Seres Therapeutics, Inc. · NASDAQ:MCRB
Seres Therapeutics — Investor Presentation (July 2026)
53 slides from Seres Therapeutics's investor presentation, July 2026
Slide 1: Seres Company Overview
Seres Company Overview July 2026 Seres Therapeutics, Inc. © 2026
Slide 2: Disclaimers
Disclaimers 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-looki
Slide 3: Seres continues on successful journey to lead in live biotherapeutics
Seres continues on successful journey to lead on delivering on the therapeutic potential of live biotherapeutics (LBPs) 2025-26 2024 High profile publications on SER-155 positive Phase VOWST & SER-155 MoA 1b topline and 2020 2023 Breakthrough Therapy 2026+ SER-109 positive Phase 3 SER-109 FDA approv
Slide 4: Focused strategy to advance novel live biotherapeutics and deliver shareholder value
Focused strategy to advance novel live biotherapeutics and deliver shareholder value • Considering the next phase of development of SER-155 in immune checkpoint–related enterocolitis (irEC), a serious adverse reaction to immune checkpoint inhibitor (ICI) therapy that forces many patients to halt the
Slide 5: Pipeline: Seres biotherapeutics target mucosal epithelial barrier-immune diseases
Pipeline: Seres biotherapeutics target mucosal epithelial barrier-immune associated infection and inflammatory diseases leveraging years of clinical progress and data Preclinical Ph1 Ph2 Ph3 Commercial • Clinical stage asset with positive Ph1b efficacy and safety data SER-155 • Breakthrough Therapy
Slide 6: Consortia of live commensal bacteria as biotherapeutics
Consortia of live commensal bacteria as biotherapeutics Clinical translation on targeting key drivers of disease Mucosal Epithelial Barrier-Immune Interface: • Protect and induce regeneration of epithelial barrier in the gastrointestinal tract • Regulate immune pathways to reduce GI inflammation and
Slide 7: Industry Leadership: Discovery to Approval
Seres has… Accessed Accessed the the vastpotential vast functional functional potentialofofyears of millions millions of years of of co-evolution co-evolution between between microbes andmicrobes andtotheir their hosts hosts prevent to treat and prevent and treat diseases diseases Industry Leadershi
Slide 8: Consortia of live commensal bacteria can be used as therapeutics
Consortia of live commensal bacteria can be used as therapeutics Live Biotherapeutics (LBP) Consortia of PK PD bacterial strains optimized to produce Disrupted Microbiome Engraftment Restructure Change in Change therapeutically active with functional of drug microbiome microbiome in host metabolites
Slide 9: Well tolerated safety profile reducing development risk
Seres’ biotherapeutics and pipeline candidates are expected to have well tolerated safety profile, reducing development risk ✓ Based on GI bacteria naturally found in healthy humans, and not associated with disease ✓ VOWST product profile includes well tolerated safety without drug-related serious a
Slide 10: Seres has full stack of live biotherapeutics platform capabilities
Seres has full stack of live biotherapeutics platform capabilities & experience in novel live biotherapeutic modality Demonstrated Novel Therapeutic GMP Field-leading Microbiome biomarker & Manufacturing & Quality drug target identification --- --- spans broad biological breadth with strains, metabo
Slide 11: MbTx platform: discovery and product optimization engine
MbTx platform: a discovery and product optimization engine, designed to mine and harness microbe-host functional interactions to address disease INPUTS Clinically actionable OUTPUTS Strain Library Novel Targets & Leads Seres' curated collection of bacteria that represent Therapeutically active strai
Slide 12: Manufacturing Platform
Manufacturing Platform: Delivers defined consortia in oral formulations using cost- effective production processes which reflect regulatory benchmarks for LBPs Strain isolation and characterization pipeline to rapidly identify cGMP- suitable medium components Highly intensive strain bioprocessing le
Slide 13: Prevention of pathogen epithelial barrier translocation & bloodstream infections (BSI): SER-155
