---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-298005"
form_type: "8-K"
ticker: "MCRB"
cik: "0001609809"
company_name: "Seres Therapeutics, Inc."
filed_at: "2026-07-08T12:00:09+00:00"
generated_at: "2026-07-08T12:05:19.784368+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.7
calibrated_materiality_score: 0.7
confidence: "high"
source: SEC EDGAR
---

# Seres reports 80% immunosuppressive-free clinical response for SER-155 in irEC trial

## Summary
- 12 of 15 patients (80%) achieved primary endpoint: ≥1-grade diarrhea improvement without immunosuppressives at Day 15.
- 5 of 15 (33%) achieved complete remission (Grade 0 diarrhea) at Day 15; 2 of 15 (13%) maintained at Day 43.
- SER-155 well tolerated; no drug-related serious adverse events or bloodstream infections through Day 43.
- Biomarkers (fecal calprotectin, albumin) showed statistically significant reductions at Day 43, indicating reduced GI inflammation.
- Company engaging with potential partners for SER-155 development in irEC and seeking funding for allo-HCT Phase 2.

## SEC filing metadata
- accession: 0001193125-26-298005
- form_type: 8-K
- ticker: MCRB
- cik: 0001609809
- company_name: Seres Therapeutics, Inc.
- filed_at: 2026-07-08T12:00:09+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.7
- calibrated_materiality_score: 0.7
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1609809/000119312526298005/0001193125-26-298005-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1609809/000119312526298005/d130829d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-298005
- JSON: https://secwatch.observer/filing/0001193125-26-298005.json
- Plain text: https://secwatch.observer/filing/0001193125-26-298005.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.