What Mersana Therapeutics does

Mersana Therapeutics was a clinical-stage biopharmaceutical company that developed antibody-drug conjugates (ADCs) for the treatment of cancer. Headquartered in Cambridge, Massachusetts and founded in 2001, the company operated a proprietary ADC platform with novel conjugation chemistry and linker technology, targeting two distinct biological pathways: B7-H4 (via Emi-Le / emiltatug ledadotin) and STING agonism (via XMT-2056). Its lead asset, Emi-Le, was a clinical-stage B7-H4-directed ADC in development for adenoid cystic carcinoma (ACC), a rare solid tumor with no FDA-approved therapies. XMT-2056, a STING-agonist ADC for HER2-positive cancers, was licensed to GSK in 2022 in a deal worth up to $1.36 billion in milestones but was later placed on FDA partial clinical hold and returned.

The company generated revenue exclusively through licensing agreements and milestone payments from pharmaceutical partners, as it had no commercialized products. The GSK partnership was the dominant commercial relationship and provided the principal validation of Mersana's platform, but that relationship was terminated by GSK in April 2026. Mersana's customer base was effectively limited to rare cancer patients enrolled in clinical trials, with no traditional distribution or product marketing infrastructure. The company had a headcount in the 101–250 range (firmographics), consistent with a clinical-stage biotech operating multiple IND-stage programs.

In January 2026, Mersana was acquired by Day One Biopharmaceuticals for $25 per share in cash plus contingent value rights worth up to $30.25 per share, with a total deal value of approximately $285 million. The company became a wholly owned subsidiary and was immediately delisted from Nasdaq. Day One was subsequently acquired by Servier in March 2026 to expand Servier's rare oncology portfolio, placing Emi-Le within a larger commercial-stage organization.

Name

Mersana Therapeutics

Legal name

Mersana Therapeutics, Inc.

Website

https://mersana.com

Company type

Private

Founded year

2017

Operating status

Acquired

Headcount range

101–250 employees

Short description

Mersana Therapeutics was a clinical-stage biopharmaceutical company developing antibody-drug conjugates (ADCs) for cancer, including Emi-Le for adenoid cystic carcinoma and XMT-2056 for HER2 cancers. Acquired by Day One Biopharmaceuticals in January 2026.

Ownership category

akta.pro rank

Product category

Oncology Biopharmaceuticals

NAICS

Pharmaceutical Preparation Manufacturing (325412), Biological Product (except Diagnostic) Manufacturing (325414)

SIC

Pharmaceutical Preparations (2834), Biological Products, (No Disgnostic Substances) (2836)

akta.pro primary industry

Antibody-Drug Conjugates (ADCs) & Antibody Conjugates (HLAAAAAE)

Keywords

• Antibody-drug conjugates
• Oncology therapeutics
• Targeted cancer therapy
• Biopharmaceutical development
• ADC platform

Headquarters

HQ city

Cambridge

HQ country

United States

HQ region

North America

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Technology or R&D, Personnel, Operations, Others

Revenue model

1. Licensing and milestone payments: Mersana generated revenue through licensing agreements with pharmaceutical partners, receiving milestone payments upon achievement of clinical and regulatory milestones. GSK partnership provided $100 million option payment; milestone payments from GSK were mentioned in Q3 2025 results.

Core offering

Mersana Therapeutics developed clinical-stage antibody-drug conjugates (ADCs) for the treatment of cancer. Its lead candidate, Emi-Le (emiltatug ledadotin), was a B7-H4-directed ADC in development for adenoid cystic carcinoma, a rare cancer with no approved therapies. The company also developed XMT-2056, a STING agonist ADC licensed to GSK. Revenue was generated through licensing and milestone payments from pharmaceutical partners.

Product overview

Mersana Therapeutics was a clinical-stage biopharmaceutical company focused on developing antibody-drug conjugates (ADCs) for cancer treatment. The company's primary product was Emi-Le (emiltatug ledadotin), a B7-H4-directed ADC being developed for adenoid cystic carcinoma. Mersana also developed XMT-2056, a STING agonist ADC that was licensed to GSK. The company operated its proprietary ADC platform technology and was acquired by Day One Biopharmaceuticals in January 2026 for approximately $285 million.