Prevention of pathogen epithelial barrier translocation & bloodstream infections (BSI) SER-155 13 Seres Therapeutics, Inc. © 2026
Slide 14: SER-155 Oncology Infection: target product profile
SER-155 Oncology Infection: Protect mucosal epithelial barrier integrity and clinically reduce bloodstream & antimicrobial resistant infections in blood cancer patients Value Proposition Target Product Profile: Preventing Bloodstream Infections in Allo-HCT Transformational efficacy and placebo-like
Slide 15: Allo-HCT regimen can result in life-threatening complications
Allogeneic hematopoietic stem cell transplant (allo-HCT) regimen can result in life- threatening complications Allo-HCT treatment regimen Chemotherapy Allo-HCT • Only ~60% survival 3 years post- Anti-infectives infusion Increased risk of infection, GvHD transplant • Significant immune compromised pa
Slide 16: Bloodstream infections are a leading cause of death post-transplant
Bloodstream infections (BSIs) are a leading cause of death post-transplant and are increasing in incidence with uptake of PTCy treatment Bacterial BSI in first 30 days • BSI risk increasing due to recent adoption of post-transplant cyclophosphamide (PTCy) for post-HCT Incidence GvHD prophylaxis 50%
Slide 17: Physicians highly concerned about BSIs in allo-HCT patients
Infectious disease and hematology-oncology physicians are highly concerned about BSIs in allo-HCT patients; effective prophylaxis is a major unmet need HCPs have high level of concern Major unmet needs for BSIs for BSIs • Top need: effective prophylaxis – 1 2 3 4 5 6 7 current agents not seen as suc
Slide 18: SER-155 protects GI mucosal epithelial barrier and prevents BSIs
SER-155 protects GI mucosal epithelial barrier and prevents translocation of pathogens and BSIs BSI are associated with mucosal epithelial barrier-immune Seres allo-HCT BSI Program compromise GI Pathogen Domination • Received both Fast Track and Breakthrough Therapy Pro-inflammatory pathogens domina
Slide 19: Key Data: SER-155 Phase 1b reduction in bloodstream infections
Key Data: SER-155 Placebo-controlled Phase 1b reduction in bloodstream infections with mechanism of action (MoA) clinical translation Significant efficacy and placebo-like Substantial reduction in pathogen Rapid protection of epithelial barrier safety profile in Phase 1b study in domination in Phase
Slide 20: SER-155 is Phase 2 ready for allo-HCT patients
SER-155 is Phase 2 ready for patients undergoing allo-HCT to treat hematologic malignancies and design provides opportunity for adjacent indication expansion • Received Fast Track and Breakthrough Designation • FDA in agreement with Phase 2 study design Phase 2 • FDA open to expedited path to engage
Slide 21: SER-155 in allo-HCT commercial opportunity and indication expansion
SER-155 in allo-HCT commercial opportunity is meaningful and has indication expansion potential (10x addressable population) creating multi-billion dollar opportunity Broader leukemia & Allo-HCT Autologous HCT lymphoma population* WW annual diagnoses or ~40,000 ~60,000 ~500,000 transplants US annual
Slide 22: Viral prophylaxis provides precedent on commercial opportunity
Viral prophylaxis provides precedent on commercial opportunity in medically vulnerable patients Prevymis - increasingly used for viral infection prophylaxis (e.g., allo-HCT and solid organ transplant populations) • Allo-HCT is a very costly procedure (~$400K US year 1 allo-HCT per patient cost) $978
Slide 23: Immune Checkpoint Inhibitor-Related Enterocolitis (irEC)
Immune Checkpoint Inhibitor-Related Enterocolitis (irEC) SER-155 23 Seres Therapeutics, Inc. © 2026
Slide 24: SER-155 irEC: Treat immune-related enterocolitis from ICI therapies
SER-155 irEC: Treat immune-related enterocolitis (irEC) resulting from ICI therapies Value Proposition Target Product Profile: SER-155 for the treatment of irEC First-in-class microbiome therapeutic to treat Mechanism of Action immune checkpoint inhibitor-related enterocolitis Dosing / Route of Admi
Slide 25: What is Immune Checkpoint Inhibitor-Related Enterocolitis (irEC)?
