# EDGAR Filing Document

**Accession Number:** 0001442836
**File Stem:** 9999999995-26-000105
**Filing Date:** 2026-1
**Character Count:** 1411
**Document Hash:** 0c71951951174535e9f0bfc6368775b6
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**9999999995-26-000105.hdr.sgml**: 20260109

**ACCESSION NUMBER**: 9999999995-26-000105

**CONFORMED SUBMISSION TYPE**: EFFECT

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260108

**DATE AS OF CHANGE**: 20260109

**EFFECTIVENESS DATE**: 20260108

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Mersana Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001442836
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** EFFECT
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-271766
- **FILM NUMBER:** 26521225

**BUSINESS ADDRESS:**
- **STREET 1:** 840 MEMORIAL DRIVE
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139
- **BUSINESS PHONE:** 617-498-0020

**MAIL ADDRESS:**
- **STREET 1:** 840 MEMORIAL DRIVE
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MERSANA THERAPEUTICS INC
- **DATE OF NAME CHANGE:** 20080813

### UNITED STATES
### SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## Notice of Effectiveness

**Date:** January 8, 2026

**Accession Number:** 0001104659-26-001281

**Form Type:** POS AM

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**CIK:** 0001442836

**Company Name:** Mersana Therapeutics, Inc.

**File Number:** 333-271766