2025 WW sales (~25% growth over '24) Reduces CMV infection in allo-HCT recipients Lowers mortality rate Infections in allo-HCT result in significant incremental costs with longer hospital stays, more readmissions, and increased ICU utilization US Allo-HCT procedure: ~$400K year 1 per patient cost Transplant-related complications (e.g., infections) raise cost by ~$242K Prevymis cost: ~$30K; returned ICER $60K/QALY EU Allo-HCT procedure: ~$95K for transplant and ~$260K to $325K for year preceding plus 2 years following procedure Prevymis cost: $30K-$33K for 92 days (publicly available data from Germany, France, Italy, Spain) ICER in line with cost-effective thresholds in high income EU countries SER-155 targets prevention of bloodstream infections from bacterial pathogens that can lead to mortality
Value capture: highly concentrated prescriber universe enables lean commercial model Many key centers were Ph1b trial sites; plan to add more for future trials 185 US centers performed an allo-HCT in 2016-2020 ~80% of US transplants in 70 centers Similar concentration in most major European countries Concentrated prescriber universe Strong familiarity with SER-155 clinical program
SER-428 ICU BSI: Formulation to enable liquid oral dosing to expand prevention of infections in intubated and other patients unable to swallow capsules Liquid oral dosing of SER-428 decolonizes key pathogens that colonize the GI tract and are associated with infections and poor outcomes Expand prevention of bloodstream and antimicrobial resistant infections to patients at high infection risk & unable to swallow capsules Opportunity - IND submission pending – Drug manufacture & testing completed SER-428 is designed to be functionally similar to SER-155 SER-428 is the first liquid formulation developed for oral and enteral feeding tube delivery of live biotherapeutics Program supported in part by CARB-X Up to 1M sepsis patients in US admitted to hospitals with over half requiring ICU admission; most patients admitted to ICU with a known or suspected infection and receive broad-spectrum antibiotics Infections in the ICU are consequential; infection is leading cause of death for patients admitted to the ICU with sepsis; 40% all cause mortality for patients admitted to ICU who acquire BSI (including those treated for sepsis) Each BSI event can lead to 15 to17 excess hospital days and $42,000 to $55,000 in excess hospital costs per hospital-onset (Yu et al. 2023. Inf. Cont. & Hosp. Epi.) Preclinical Enterococcus faecium decolonization Klebsiella pneumoniae decolonization
SER-155 Immune Checkpoint Inhibitor-Related Enterocolitis (irEC) --- An Alternative To Immunosuppression That May Preserve Checkpoint Inhibitor Therapy Recent Topline Investigator Sponsored Study Results
irEC is a serious, frequent complication of rapidly growing immune checkpoint inhibitor therapy that requires immunosuppressive treatment and often disrupts life-extending cancer treatment What is Immune Checkpoint Inhibitor-Related Enterocolitis (irEC)? Immune Checkpoint inhibitors (ICIs) activate and amplify the immune system to attack cancer cells and save lives. The immune activation / amplification that attacks cancer tumors can attack healthy tissues, including in the gastrointestinal tract, causing irEC. irEC can cause severe diarrhea, abdominal pain, bloody stool, inflammation, colitis and hospitalization. Up to 50% of ICI patients can experience irEC depending on type/regimen; moderate-to-Severe irEC occurs in ~25% of patients receiving ICI (Total ICI patients in the US in 2026 estimated at ~300k and ~3M worldwide). Current standard of care treats Grade 2 or higher irEC requires halting life-extending cancer therapy and treatment with immunosuppressive systemic corticosteroids which carry risk of negative side Sources: Abu-Sbeih et al, Journal for ImmunoTherapy of Cancer, 2019; Braun et al, Trends in Cancer, 2025 Guggenheim Securities Flash Report issued 12/16/24, ICI Market analysis 2024, Grandview Research, Inc; IQVIA Institute Global Oncology Trends 2025
A significant unmet need exists for new therapies that prevent or treat irEC without immunosuppression and that preserve life-extending checkpoint inhibitor therapy Oral treatment that prevents or resolves irEC without systemic immunosuppression and without a negative impact on immune checkpoint inhibitor therapy Addresses the underlying gastrointestinal mucosal epithelial barrier dysfunction and inflammation associated with immune checkpoint inhibitor induced irEC Enables patients to continue life-extending immune checkpoint inhibitor therapy SER-155, an investigational live biotherapeutic, can uniquely address the upstream drivers of mucosal epithelial barrier dysfunction and inflammation without systemic immunosuppression -- Potential to address unmet needs and limitations of current standard of care