What is Immune Checkpoint Inhibitor-Related Enterocolitis (irEC)? irEC is a serious, frequent complication of rapidly growing immune checkpoint inhibitor therapy that requires immunosuppressive treatment and often disrupts life-extending cancer treatment • Immune Checkpoint inhibitors (ICIs) activat
Slide 26: Significant unmet need for new therapies that treat irEC
A significant unmet need exists for new therapies that treat irEC without immunosuppression and that preserve life-extending checkpoint inhibitor therapy Oral treatment that resolves irEC without systemic immunosuppression and without a negative impact on immune checkpoint inhibitor therapy Enable p
Slide 27: Top-Line Results Summary: SER-155 immunosuppressive-free clinical response
Top-Line Results Summary: SER-155 resulted in immunosuppressive-free clinical response with mechanistic biomarker data supporting efficacy outcomes Memorial Sloan Kettering Cancer Center (MSK) investigator sponsored trial in 15 cancer patients with immune checkpoint inhibitor-related enterocolitis (
Slide 28: MSK initiated trial to evaluate SER-155
MSK initiated trial to evaluate safety and efficacy of SER-155, an investigational biotherapeutic optimized to specifically target the type of damage caused by ICIs Memorial Sloan Kettering Cancer Center (MSK) Trial Summary -- NCT06801067 • 15 participants who had not yet received immunosuppressive
Slide 29: SER-155 efficacy in representative cancer patient population
SER-155 efficacy response occurred in a cancer patient population representative of current clinical practice, spanned multiple ICI and cancer types Profile of 15 participants enrolled Multiple cancer types • Majority with stage 3-4 Multiple ICI types used on study: • PD-1 inhibitors (Keytruda, Opdi
Slide 30: irEC is a significant side effect interrupting ICI cancer therapy
Immune checkpoint inhibitor-related enterocolitis (irEC) is a significant side effect which can cause interruption of ICI cancer therapy and use of immunosuppressives irEC increasing severity; patient population is substantial and growing Moderate-to-Severe Population Grade 1 Grade 2 Grade 3 Grade 4
Slide 31: SER-155 Top Line Efficacy: 80% response at Day 15
SER-155 Top Line Efficacy: 80% of participants achieved immunosuppressive-free response at Day 15, with 33% of participants achieving complete clinical remission Day 15 Immunosuppressive-Free Response (Primary Endpoint; n=15) 80% of all participants achieved Response 80% 33% of all participants achi
Slide 32: At Day 43, responders had same grade or better
At Day 43, patients with a primary endpoint response at Day 15, had same grade or better The 12 of 15 participants who achieved Grade 0 or Grade 1 without immunosuppressives at Day 15 following SER-155 dosing achieved the same grade or better at Day 43 Secondary Endpoint: 5 of 15 participants mainta
Slide 33: SER-155 Safety through Day 43
SER-155 Safety through Day 43: Generally well-tolerated with no treatment- related severe adverse events (SAEs) • Majority of participants (73.3%) experienced a TEAE, most mild to moderate Treatment-Emergent Adverse Events • Most common: diarrhea (26.7%), though diarrhea is the primary symptom assoc
Slide 34: irEC is a disease of the mucosal epithelial barrier-immune interface
irEC is a disease of the mucosal epithelial barrier-immune interface Activation and amplification of T cells and macrophages by ICI – intended to kill tumor cells – have off-target effects causing injury to the gastrointestinal mucosal epithelial barrier and severe inflammation Gastrointestinal Muco
Slide 35: Pharmacology: Biomarkers support SER-155 repaired mucosal epithelial barrier
Pharmacology: Biomarkers support SER-155 repaired mucosal epithelial barrier & reduced GI inflammation consistent with drug’s design & clinical results Pharmacokinetics SER-155 strains colonized participants' GI tracts, i.e., engrafted, with the majority of strains observed across the study particip
Slide 36: SER-603
SER-603 36 Seres Therapeutics, Inc. © 2026
Slide 37: SER-603 IBD: Improve response & durability to IBD drugs
SER-603 IBD: Improve response & durability to inflammatory bowel disease (IBD) drugs Target Product Profile: Combination therapy in IBD Value Proposition Mechanism of Action Efficacy (TPP) • Target inflammatory microbes in gastrointestinal tract and compromised mucosal epithelial barrier • Biomarker
Slide 38: Key challenges in IBD suggest new therapeutic solutions are needed
Key challenges in IBD suggest new therapeutic solutions are needed 50% • Efficacy ceiling experienced by many patients due to non- 45% response or poor durability of response UC 40% Crohn’s • Safety concerns limit the potential for combining advanced Placebo 35% 7% therapies that are immunosuppressi
