Mersana Therapeutics, Inc., a clinical-stage biopharmaceutical company, develops antibody-drug conjugates (ADC) for cancer patients with unmet needs. The company develops Emi-Le (XMT-1660), a B7-H4-targeting Dolasynthen ADC candidate, which is in Phase 1 clinical trial; and XMT-2056, an Immunosynthen ADC targeting a novel human epidermal growth factor receptor 2 that is in Phase 1 clinical trial. Its preclinical products portfolio includes XMT-2068 and XMT-2175. It has strategic research and development collaborations with Janssen Biotech, Inc., Ares Trading S.A., Merck KGaA, and Asana Biosciences, LLC for the development of ADC product candidates. The company was formerly known as Nanopharma Corp. and changed its name to Mersana Therapeutics, Inc. in November 2005. Mersana Therapeutics, Inc. was incorporated in 2001 and is headquartered in Cambridge, Massachusetts. As of January 6, 2026, Mersana Therapeutics, Inc. operates as a subsidiary of Day One Biopharmaceuticals, Inc.