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)

SER-155 development remains dependent on funding as Seres expects available resources to support operations through Q1 2027.

Rhea-AI Summary

Seres Therapeutics (Nasdaq: MCRB) reported a third-quarter net loss of $16.3 million and outlined plans for a SER-155 prevention study. The loss compares with $8.2 million net income a year earlier, when results benefited from a VOWST sale payment. Seres expects to submit the study design to the FDA in Q1 2027 to evaluate prevention of immune checkpoint inhibitor-related enterocolitis, or irEC, an intestinal inflammatory reaction to cancer therapy. Development depends on funding.

In an open-label treatment trial, 12 of 15 participants achieved an immunosuppressive-free diarrhea response at Day 15; no serious adverse events were attributed to SER-155. Quarterly research and administrative expenses declined. Cash was $17.5 million at September 30, followed by a $12.5 million Nestlé payment in October. Seres expects these resources to fund operations through Q1 2027, excluding potential new capital.

21 points · 2 major

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1 major · 9 points

Hollow bars mark forward-looking points. How the balance works

Positive

• Major pointSER-155 treatment trial achieved its primary endpoint in 12 of 15 participants (80%) at Day 15.
• Major pointNestlé's second $12.5 million payment for the VOWST milestone buyout was received in October. 63% of market cap
• Moderate pointImmunosuppressive-free complete clinical remission occurred in five of 15 participants (33%) at Day 15.
• Moderate point. Forward-looking: it has not happened yet and may not happen.Seres expects to submit its SER-155 irEC prevention study design to the FDA in Q1 2027.
• Moderate pointSER-155 allo-HCT study showed a 77% relative risk reduction in bloodstream infections versus placebo.
• Moderate point. Forward-looking: it has not happened yet and may not happen.Facility lease termination materially eliminates obligations from December 31, 2026, reducing facility cash costs beginning in 2027.
• Moderate pointThird-quarter operating loss narrowed to $16.152 million from $22.477 million in 2025.

14 minor points

• Minor pointSER-155 was generally well tolerated through Day 43, with no related serious adverse events.
• Minor pointGastrointestinal inflammation and intestinal barrier biomarkers improved, with statistically significant reductions by Day 43.
• Minor pointSER-155 has Breakthrough Therapy and Fast Track designations for bloodstream infection prevention in allo-HCT.
• Minor pointSER-428 development has CARB-X grant support; Seres is designing a Phase 1b sepsis trial.
• Minor pointSER-603 activities needed before human trials continue, with Seres seeking collaborators for inflammatory bowel disease development.
• Minor pointThird-quarter grant revenue rose to $593,000 from $351,000 in 2025.
• Minor pointThird-quarter research and development expenses fell to $5.592 million from $12.616 million in 2025.
• Minor pointThird-quarter general and administrative expenses fell to $5.448 million from $9.476 million in 2025.
• Minor pointThird-quarter manufacturing services expenses fell to zero from $736,000 in 2025.
• Minor pointNine-month grant revenue rose to $1.687 million from $351,000 in 2025.
• Minor pointNine-month research and development expenses fell to $27.928 million from $37.376 million in 2025.
• Minor pointNine-month general and administrative expenses fell to $20.579 million from $31.617 million in 2025.
• Minor pointNine-month manufacturing services expenses fell to zero from $5.952 million in 2025.
• Minor pointNine-month operating loss narrowed to $58.332 million from $74.594 million in 2025.

Negative

• Major pointThird-quarter net loss was $16.3 million versus $8.2 million net income in 2025, primarily reflecting prior-year VOWST proceeds.
• Moderate pointCash and equivalents declined to $17.528 million at September 30, 2026 from $45.766 million at December 31, 2025.
• Moderate point. Forward-looking: it has not happened yet and may not happen.Seres expects resources, including October's payment, to fund operations only through Q1 2027, excluding potential new capital.
• Moderate point. Forward-looking: it has not happened yet and may not happen.SER-155 irEC prevention development is dependent on funding, with FDA study-design feedback still ahead.
• Moderate point. Forward-looking: it has not happened yet and may not happen.SER-155 bloodstream infection prevention is Phase 2 ready, pending funding.

4 minor points

• Minor point. Forward-looking: it has not happened yet and may not happen.SER-428 further clinical development remains pending funding from grants or other sources.
• Minor pointThird-quarter lease-related asset impairment was a $5.705 million non-cash charge.
• Minor pointNine-month asset impairment charges totaled $11.512 million, versus none in 2025.
• Minor pointSER-155 irEC evidence comes from an open-label treatment trial, rather than the planned prevention study.