SER-155 has the potential to become a critical component of cancer care — Reduce toxic side effects, preserve anti-tumor immunity, and enable patients to continue ICI therapy Top-Line Results Summary: SER-155 resulted in immunosuppressive-free clinical response with mechanistic biomarker data supporting efficacy outcomes Efficacy 80% Immunosuppressive-free clinical response at Day 15 (primary endpoint) Safety Well-tolerated with No Drug related Serious Adverse Events (SAEs) identified Drug Pharmacology Improved GI mucosal epithelial barrier and reduced inflammation; clinical translation of SER-155’s unique mechanisms of action in additional patient population Memorial Sloan Kettering Cancer Center (MSK) investigator sponsored trial in cancer patients with immune checkpoint inhibitor-related enterocolitis (irEC; n=15)
MSK initiated trial to evaluate safety and efficacy of SER-155, an investigational biotherapeutic optimized to specifically target the type of damage caused by ICIs Memorial Sloan Kettering Cancer Center (MSK) Trial Summary -- NCT06801067 Grade 2-3 irEC 15 participants who had not yet received immunosuppressive therapy (corticosteroids and/or biologics) for irEC All participants had prior ICI treatment Treatment Phase 1st line treatment for irEC Oral and convenient: 2 days vancomycin conditioning followed by 12 days SER-155 (2 capsules taken once daily) Clinical Response Assessment Immunosuppressive-free response in diarrhea (primary symptom of irEC) at Study Day 15 Immunosuppressive-free response at Study Day 43 Safety through 180 days Drug Pharmacology SER-155 strain GI colonization; i.e., engraftment (PK) Mucosal epithelial barrier integrity (GI biomarker) Anti-inflammatory (GI & systemic biomarkers)
SER-155 efficacy response occurred in a cancer patient population representative of current clinical practice, spanned multiple ICI and cancer types Multiple cancer types Majority with stage 3-4 Multiple ICI types used on study: PD-1 inhibitors (Keytruda, Opdivo, Zynz), PD-L1 inhibitors (Imfinzi, Bavencio), CTLA-4 inhibitors (Yervoy, Imjudo), LAG-3 inhibitors (Opdualag), and combinations thereof All ICIs include irEC as an adverse reaction in their labels irEC with Grade 2-3 diarrhea 60% of participants with Grade 3 Excellent SER-155 dosing compliance: >99% 93% participants with ICI cancer therapy interrupted at entry Profile of 15 participants enrolled
Immune checkpoint inhibitor-related enterocolitis (irEC) is a significant side effect which can cause interruption of ICI cancer therapy and use of immunosuppressives Grade 1 Grade 2 Grade 3 Grade 5 Grade 4 Grade Diarrhea Treatment Guidelines Increase of <4 stools/day over baseline irEC increasing severity; patient population is substantial and growing Increase of 4-6 stools/day over baseline, trouble managing ‘day-to-day’ tasks Increase of ≥7 stools/day over baseline; limiting self-care Life-threatening Death Symptomatic care (i.e. loperamide) and continue ICI Halt ICI therapy Initiate systemic corticosteroids Halt ICI therapy Initiate high dose systemic corticosteroids & biologics irEC patients can experience severe diarrhea, abdominal pain, bloody stool, inflammation, colitis and hospitalization Moderate-to-Severe Population
SER-155 Top Line Efficacy: 80% of participants achieved immunosuppressive-free response at Day 15, with 33% of participants achieving complete clinical remission Day 15 Immunosuppressive-Free Response (Primary Endpoint; n=15) 80% 80% of all participants achieved Response 33% of all participants achieved Remission (Grade 0) Grade 0: 5 of 12 participants Grade 1: 7 of 12 participants Speed of Response: 11 of 12 responders were improving by Day 8 Magnitude of Response: 8 of 12 responders improved ≥ 2 grades by Day 15 Response: diarrhea decrease by one or more Grades Remission: Grade 0 (no diarrhea)
At Day 43, patients with a primary endpoint response at Day 15, had same grade or better Response = diarrhea decrease by ≥ 1 Grade; Remission = Grade 0 (no diarrhea) Secondary Endpoint: 5 of 15 participants maintained immunosuppressive-free response (2 in remission at Grade 0; 3 at Grade 1) 7 of 15 maintained response but received non-systemically acting, gastrointestinal-targeted immunosuppressives for mild residual or moderate recurrent symptoms The 12 of 15 participants who achieved Grade 0 or Grade 1 without immunosuppressives at Day 15 following SER-155 dosing achieved the same grade or better at Day 43
