Seres Therapeutics, Inc. MCRB
Seres Therapeutics, Inc. (Nasdaq: MCRB) is an oncology drug developer. Its lead program, SER-155, is in Phase 2 for Prevention of bacterial bloodstream infections in allogeneic hematopoietic stem cell transplantation (allo-HCT). Its next catalyst on record is SER-155 (irEC prophylaxis study): Study design submission to FDA (Q1 2027).
Upcoming catalysts
No catalyst is dated to the next 30 days or to an FDA action date.
Next further out: SER-155 (irEC prophylaxis study) — Study design submission to FDA (Q1 2027). 1 catalyst on record beyond the next 30 days; subscribers see each with its filing sentence.
Pipeline
| Program | Indication | Modality | Stage |
|---|---|---|---|
| SER-155 | Prevention of bacterial bloodstream infections in allo-HCT | biologic-other | Phase 2 |
| SER-155 | Treatment/prevention of immune checkpoint inhibitor-related enterocolitis (irEC) | biologic-other | Phase 1 |
| SER-603 | Not specified | biologic-other | Pre-clinical |
| SER-428 | Prevention of bloodstream infections in ICU patients | biologic-other | Pre-clinical |
| SER-147 | Prevention of bacterial bloodstream and spontaneous bacterial peritonitis infections in chronic liver disease | biologic-other | Pre-clinical |
Recent results and decisions
- Jul 31, 2026positive Investigator-sponsored Phase 1b trial showed 80% immunosuppressive-free clinical response at Day 15 in moderate-to-severe irEC patients treated with SER-155.
12 of 15 (80%) of participants treated with SER-155 achieved an immunosuppressive-free clinical response at Day 15, the primary efficacy endpoint.
Filing - Jul 8, 2026positive Open-label IST: 12 of 15 patients (80%) achieved immunosuppressive-free clinical response at Day 15 (primary endpoint); 33% complete remission at Day 15; no drug-related serious adverse events.
Following SER-155 dosing, 12 of 15 participants (80%) achieved an immunosuppressive-free clinical response at Day 15, the primary endpoint
Filing - Nov 5, 2025positive New post-hoc analysis of the completed Phase 1b (IDWeek Oct 2025): multi-drug resistance was seen only in BSI bacteria from placebo-treated participants, two of whom had fatal BSI outcomes; prior Phase 1b showed 77% relative BSI risk reduction.
Resistance to multiple antibacterial agents was observed only in the BSI bacteria from placebo-treated participants, two of whom had fatal outcomes related to their BSIs.
Filing
For subscribers
- Cash runway against each catalyst, with the company's own runway statement
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The free Monday brief
Last week's readouts and FDA decisions and the dated catalysts in the week ahead, each with its filing sentence.