Seres Therapeutics, Inc. MCRB
Seres Therapeutics, Inc. (Nasdaq: MCRB) is an infectious disease drug developer. Its lead program, SER-155, is in Phase 1 for Bloodstream infection prevention in allo-HCT patients; immune checkpoint-related enterocolitis (irEC). Its next catalyst on record is SER-428: IND-readiness (2026).
Upcoming catalysts
No catalyst is dated to the next 30 days or to an FDA action date.
Next further out: SER-428 — IND-readiness (2026). 1 catalyst on record beyond the next 30 days; subscribers see each with its filing sentence.
Pipeline
| Program | Indication | Modality | Stage |
|---|---|---|---|
| SER-155 (allo-HCT, Phase 1b completed; Phase 2 startup paused pending funding) | Bacterial bloodstream infections in allo-HCT | biologic-other | Phase 1 |
| SER-155 (investigator-sponsored Phase 1b, MSK) | Grade 2-3 immune checkpoint-related enterocolitis (irEC) | biologic-other | Phase 1 |
| SER-428 | Bloodstream infection prevention in ICU patients (liquid formulation) | biologic-other | Pre-clinical |
| SER-603 | Inflammatory bowel disease (UC, Crohn's) | biologic-other | Pre-clinical |
| SER-147 | Infection prevention in cirrhosis (SBP, BSI) | biologic-other | Pre-clinical |
Recent results and decisions
- 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
- Track record: every Phase 3 readout, FDA decision and guidance slip since 2014
- Expected move for each dated catalyst, from comparable past events
- Phase 2 evidence behind each Phase 3 readout
- Companies on the same target or class
- Full catalyst list with filing sentences, deals, registered trials, Excel export
Other phase 1 infectious disease companies
The free Monday brief
Last week's readouts and FDA decisions and the dated catalysts in the week ahead, each with its filing sentence.