On May 5, 2026 Seres Therapeutics, Inc. (Nasdaq: MCRB), (Seres or the Company), a leading live biotherapeutics company, reported first quarter 2026 financial results and provided business updates.

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"We are approaching an important clinical milestone with the expected readout in the coming weeks from the investigator-sponsored study at Memorial Sloan Kettering Cancer Center, an institution with whom we’ve collaborated for over a decade, evaluating SER-155 in immune checkpoint inhibitor-related enterocolitis (irEC)," said Richard Kender, Executive Chair and interim Chief Executive Officer of Seres. "irEC is a serious condition which represents a meaningful therapeutic and commercial opportunity, and with positive data we will evaluate potential development pathways and adjacent expansion opportunities. In parallel, we are advancing our inflammatory and immunology portfolio, including SER-603 for inflammatory bowel disease, with IND-enabling work progressing. We have achieved Phase 2 readiness for SER-155 for the prevention of bloodstream infections in patients undergoing allo-HSCT for the treatment of blood cancer and are seeking funding to commence the study. We are continuing disciplined capital allocation while actively pursuing partnerships and other financing sources to support Seres’ pipeline advancement and long-term value creation."

Recent Highlights

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As highlighted in recent press releases from February and March, Seres is prioritizing its emerging live biotherapeutic programs in inflammatory & immune (I&I) diseases, including SER-155 for immune checkpoint-related enterocolitis (irEC) and SER-603 for inflammatory bowel disease (IBD).

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Seres is collaborating with Memorial Sloan Kettering Cancer Center on an investigator-sponsored trial evaluating SER-155 in participants with irEC. irEC is among the most frequent and severe immune-related adverse events (irAEs) in recipients of immune checkpoint-inhibitor therapy and can be observed in up to 50% of patients, with rates varying based on cancer drug and treatment regimen. Study enrollment is complete, with 15 patients enrolled, and clinical data are expected in the coming weeks. Positive data from this IST could further inform the expansion of indications well-suited to Seres’ live biotherapeutic approach.

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The Company continues to advance its preclinical stage live biotherapeutic product candidates, including SER-603. The Company is conducting IND-enabling activities for SER-603 and is engaging potential collaborators to support the clinical advancement of this program as a mono and/or combination therapy for IBD.

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In May, Seres presented new preclinical data supporting the design and potential of SER-603 at Digestive Disease Week (DDW). The Company’s poster, titled "The Rational Design of SER-603: A Next Generation Cultivated Microbial Consortia to Treat IBD," which was selected as a DDW ‘Poster of Distinction,’ highlights Seres’ integrated approach to the design of microbiome therapeutics, combining rational strain selection and a novel biomarker-driven patient stratification.

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In May, Seres’ management will be attending Memorial Sloan Kettering’s (MSK) Innovation with Lasting Impact Summit which this year focuses on "Drug Discovery & Development and MSK" and will be presenting, along with Dr. Jonathan (Tsoni) Peled an oncologist at MSK specializing in bone marrow transplantation for blood cancers, on Seres’ decade-long research and clinical development collaboration with MSK.

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SER-155 is Phase 2 ready for the prevention of serious bloodstream infections in patients undergoing allogeneic hematopoietic stem cell transplants (allo-HSCT) for the treatment of blood cancer, and efforts to secure funding to advance clinical development for this program continue.

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Supported by a grant from CARB-X (Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator), a global nonprofit partnership accelerating the development of new antibacterial products to address drug-resistant bacteria, Seres is progressing development of an oral liquid formulation based on SER-155 strains, referred to as SER-428, for dosing in patients who cannot take oral capsules such as intubated patients in the medical ICU, and other medically vulnerable patients at high risk of AMR infections. Seres has advanced manufacturing of SER-428 and is designing a Phase 1b open label trial, in collaboration with Dr. Dan Freedberg at Columbia University, to evaluate this therapeutic candidate in medical ICU patients at high risk of infection.

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The Company attended the ESCMID Global Conference in April and presented a poster highlighting biomarker and clinical pharmacology data from the Company’s SER-155 Phase 1b study in allo-HSCT. Data showed that administration of SER-155 induced a significant and durable shift in gastrointestinal (GI) microbiome composition relative to placebo, characterized by high relative abundance of SER-155 species. This shift is associated with improved GI epithelial barrier integrity that could reduce the likelihood of bacterial translocation from the GI to the bloodstream. These pharmacology results are consistent with the intended SER-155 mechanisms of action as well as the observation of significantly lower bloodstream infection incidence (77% relative risk reduction) post allo-HSCT in SER-155-administered participants in Seres’ Phase 1b study.

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In January, the Company announced the publication of manuscripts in Nature Medicine and the Journal of Infectious Diseases, highlighting new insights into the functional mechanism and clinical impact of VOWST, which was developed by Seres and sold to Nestlé Health Science (Nestlé) in 2024. These publications further inform the continued development of Seres’ next-generation live biotherapeutics pipeline.

Financial Results

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Net loss was $19.9 million for the first quarter of 2026, compared to net income of $32.7 million for the same period in 2025. Contributing to the net income in the first quarter of 2025 was a $50 million installment payment received from Nestlé, related to certain transition services following the sale of VOWST and $6.3 million in reimbursements from Nestlé for the costs of those services. Operating expenses were approximately $6 million lower in the first quarter of 2026 compared to the first quarter of 2025.

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Research and development expenses were $13.2 million for the first quarter of 2026, compared with $11.8 million for the same period in 2025, primarily due to higher facilities and manufacturing-related costs that in 2025 were partially reimbursed by Nestlé under the transition services agreement (TSA), partially offset by lower personnel-related expenses.

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General and administrative expenses were $8.1 million for the first quarter of 2026, compared with $11.9 million for the same period in 2025, reflecting lower personnel and professional services costs, and a reduction in IT costs, including those related to services provided under the TSA.

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There were no manufacturing services expenses in the first quarter of 2026, compared with $3.5 million in the first quarter of 2025, as the Company completed such services, provided under the TSA, at the end of 2025.

Cash and Cash Runway

As of March 31, 2026, Seres had $29.8 million in cash and cash equivalents. Based on Seres’ current cash position and operating plans, the Company expects to fund operations through the third quarter of 2026. The Company continues to evaluate opportunities to extend its cash runway.

(Press release, Seres Therapeutics, MAY 5, 2026, View Source [SID1234665132])