On January 8, 2026, Day One Biopharmaceuticals announced the formal completion of its acquisition of Mersana Therapeutics following the satisfaction of all tender offer conditions. The deal carried a total equity value of approximately $129 million at closing, with a total potential transaction value of up to $285 million including milestone-based payments.
Transaction Structure and Strategic Integration
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Financial Terms: Day One purchased all outstanding shares of Mersana at $25 per share in cash, plus one non-tradable contingent value right (CVR) per share. The CVR entitles shareholders to potential future payments of up to $30.25 in cash upon reaching specified milestones.
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ADC Pipeline Expansion: With this merger, Day One has integrated a second novel antibody-drug conjugate (ADC) into its clinical development pipeline.
Therapeutic Potential of Emi-Le The acquisition’s centerpiece is Emi-Le (emiltatug ledadotin), an advanced ADC directed against B7-H4. This target is highly relevant in various malignancies, specifically adenoid cystic carcinoma (ACC), a rare salivary gland cancer for which no approved therapies currently exist.
Day One’s leadership stated that the acquisition of Mersana is a strategic fit, allowing the company to expand into adult oncology while maintaining its focus on rare cancers. Moving forward, the company plans to leverage its expertise to rapidly develop Emi-Le and pursue registration to meet the needs of underserved patient communities.
Source: https://www.pharmaceutical-technology.com/news/day-one-mersana-therapeutics-acquisition/?cf-view