Differentiator

Problem solved

Functional benefit

Brands

• Emi-Le (emiltatug ledadotin): Antibody drug conjugate targeting B7-H4 for treating adenoid cystic carcinoma

Products and services

• Emi-Le (emiltatug ledadotin) A clinical-stage antibody-drug conjugate (ADC) targeting B7-H4 for the treatment of adenoid cystic carcinoma (ACC), a rare cancer with no approved therapies. Developed by Mersana Therapeutics and now advanced by Day One Biopharmaceuticals following its January 2026 acquisition of Mersana.
• XMT-2056 A STING agonist antibody-drug conjugate (ADC) for HER2-positive cancers, originally licensed to GSK. Development was discontinued in April 2026 after GSK terminated the partnership following an FDA partial clinical hold related to serious bleeding events.

Quantifiable outcome

• 60.57% share tender acceptance in acquisition

Segments2 records

Ideal customer profiles1 record

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature2 records

Partnerships

Two partnerships are on record, tiered major (terminated) and core (acquisition completed).

• GSKmajor (terminated)Strategic or Co-development Partner · 29 April 2026GSK partnered with Mersana on XMT-2056, a STING-agonist ADC for HER-2 cancers. GSK terminated the partnership in April 2026, walking away from a $100 million option deal. The drug had been placed on FDA partial clinical hold due to serious bleeding events including five deaths. GSK had originally acquired the program in 2022 in a deal worth up to $1.36 billion in milestones.
• Day One Biopharmaceuticalscore (acquisition completed)Strategic or Co-development Partner · 6 January 2026Day One Biopharmaceuticals acquired Mersana Therapeutics in January 2026 for $25 per share in cash plus contingent value rights worth up to $30.25 per share. The acquisition added Emi-Le (B7-H4-directed ADC) to Day One's pipeline for treating adenoid cystic carcinoma. Mersana became a wholly owned subsidiary with immediate delisting from Nasdaq.

Scale indicators4 records

Recent moves7 records

Expansion highlights3 records

Broad incumbents

• ImmunoGen (AbbVie): ADC pioneer whose Elaherte (mirvetuximab) was acquired by AbbVie for $10.1B in 2024. Directly comparable to Mersana as a clinical-to-commercial ADC specialist targeting oncology indications.
• Seagen (Pfizer): Leading ADC company with approved products (Adcetris, Padcev, Tukysa) acquired by Pfizer for $43B. Directly comparable ADC platform company with both early-stage assets and commercialized products.
• Daiichi Sankyo: Co-developer of Enhertu (with AstraZeneca), a blockbuster HER2 ADC. Comparable as a major ADC innovator and commercializer with deep pipeline in antibody-drug conjugates across multiple targets.
• Day One Biopharmaceuticals: Acquirer of Mersana and operator of Emi-Le post-2026; commercial-stage rare oncology company with FDA-approved OJEMDA. Comparable as a rare pediatric oncology-focused biopharma now integrating Mersana's ADC asset.
• AstraZeneca: Major ADC player through Enhertu (with Daiichi Sankyo) and Datroway. Comparable as a large pharma with significant ADC franchise investments, demonstrating the strategic value of ADC assets Mersana-style companies can attract.
• Gilead Sciences: Owns Trodelvy, a TROP2-directed ADC acquired through the Immunomedics deal. Comparable as a major biopharma with commercialized ADC assets and ongoing investments in antibody-drug conjugate development.

Direct peers

• Bolt Biotherapeutics: Clinical-stage ADC/ISAC developer with proprietary platform technology. Comparable as a small-cap, clinical-stage ADC company developing next-generation antibody conjugates for oncology indications.
• ProfoundBio: Clinical-stage ADC company developing novel antibody-drug conjugates for solid tumors. Directly comparable as a clinical-stage ADC specialist targeting oncology with proprietary platform technology.
• Pyxis Oncology: Clinical-stage oncology company developing ADC and immuno-oncology therapeutics. Comparable as a clinical-stage biopharma focused on ADC development for cancer treatment.

Emerging players

• Mablink Bioscience: Emerging ADC developer focused on next-generation antibody-drug conjugates with novel payload and linker technologies. Comparable as an emerging European-headquartered ADC platform company in clinical-stage development.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat3 records

Key risks6 records

Key highlights5 records

Customer concentration

• Xx.com/mersanaadc
• LinkedInlinkedin.com/company/mersana-therapeutics

Revenue estimate

Valuation estimate

Number of profiles

Profiles6 records

Funding overview

Funding rounds12 records

Investors20 records

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M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Mersana Therapeutics