---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-25-089189"
form_type: "8-K"
ticker: "MCRB"
cik: "0001609809"
company_name: "Seres Therapeutics, Inc."
filed_at: "2025-04-22T23:59:59+00:00"
generated_at: "2026-05-23T09:19:10.906431+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.65
calibrated_materiality_score: 0.65
confidence: "high"
source: SEC EDGAR
---

# Seres Therapeutics effects 1-for-20 reverse stock split, effective April 21, 2025

## Summary
- Reverse stock split at 1-for-20 ratio, effective 5:00 PM ET on April 21, 2025.
- Common stock begins split-adjusted trading on Nasdaq on April 22, 2025 under symbol MCRB.
- No fractional shares will be issued; holders receive cash in lieu of fractional shares.
- Authorized shares and par value per share remain unchanged.
- Stockholders approved split range of 1:5 to 1:50; Board fixed final ratio at 1:20.

## SEC filing metadata
- accession: 0001193125-25-089189
- form_type: 8-K
- ticker: MCRB
- cik: 0001609809
- company_name: Seres Therapeutics, Inc.
- filed_at: 2025-04-22T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.65
- calibrated_materiality_score: 0.65
- confidence: high
- sec_items: 5.03, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1609809/000119312525089189/0001193125-25-089189-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1609809/000119312525089189/d97309d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-25-089189
- JSON: https://secwatch.observer/filing/0001193125-25-089189.json
- Plain text: https://secwatch.observer/filing/0001193125-25-089189.txt

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