SER-155 Safety through Day 43: Generally well-tolerated with no treatment-related severe adverse events (SAEs) Majority of participants (73.3%) experienced a TEAE, most mild to moderate Most common: diarrhea (26.7%), though diarrhea is the primary symptom associated with irEC 4 events were assessed by investigator as possibly related to both vancomycin and SER-155, all moderate in severity and all resolved No participants experienced a TEAE leading to treatment or study discontinuation 2 of 15 (13.3%) participants experienced an SAE: none assessed as related to SER-155 (no SUSARs) Most common SAE SOCs: Gastrointestinal disorders (1); Cardiac disorders (1) No deaths through Day 43; 1 death* after Day 180, considered not related to SER-155 No drug-related AESIs^ No SER-155 species were identified in culture from any participant * One participant had a fatal cardiac arrest, assessed as unrelated to SER-155, before they could complete their final study follow up visit. ^ One participant had an AESI (BSI) at Day 136, assessed as unrelated to SER-155 Treatment-Emergent Adverse Events (TEAEs) Serious Adverse Events (SAEs) Adverse Events of Special Interest (AESIs)
Pharmacology: Biomarkers support SER-155 repaired mucosal epithelial barrier & reduced GI inflammation consistent with drug’s design & clinical results Participants show high levels of gastrointestinal (GI) inflammation with a subset also showing evidence of epithelial barrier damage prior to treatment Combined with clinical response rates, consistent directional improvement across both measures indicates an encouraging treatment effect on immune checkpoint inhibitor induced irEC disease activity Pharmacokinetics Pharmacodynamics SER-155 strains colonized participants' GI tracts, i.e., engrafted, with the majority of strains observed across the study participants with kinetics, magnitude, and durability comparable to that observed in prior Seres clinical studies Biomarkers of GI inflammation (fecal calprotectin) and epithelial barrier damage (fecal albumin) were elevated in participants indicating epithelial barrier disruption and high gut inflammation at baseline with concordant reductions after SER-155 dosing with significant (p < 0.05) reductions in both measures achieved by Day 43
SER-155 irEC Path Forward: Planning FDA engagement to discuss clinical development program for prophylaxis of irEC Unmet medical need with strong economics Advancing the irEC Prophylaxis Program Prevention approach addresses unmet medical need and aims to keep patients on immune checkpoint inhibitors (ICI) therapy and avoid immunosuppressive irEC treatments Efficient clinical development path (cost/timeline to approval) Enrollment risk enhancement approach for CTLA-4 containing regimens (highest irEC risk) while still enrolling all ICI types and regimens; potential for broad ICI reach Prophylactic dosing optimization expected to be included in FDA engagement strategy Primary and Secondary KOL and market research results confirmed that prophylaxis approach of SER-155 in irEC represents a multi-billion dollar opportunity Physicians’ favorable adoption rates (>75%) based on SER-155 target product profile (TPP) Biologics and Prevymis provide reasonable pricing analogues There is currently no SOC for prophylaxis of irEC irEC is a clinically significant adverse reaction and present in the approved labels of all ICI treatments, and significant market growth factors are present
SER-155 irEC study results are clinically meaningful and represent an additional valuable oncology indication Immune checkpoint inhibitors have revolutionized cancer treatment and represent a sizable market (2025 revenues) Well over $50B [KEYTRUDA, OPDIVO, YERVOY, IMFINZI, others] ~15% projected CAGR through early 2030's 11 Drug Approvals across 20+ solid tumor types (e.g., lung, melanoma, colorectal, etc.) Immune checkpoint inhibitors can cause irEC that can interrupt life-saving cancer treatment Moderate-to-Severe irEC occurs in ~25% of ICI treated patients and disrupts cancer treatment Up to 50% of ICI patients can experience irEC Unmet clinical needs irEC prophylaxis to prevent disruption of cancer therapy and non-immunosuppressive treatment to avoid negative impacts on treatment SER-155 has the potential to become a critical component of cancer care across multiple indications Achieved 80% immunosuppressive-free response & well-tolerated Potential utility of SER-155 to address unmet needs in multiple oncology areas Pharmacology data support broad potential of Seres novel live biotherapeutics
SER-603 Inflammatory Bowel Disease (IBD) --- Targeting inflammatory drivers of IBD that current standards of care cannot
Key challenges in IBD suggest new solutions are needed Efficacy ceiling experienced by many patients due to non-response or poor durability of response (see figure) Safety concerns limit the potential for combining advanced therapies that are immunosuppressive Current therapies don’t directly target the mucosal epithelial barrier, a critical target for limiting inflammation Patient heterogeneity in IBD patients is a core challenge and key reason many drugs don’t work or lack durability. Disrupted gut microbiome function is a major driver of IBD heterogeneity, pathogenesis, and nonresponse to advanced therapies UC Crohn’s Placebo SER-603 offers an effective, safe approach to address these gaps
