---
schema_version: "secwatch.filing_event.v1"
accession: "0001104659-25-070245"
form_type: "8-K"
ticker: null
cik: "0001442836"
company_name: "Mersana Therapeutics, Inc."
filed_at: "2025-07-24T23:59:59+00:00"
generated_at: "2026-05-18T02:11:01.437035+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.65
calibrated_materiality_score: 0.65
confidence: "high"
source: SEC EDGAR
---

# Mersana Therapeutics to effect 1-for-25 reverse stock split to regain Nasdaq compliance

## Summary
- Reverse stock split ratio set at 1-for-25; effective July 25, 2025 at 5:00 p.m. ET.
- No fractional shares issued; stockholders receive cash in lieu of fractional shares.
- Common stock begins trading on split-adjusted basis July 28, 2025 under ticker MRSN.
- Authorized shares unchanged; proportionate adjustments made to equity awards and plans.
- Split intended to bring company into compliance with Nasdaq minimum bid price requirement.

## SEC filing metadata
- accession: 0001104659-25-070245
- form_type: 8-K
- cik: 0001442836
- company_name: Mersana Therapeutics, Inc.
- filed_at: 2025-07-24T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.65
- calibrated_materiality_score: 0.65
- confidence: high
- sec_items: 3.03, 5.03, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1442836/000110465925070245/0001104659-25-070245-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1442836/000110465925070245/tm2521489d1_8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001104659-25-070245
- JSON: https://secwatch.observer/filing/0001104659-25-070245.json
- Plain text: https://secwatch.observer/filing/0001104659-25-070245.txt

## Key facts
- Governance Changes
  Mersana Therapeutics, Inc.: 1-for-25 reverse stock split effected via Certificate of Amendment to the Fifth Amended and Restated Certificate of Incorporation (effective 2025-07-25).
  - Change: charter amendment
  - Effective: 2025-07-25
  source text: On July 24, 2025, Mersana Therapeutics, Inc. (the “Company”) filed a Certificate of Amendment to the Company’s Fifth Amended and Restated Certificate of Incorporation, as amended, (the “Certificate of Amendment”) with the Secretary of State of the State of Delaware, which will effect, as of 5:00 p.m. Eastern Time, on July 25, 2025 (the “Effective Time”), a 1-for-25 reverse stock split (the “Reverse Stock Split”) of the issued and outstanding shares of the Company’s common stock, $0.0001 par value per share (the “Common Stock”).
  evidence_url: https://www.sec.gov/Archives/edgar/data/1442836/000110465925070245/0001104659-25-070245-index.htm

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