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Seres Therapeutics Investor Presentation May 2025 Disclaimers 2 Seres Therapeutics, Inc. © 2025 2 Transforming patient outcomes using proprietary consortia of live biotherapeutics Strong Foundation 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 s ...

Financial Data and Key Metrics Changes - The company reported a net income from continuing operations of $32.7 million in Q1 2025, compared to a net loss of $32.9 million in Q1 2024, primarily driven by a $50 million installment payment received from Nestle [15][16] - Research and development expenses decreased to $11.8 million from $19.5 million in the same quarter last year, reflecting lower personnel expenses and reduced costs related to the SER-155 Phase Ib study [16] - General and administrative expenses were $11.9 million, down from $14.9 million in Q1 2024, primarily due to lower personnel and contractor expenses [16] - As of March 31, 2025, the company had cash and cash equivalents of $58.8 million, with an expected second installment payment of approximately $23.5 million from Nestle in July 2025 [16][17] Business Line Data and Key Metrics Changes - SER-155 remains the top corporate priority, with significant progress towards initiating the next clinical study, following a Phase 1b study that showed a 77% relative risk reduction in bloodstream infections compared to placebo [5][6] - The Phase 1b study also demonstrated a favorable safety profile consistent with historical data across the live biotherapeutic product platform [6] Market Data and Key Metrics Changes - The company received positive feedback from the transplant community at the European Society for Blood and Marrow Transplantation Conference, emphasizing the need for new approaches to prevent bloodstream infections [7][8] - The SER-155 poster received the best clinical poster award, validating the patient need and the scientific rigor of the study [9] Company Strategy and Development Direction - The company aims to develop SER-155 and other live biotherapeutics to prevent infections in various patient groups, including allo HSCT, autologous HSCT, cancer patients with neutropenia, and solid organ transplant recipients [12] - The strategic focus includes addressing gut-related inflammatory and immune diseases such as IBD, with an emphasis on the compromised gut epithelial barrier as a core component of underlying pathology [12] Management's Comments on Operating Environment and Future Outlook - Management expressed confidence in the constructive interactions with the FDA, which have been regular and supportive, particularly due to the breakthrough therapy designation for SER-155 [36] - The company is actively exploring partnerships to secure financial support and maximize the clinical and commercial value of SER-155, given the challenging biotech financing environment [12][17] Other Important Information - A one-for-20 reverse stock split was executed, and the company regained compliance with NASDAQ's bid price requirement [17] - The company is prioritizing activities that advance clinical and strategic goals while preserving cash [17] Q&A Session Summary Question: Are partnership discussions gated by progress around SER-155? - Management indicated that securing a partnership is a key long lead time item for moving forward with the study, while they are advancing other necessary preparations [24][25] Question: Can you outline the proposed powering assumptions for the Phase II study? - Management stated that the powering included in the design will allow data from this study to be used for both efficacy and safety components for FDA submission [27][28] Question: Have there been any large staffing changes at the FDA? - Management noted that their interactions with the FDA have been constructive and regular, and they are pleased with the feedback received [36] Question: Will the Phase II study be designed to evaluate overall survival? - The primary endpoint for the Phase II study is bloodstream infection reductions, with discussions ongoing regarding potential efficacy measures for Phase III [50][52]

Core Insights - Seres Therapeutics, Inc. will present three related posters at the 2025 Digestive Disease Week (DDW) Conference, highlighting advancements in live biotherapeutics for inflammatory and immune diseases [1][2] Company Developments - The company previously reported exploratory translational biomarker data from its SER-155 Phase 1b study, indicating its potential to enhance intestinal epithelial barrier integrity and modulate systemic inflammatory responses [2] - Seres is actively seeking partnership opportunities to further develop its biotherapeutics targeting inflammatory and immune diseases [3] Presentation Details - The first presentation will focus on the characterization of IBD microbiomes to evaluate candidate biomarkers for patient selection, scheduled for May 3, 2025 [4] - The second presentation will discuss candidate biomarkers of microbiome disruption for patient selection in clinical trials of microbiome therapeutics in ulcerative colitis, also on May 3, 2025 [4] - An encore presentation will cover pharmacokinetic and pharmacodynamic results from a Phase 1b study of SER-155 in adults undergoing allo-HCT, set for May 4, 2025 [5] Industry Context - The Digestive Disease Week (DDW) is a significant international event in gastroenterology, showcasing nearly 6,000 abstracts and over 1,000 invited talks on the latest advances in GI research, medicine, and technology [5]