Biomarker Validation: Identified bacterial features can predict response to therapy in clinical datasets 8% of Seres biomarker (+) patients experience remission, suggesting patients that have an inflammatory microbiome are very unlikely to respond to Ustekinumab, and may be candidates for combination therapy. 68% of Seres Biomarker (-) patients experience remission suggesting patients that do NOT have an inflammatory microbiome are more likely to respond to ustekinumab. Selection of Biomarker (-) patients increases remission after ustekinumab 50% of CD patients remit after ustekinumab in each cohort ~30% of patients Biomarker (+) Inflammatory microbiome ~70% of patients Biomarker (-) Non-inflammatory microbiome Seres Biomarker can predict response to therapy Wang et. al. 2025 - significant impact of microbiome on ustekinumab efficacy Selection of Biomarker (+) patients identifies patients for combination therapy
Monotherapy Proof of Concept: SER-603 addresses microbiome-driven inflammation in preclinical disease models of IBD Th1 cells Th17 cells SER-603 intervention reduces fecal lipocalin from inflammatory microbiome SER-603 intervention reduces Th1 and Th17 CD4+ T cells * ** Biomarker-based inflammatory microbiome Inflamm. Microbiome + SER-603 Biomarker-based inflammatory microbiome Inflamm. Microbiome + SER-603 GF IL10-/-mice Biomarker (+) microbiome test article ~4-5 weeks of colonization Evaluate treatment effect of SER-603 to address inflammatory microbiome SER-603: LBP designed to treat IBD SER-603 intervention SER-603 only Oral SER-603 intervention
Combination Therapy Proof of Concept: SER-603 increases the efficacy of anti-TNF�� therapy in a preclinical model of microbiome-driven inflammation GF IL10-/-mice Biomarker (+) microbiome test article ~4-5 weeks of colonization Evaluate treatment effect of SER-603 in combination with anti-TNF�� to address disease driven by inflammatory microbiome SER-603 & Anti-TNF�� SER-603 + anti-TNF�� is superior to anti-TNF�� alone in reducing lipocalin SER-603 + anti-TNF�� is superior to anti-TNF�� alone in reducing Th1 and Th17 CD4+ T cells SER-603 + anti-TNFa intervention SER-603 alone (negative control) Anti-TNFa only Mice randomized and anti-TNFa ± SER-603 intervention started next day Th1 cells Th17 cells * * * ** * ***
SER-603 holds the potential to address challenge of inadequate response in IBD patients as well as benefit patients earlier Well-tolerated safety profile and oral delivery creates potential for SER-603 to target mild-moderate patients as Monotherapy or add-on to 5-ASA Novel and complementary mechanism of action for combo with advanced therapies to convert partial or non-responders to remitters and expand durability of response without increased safety concerns IBD Tx algorithm ~30% of UC patients are either “smoldering”, (on 5-ASA and suffering silently), supplementing 5-ASA treatment with corticosteroids, or switching to immunomodulators and would be appropriate for an LBP instead “The biologics are a big step up for a lot of moderate patients, it would be nice to have a safe oral treatment that fills the space before a biologic”- UC KOL Many advanced therapies exhibit an efficacy ceiling and lack durability of response, instead of switching to another biologic, adding an LBP has the potential improve and extend efficacy
Seres continues on successful journey to lead on delivering on the therapeutic potential of live biotherapeutics (LBP) 2011 Seres founded by Flagship Pioneering 2015 SER-109 Breakthrough Therapy Designation -- Seres goes public $133M IPO (MCRB) 2023 SER-109 FDA approval and launch* -- 2020 SER-109 positive Phase 3 topline -- 88% sustained clinical response rate CDI recurrence up to 8 weeks 2024 SER-155 positive Phase 1b topline and Breakthrough Therapy Designation -- 77% relative risk reduction in bloodstream infections Seres has delivered an approved drug and additional clinical candidates in a novel therapeutic modality that address diseases in an innovative way SER-109 (VOWST) Phase 3 efficacy RESEARCH LETTER SER-109 (VOWST) Phase 3 durability Reduced antibiotic resistance gene carriage 2025-26 High profile publications on VOWST & SER-155 MoA VOWST mechanism of action SER-155 Phase 1b allo-HCT efficacy 2026+ Advance SER-155 allo-HCT and leverage clinical translation of novel MoAs to advance Inflammatory & Immune disease pipeline Differentiated Biotherapeutics platform SER-155 mechanism of action (in review)
THANK YOU