Slide 39: Monotherapy Proof of Concept: SER-603 in preclinical IBD models
Monotherapy Proof of Concept: SER-603 addresses microbiome-driven inflammation in preclinical disease models of IBD Biomarker (+) SER-603: LBP GF IL10-/- Evaluate treatment effect of SER-603 to microbiome designed to treat IBD mice address inflammatory microbiome test article ~4-5 weeks of colonizat
Slide 40: Combination Therapy Proof of Concept: SER-603 with anti-TNFα
Combination Therapy Proof of Concept: SER-603 increases the efficacy of anti-TNF𝛂 therapy in a preclinical model of microbiome-driven inflammation Evaluate treatment effect of SER-603 Biomarker (+) SER-603 & GF IL10-/- in combination with anti-TNF𝛂 to microbiome mice Anti-TNF𝛂 address disease…
Slide 41: Biomarker Validation: bacterial features predict response to therapy
Biomarker Validation: Identified bacterial features can predict response to therapy in clinical datasets Selection of Biomarker (-) patients increases Wang et. al. 2025 - significant impact of microbiome remission after ustekinumab ~70% of patients on ustekinumab efficacy Biomarker (-) Non-inflammat
Slide 42: SER-147
SER-147 42 Seres Therapeutics, Inc. © 2026
Slide 43: SER-147 Cirrhosis Infection: reduce spontaneous bacterial peritonitis
Master SER-147 Cirrhosis Infection: Protect epithelial barrier integrity and clinically reduce spontaneous bacterial peritonitis in liver disease Value Proposition Target Product Profile: Preventing Infections in Chronic Liver Disease patients Leverage clinically proven mechanism with Mechanism of A
Slide 44: Key Data: Preclinical reduction in SBP bacteria and epithelial barrier protection
Key Data: Preclinical demonstration of reduction in SBP bacteria and protection of epithelial barrier Reduces abundance of pathogens causing most Significant protection of epithelial barrier integrity common infections in cirrhosis patients against inflammatory-cytokine driven damage Declining E. co
Slide 45: Path Forward
Path Forward 45 Seres Therapeutics, Inc. © 2026
Slide 46: Summary and path forward
Summary and path forward • Focusing on pipeline (1) targeting inflammatory and immune diseases and (2) keeping patients on their cancer therapy when they face potentially significant side effects such as irEC and BSIs. Pipeline of novel live biotherapeutics in areas • Considering next phase of devel
Slide 47: Appendix: SER-155 allo-HCT Phase 1b Study Results
Appendix --- SER-155 allo-HCT Phase 1b Study Results 47 Seres Therapeutics, Inc. © 2026
Slide 48: SER-155 Phase 1b study design in adult allo-HCT recipients
SER-155 Phase 1b study evaluated safety, pharmacology, and efficacy in adult allo- HCT recipients COHORT 1 COHORT 2 Open-label (n=15 enrolled) Placebo-controlled 1:1 (n=45 enrolled) SER-155 SER-155 Placebo results reported May 2023 results announced Sept. 2024 Primary Endpoints: Key Secondary Endpoi
Slide 49: SER-155 Safety: generally well tolerated with no treatment-related SAEs
SER-155 Safety: SER-155 was generally well tolerated with no treatment-related SAEs • All but one subject in the placebo arm experienced at least 1 TEAE • Most common for SER-155 treated subjects (≥50% and with Δ ≥5% greater than placebo): Treatment-emergent diarrhea (86% vs. 74% placebo), nausea (6
Slide 50: SER-155 Efficacy: 77% relative risk reduction in bacterial BSIs
SER-155 Efficacy: SER-155 associated with 77% relative risk reduction in bacterial BSIs and reduction in systemic antibiotic exposure Significant decrease in bacterial bloodstream infections in SER-155-treated subjects vs. Bloodstream infections placebo with 77% relative risk reduction Significantly
Slide 51: Bloodstream infections from HCT Day 0 to Day 100
Bloodstream infections from HCT Day 0 to Day 100: Lower incidence in SER-155 treated subjects vs. placebo Bloodstream infections from Day 0 SER-155 Placebo to Day 100 n=20 n=14 (# patients) n (%) n (%) Subjects with confirmed BSI 2 (10.0) 6 (42.9) 95% confidence interval (1.2, 31.7) (17.7, 71.1) mIT
Slide 52: Cumulative exposure to systemic antibacterials / antimycotics through Day 100
Cumulative exposure to systemic treatment antibacterials / antimycotics through HCT Day 100: Lower incidence in SER-155 treated subjects vs. placebo Cumulative Antibacterial or SER-155 Placebo Antimycotic Exposure n=20 n=14 (HCT Days) n (SD) n (SD) Mean (SD) 9.2 (5.44) 21.1 (20.31) Median 9.0 14.0 M
Slide 53: Cumulative exposure rate to systemic antibacterials / antimycotics through Day 100
Cumulative exposure rate to systemic treatment antibacterials / antimycotics through HCT Day 100: Lower incidence in SER-155 treated subjects vs. placebo Cumulative Antibacterial or SER-155 Placebo Antimycotic Exposure Rate n=20 n=14 Rate (SD) Rate (SD) Mean (SD) 0.090 (0.0530) 0.305 (0.2898) Median
Seres Therapeutics — Investor Presentation (July 2026) on 6ix