News Explained

Reported common shares outstanding rose from 9,556,466 at December 31, 2025, to 10,049,501 at September 30, 2026, reducing each unchanged holding's fraction of the total.

Seres reports that its July 31 agreement to terminate the 200 Sidney Street lease materially eliminates its obligations under that lease as of December 31, 2026, and reduces ongoing facility cash costs beginning in 2027.

Key Figures

Net loss: $16.3 million Research and development expenses: $5.6 million General and administrative expenses: $5.4 million +4 more

Net loss

$16.3 million

Third quarter 2026; compared with net income of $8.2 million in Q3 2025

Research and development expenses

$5.6 million

Third quarter 2026; compared with $12.6 million in Q3 2025

General and administrative expenses

$5.4 million

Third quarter 2026; compared with $9.5 million in Q3 2025

Cash and cash equivalents

$17.5 million

As of September 30, 2026

Expected cash runway

Through the first quarter of 2027

Includes the $12.5 million Nestlé payment received in October

Immunosuppressive-free clinical response

12 of 15 participants (80%)

SER-155 IST; response assessed at Day 15

FDA study-design submission

First quarter of 2027

Planned SER-155 irEC study

Key Terms

immune checkpoint inhibitor, investigator-sponsored trial, enterocolitis, fast track designation, +1 more

5 terms

immune checkpoint inhibitor medical

"immune checkpoint inhibitor (ICI) cancer therapy"

An immune checkpoint inhibitor is a type of medicine that helps the body's immune system recognize and attack cancer cells more effectively. It works by blocking certain signals that cancer uses to hide from immune defenses, allowing the immune system to target tumors. This breakthrough has led to new cancer treatments, making immune checkpoint inhibitors an important area of growth and innovation in the healthcare industry.

investigator-sponsored trial medical

"investigator-sponsored trial (IST) conducted at Memorial Sloan Kettering Cancer Center"

An investigator-sponsored trial is a clinical study that is designed, run and overseen by a doctor or research team at a hospital or university rather than by a drug or device company. For investors it matters because such trials can provide independent tests of a treatment’s benefits or risks, like a third-party review, and can affect a product’s perceived value, regulatory path and future revenue potential without the company bearing full control or cost.

enterocolitis medical

"immune checkpoint inhibitor-related enterocolitis (irEC)"

Enterocolitis is inflammation or infection affecting the small intestine and colon, causing symptoms like abdominal pain, diarrhea, fever and sometimes dehydration; think of it as the gut becoming irritated and swollen like a clogged, leaking pipe. For investors, it matters because cases linked to a drug, device or procedure can lead to patient harm, trial delays, recalls, higher costs or regulatory scrutiny, which can affect a company’s earnings and stock value.

fast track designation regulatory

"received Breakthrough Therapy and Fast Track designations"

Fast track designation is a status the U.S. Food and Drug Administration grants to drugs intended to treat serious conditions and address an unmet medical need. It gives the developer more frequent communication with the FDA and can allow parts of the application to be reviewed on a rolling basis, and it may pave the way to priority review or accelerated approval. It can shorten development timelines, though it does not guarantee approval.

ind-enabling regulatory

"continues to advance IND-enabling activities for SER-603"

Ind-enabling describes the preclinical tests and safety work a drug candidate must pass before a company can ask regulators for permission to start human trials (an Investigational New Drug or IND filing). Think of it as the mechanical inspection and crash-testing a prototype car needs before it can legally be driven on public roads; for investors, successful ind-enabling work reduces technical and regulatory risk and makes clinical progress and potential value creation more likely.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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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., Nov. 04, 2026 (GLOBE NEWSWIRE) -- 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,				December 31,
		2026				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

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did the Seres MCRB SER-155 enterocolitis trial show?

In the open-label treatment trial, 12 of 15 participants (80%) achieved an immunosuppressive-free clinical response at Day 15. The primary endpoint required at least a one-grade improvement in diarrhea without immunosuppressive therapy. Five of 15 participants (33%) achieved complete clinical remission without immunosuppressive therapy at Day 15.

How long does Seres MCRB expect its cash to last?

Seres expects available resources to fund operations through the first quarter of 2027. That estimate includes $17.5 million in cash and cash equivalents at September 30, 2026, and the $12.5 million Nestlé payment received in October. It excludes proceeds from potential future partnerships or other capital sources.

How does Seres plan to select dosing for its SER-155 prevention study?

Seres plans to seek FDA feedback on dose optimization that could include a healthy volunteer study component or a dosing lead-in. Results are expected to inform the preventive dosing course before dosing begins in the broader population starting immune checkpoint inhibitor therapy. Potential study endpoints include enterocolitis incidence, cancer immunotherapy administration and safety.