Seres Therapeutics Presents SER-155 Study Data at ESCMID Congress
Seres Therapeutics announced three presentations at the 2026 European Society of Clinical Microbiology and Infectious Diseases, ESCMID, global congress, taking place April 17-21 in Munich, Germany. A poster presentation by Seres highlighted biomarker and clinical pharmacology data from the Company's Phase 1b study of SER-155, evaluating changes in gastrointestinal microbiome composition following administration in patients undergoing allogeneic hematopoietic cell transplantation. Data showed that administration of SER-155 induced a significant and durable shift in GI microbiome composition relative to placebo, characterized by high SER-155 species relative abundance. This shift is associated with improved GI epithelial barrier integrity that could reduce the likelihood of bacterial translocation from the GI to the bloodstream. In contrast, placebo-treated participants showed low abundance of SER-155 species and related Firmicutes, high abundance of Bacteroidetes, and a compromised GI epithelial barrier. These findings are consistent with the intended mechanisms of action of SER-155, including protection of the GI epithelial barrier, and align with previously reported clinical observation of reduced incidence of bloodstream infections in SER-155-treated patients following allo-HCT.
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- Earnings Highlights: Seres Therapeutics reported a FY GAAP EPS of $0.64 and revenue of $0.78 million, indicating ongoing growth potential in the microbiome therapeutics sector, although overall revenue remains modest.
- Cash Position: As of December 31, 2025, Seres had $45.8 million in cash and cash equivalents, including $12.2 million raised through its at-the-market equity offering in Q4 2025, providing a solid foundation for future operations.
- Operational Funding Outlook: Based on its current cash position and operational plans, Seres expects to fund its operations through the third quarter of 2026, demonstrating effective cash management, although further opportunities to extend its cash runway are being evaluated.
- Strategic Direction Reevaluation: Following a pause in investments for its lead program, Seres is reassessing its strategic direction; despite facing dilution risks, the company is actively exploring the potential of its microbiome therapeutics platform to achieve greater market breakthroughs in the future.
- Executive Changes: Seres Therapeutics announced the appointment of Richard Kenderas as Executive Chair and interim CEO, who has been on the board since September 2014, suggesting his extensive experience will guide the company's strategic direction.
- Management Stability: Former co-CEOs Thomas DesRosier and Marella Thorell will continue as Chief Legal Officer and Chief Financial Officer, respectively, ensuring continuity and stability in management, which is crucial for maintaining investor confidence.
- Investment Pause Impact: Following the pause in investments for its lead program, Seres faces market concerns regarding its future growth potential, leading to a decline in stock price, reflecting investor caution towards the company's strategic adjustments.
- Market Reaction: Despite strong SER-155 data, the increased dilution risk has prompted analysts to adjust Seres' rating to 'Hold', which may affect the company's future financing capabilities and market performance.
- Investment Pause: Seres Therapeutics announced a pause on additional investments for its mid-stage trial, resulting in a ~25% drop in premarket trading, indicating significant funding challenges for its lead asset SER-155.
- Focus on Early Programs: The company will shift its focus to earlier-stage programs, including a fully enrolled study for SER-155 in immune checkpoint-related enterocolitis, expected to generate data by early Q2 2026, highlighting potential market demand for cancer therapies.
- Layoff Plans: Seres plans to lay off nearly 30% of its workforce to extend its cash runway through Q3 2026, a move aimed at streamlining operations and reducing costs to support the development of its early-stage pipeline.
- Regulatory Preparedness: CEO Marella Thorell stated that the company has taken extensive steps to prepare for a robust SER-155 Phase 2 study, including submitting a final protocol to the FDA, demonstrating commitment and confidence in future research.
- Study Pause Reason: Seres announced the pause of the SER-155 Phase 2 study following the completion of site evaluation and qualification with its contract research organization, despite the drug substance already being manufactured, which could hinder future R&D progress.
- Strategic Shift: The company will refocus its operations on high-value early-stage pipeline programs, particularly those targeting inflammatory bowel disease (IBD), aiming to seek greater market opportunities amid limited resources.
- Cash Runway Extension: Through cost-cutting measures, including a 30% workforce reduction, Seres expects to extend its cash runway into Q3 2026, which will support the continued development of immune-related disease programs while seeking additional funding for the SER-155 Phase 2 study.
- Market Reaction: While retail sentiment on Stocktwits remains in the 'bullish' territory, MCRB stock has fallen 51% year-to-date and 75% over the past 12 months, indicating investor concerns about the company's future prospects.
- Strategic Shift: Seres Therapeutics announced a pivot towards emerging programs in inflammatory and immune diseases, resulting in a 16.25% drop in stock price during Thursday's premarket session, raising investor concerns about its current pipeline and funding strategies.
- Clinical Trial Update: The company has finalized the protocol for its Phase 2 study of SER-155 and is pausing further investment in this program, with results from the investigator-sponsored study expected in early Q2 2026, indicating a focus on early-stage programs.
- Workforce Reduction: Seres announced a 30% workforce reduction aimed at extending its cash runway through Q3 2026, allowing it to concentrate on advancing early-stage live biotherapeutic programs and pursue potential collaborations, highlighting financial constraints.
- Technical Trend Analysis: Currently trading at $11.80, Seres stock is 24.4% below its 20-day simple moving average, indicating a bearish trend and ongoing operational challenges, as the stock has decreased by 13.86% over the past 12 months.









