Seres Therapeutics — Third Quarter 2026 Earnings Summary

Financial Performance:

• Reported a net loss of $16.3 million for the third quarter of 2026, compared to net income of $8.2 million in the same period of 2025.
• Total revenue for the quarter was $593,000, up from $351,000 in the prior year period, driven by grant revenue.
• Research and development expenses were $5.6 million for the quarter, a decrease from $12.6 million in the prior year period, attributed to lower facilities costs, transition services agreement costs, personnel expenses, and SER-155 activities.
• General and administrative expenses were $5.4 million for the quarter, down from $9.5 million in the prior year period, due to reductions in personnel, facilities, and IT costs.
• Recorded a $5.7 million non-cash impairment of assets charge related to the early termination of the lease at 200 Sidney Street.
• Cash and cash equivalents totaled $17.5 million as of September 30, 2026, down from $45.8 million at December 31, 2025.
• Total assets were $65.9 million as of September 30, 2026, compared to $138.2 million at December 31, 2025.
• Total liabilities were $44.5 million as of September 30, 2026, compared to $94.0 million at December 31, 2025.
• Accumulated deficit increased to $(1,004,021,000) as of September 30, 2026, from $(972,403,000) at December 31, 2025.

Guidance and Future Outlook:

• Expects to submit plans for the next irEC study design to the FDA in the first quarter of 2027.
• Anticipates funding operations through the first quarter of 2027 based on currently available cash resources, including a $12.5 million payment received from Nestlé in October.
• The cash runway projection excludes proceeds from potential future partnerships or other capital sources.
• Early termination of the Cambridge, MA lease is expected to eliminate obligations as of December 31, 2026, and reduce ongoing facility-related cash costs beginning in 2027.

Business Segments and Product Lines:

• SER-155 (irEC): Plans to advance SER-155 into a next study evaluating prophylactic oral administration in patients initiating immune checkpoint inhibitor (ICI) therapy, including a dose optimization component. The study builds on investigator-sponsored trial (IST) results where 12 of 15 participants (80%) with moderate-to-severe irEC achieved an immunosuppressive-free clinical response at Day 15.
• SER-155 (Allo-HCT): Remains Phase 2 ready for the prevention of bloodstream infections in adults undergoing allogeneic hematopoietic stem cell transplant (allo-HCT), pending funding. The program holds Breakthrough Therapy and Fast Track designations.
• SER-428: Development is progressing for an investigational oral liquid formulation for patients who cannot take oral capsules, including critically ill patients in the Medical Intensive Care Unit (MICU). A Phase 1b open-label trial is being designed in collaboration with Columbia University and CARB-X, pending funding.
• SER-603: Advancing IND-enabling activities for inflammatory bowel disease (IBD) and engaging potential collaborators for clinical advancement.
• Published results from the Phase 1b clinical study of SER-155 in allo-HCT patients in Nature Medicine on November 3, reporting a 77% relative risk reduction in bloodstream infections compared with placebo.

Market and Competitive Landscape:

• Immune checkpoint inhibitors (ICIs) represent a worldwide market valued at well over $50 billion in 2025.
• Approximately 300,000 patients in the U.S. are currently on ICIs, representing a potential multi-billion-dollar commercial opportunity for SER-155 as a preventative treatment.
• irEC affects up to 50% of ICI recipients, with rates varying by ICI type and regimen.
• Current standard of care for Grade 2 or worse irEC requires halting ICI therapy and initiating systemic immunosuppressive corticosteroids, which carry toxicities and may compromise anti-cancer effects.

Risks and Challenges:

• The company has incurred significant losses, is not currently profitable, and may never become profitable.
• There is a continued need for additional funding to advance programs, particularly for SER-155 (allo-HCT), SER-428, and SER-603.
• Cost reduction actions may not achieve their intended benefits, including extending the cash runway.
• The company faces risks related to its ability to continue as a going concern and its limited operating history.
• Potential challenges include the failure to satisfy continued listing rules from The Nasdaq Stock Market LLC, reliance on third parties for clinical trials and manufacturing, and the ability to protect intellectual property.
• Actual results may differ from forward-looking statements due to factors such as competition, market acceptance, and regulatory disruptions.

Management Commentary and Tone:

• Richard Kender, Executive Chairman and Interim CEO, stated that the irEC IST provided promising evidence that SER-155 improved epithelial barrier integrity and reduced inflammation without systemic immunosuppression.
• Management determined that developing SER-155 to prevent irEC addresses a significant unmet clinical need and offers a time and capital-efficient path to clinical data.
• The company expressed confidence in its two oncology-focused programs for SER-155 and continues to seek capital through partnerships to advance these initiatives.
• Management highlighted the potential for SER-155 to enable ICI patients to remain on life-saving therapy by reducing the occurrence of irEC.

Other Key Points:

• Received the second of two $12.5 million payments related to the buy-out of potential future VOWST net sales-based milestones from Nestlé Health Science in October.
• Entered into an agreement on July 31 to terminate the lease for its facility at 200 Sidney Street in Cambridge, MA.
• Will present a poster highlighting IST results at the Society for Immunotherapy of Cancer (SITC) 2026 Annual Meeting in Phoenix, AZ, on November 7, 2026.
• The VOWST business was previously sold to Nestlé, with a $25 million installment payment recognized as a Gain on Sale in the third quarter of 2025.
• Weighted average common shares outstanding were 9,982,031 for the basic calculation in the third quarter of 2026.