Day One Completes Acquisition of Mersana Therapeutics

Core Insights - Day One Biopharmaceuticals has successfully acquired Mersana Therapeutics, enhancing its pipeline with the clinical-stage antibody drug conjugate (ADC) emiltatug ledadotin (Emi-Le) targeting adenoid cystic carcinoma (ACC) [1][2][3] Acquisition Details - The acquisition involved purchasing all outstanding shares of Mersana at a price of $25 per share in cash, plus a non-tradable contingent value right (CVR) per share, potentially totaling up to $55.25 per share [3] - The tender offer for Mersana expired on January 5, 2026, with 3,029,135 shares validly tendered, representing 60.57% of Mersana's outstanding shares [4] Strategic Fit and Pipeline Expansion - The acquisition aligns with Day One's mission to expand into adult oncology while focusing on rare cancers, with Emi-Le showing promising early clinical data [2] - Emi-Le is directed against B7-H4, a target in certain cancers, including ACC, which has a significant unmet medical need [2][7] Company Background - Day One Biopharmaceuticals is dedicated to developing targeted therapies for life-threatening diseases, particularly in pediatric cancer, and aims to redefine cancer drug development [6][8]