# Mersana Therapeutics

Source: https://onco.cc/companies/mersana/  
OnCo record `mersana` (Company). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

ADC platform company betting on B7-H4: emiltatug ledadotin (Emi-Le) has Breakthrough designation in adenoid cystic carcinoma and activity in TNBC after TOP1 ADCs.

## Summary

Mersana Therapeutics, based in Cambridge, Massachusetts, and listed as MRSN, is an antibody-drug conjugate platform company betting on B7-H4, whose emiltatug ledadotin, or Emi-Le, holds Breakthrough designation in adenoid cystic carcinoma and shows activity in triple-negative breast cancer after topoisomerase 1 ADCs. Emi-Le, also XMT-1660, produced a 23 percent objective response rate in TNBC previously treated with topoisomerase 1 ADCs and confirmed responses in adenoid cystic carcinoma, earning Breakthrough designation in May 2026, and the company also pioneered STING-agonist ADCs such as XMT-2056. OnCo links it to TNBC, head and neck, ovarian and endometrial cancer, to ADC sequencing as a term, and to the bottleneck of acquired resistance. Whether a non-topoisomerase payload can rescue patients after TOP1 ADCs fail is the open question.

## Fields

- Kind: Company
- Last checked: 2026-09-04
- HQ: Cambridge, MA
- Type: biotech
- Website: https://www.mersana.com
- Ticker: MRSN

## Sources

- Breakthrough designation (OncLive): https://www.onclive.com/view/fda-grants-breakthrough-therapy-designation-to-emi-le-for-adenoid-cystic-carcinoma

## Connected records

- cancers: [Endometrial cancer](https://onco.cc/cancers/endometrial/), [Head and neck squamous cell carcinoma](https://onco.cc/cancers/head-and-neck/), [Ovarian cancer](https://onco.cc/cancers/ovarian/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- fronts: [Antibody-Drug Conjugates](https://onco.cc/fronts/adcs/)
- technologies: [Antibody-drug conjugate (ADC)](https://onco.cc/technologies/adc/), [Immune-stimulating antibody conjugate (ISAC)](https://onco.cc/technologies/immune-stimulating-adc/)
- drugs: [Upifitamab rilsodotin](https://onco.cc/drugs/upifitamab-rilsodotin/)
- terms: [ADC sequencing](https://onco.cc/terms/adc-sequencing/)
- bottlenecks: [Acquired resistance to every therapy](https://onco.cc/bottlenecks/b-resistance/)
- companies: [Bain Capital Life Sciences](https://onco.cc/companies/bain-capital-life-sciences/)
- trials: [First-in-Human Study of XMT-1536 in Cancers Likely to Express NaPi2b](https://onco.cc/trials/nct03319628/)

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