On November 13, 2025 Day One Biopharmaceuticals, Inc. (Nasdaq: DAWN) ("Day One" or the "Company"), a biopharmaceutical company dedicated to developing and commercializing targeted therapies for people of all ages with life-threatening diseases, reported it has signed a definitive merger agreement for Day One to acquire Mersana Therapeutics, Inc. ("Mersana").
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The transaction positions the Company for continued success and expansion of its oncology portfolio, adding Emi-Le, a potential first-in-class monotherapy for patients with ACC, an aggressive cancer with a well-defined patient population and high unmet need, most often arising from the salivary gland. The early anti-tumor activity observed with Emi-Le in an ongoing Phase 1 study, in a disease with a clear unmet medical need, may support a fast path to registration. Emi-Le represents an innovative and differentiated ADC directed against B7-H4, a well-characterized target in certain cancers. B7-H4 is highly expressed in ACC as well as in other adult and pediatric cancers. As a novel targeted investigational agent with monotherapy anti-tumor activity intended for a well-defined patient population without any approved therapies or a clear standard of care, the Company believes that Emi-Le is well positioned for potential rapid development and commercialization.
"This acquisition will add a potential game-changing new medicine to the Day One portfolio and, if approved, will broaden our opportunities for patient impact and for continued growth and value creation," said Jeremy Bender, Ph.D., chief executive officer of Day One. "The addition of the Emi-Le program to our portfolio allows us to leverage the research and development expertise, and the commercial capabilities, that already exist within Day One to address underserved, rare and life-threatening cancers in patients of all ages."
Terms of the Agreement
Under the terms of the definitive merger agreement, Day One will promptly commence a tender offer to acquire all of the outstanding shares of Mersana common stock at a price of $25 per share in cash at closing plus one non-tradable CVR per share to receive certain potential milestone payments of up to an aggregate of $30.25 per CVR in cash, for total consideration of up to $55.25 per share in cash, representing a total equity value of approximately $129 million at closing and representing a total deal value of up to approximately $285 million. The CVR is payable subject to certain terms and conditions of achievement of the following milestones:
Clinical Milestones
· A development milestone related to an existing partnership agreement: $1.25 per share
· Breakthrough Therapy Designation for ACC granted by FDA: $1.00 per share
· First dosing of a participant in a registrational trial of Emi-Le for ACC-1: $4.00 per share
Regulatory/Sales Milestones
· Regulatory approval granted by FDA in Emi-Le for ACC-1: $9.00 per share
· First commercial sale of Emi-Le in a major EMA market: $2.00 per share
· First commercial sale of Emi-Le in Japan: $1.00 per share
· Annual net sales of Emi-Le exceed $100 million by 2032: $2.00 per share
· Annual net sales of Emi-Le exceed $200 million by 2035: $4.00 per share
· Annual net sales of Emi-Le exceed $300 million by 2037: $6.00 per share
Day One expects to finance the acquisition with existing cash resources. Day One’s strong cash position and financial profile is expected to enable development of Emi-Le through potential approval with no additional financing required.
The transaction is expected to close by the end of January 2026, subject to receipt of applicable regulatory approvals and the satisfaction of other customary conditions.
Advisors
Gordon Dyal & Co., LLC is acting as the exclusive financial advisor to Day One, with Fenwick & West LLP serving as legal counsel. TD Cowen is acting as financial advisor to Mersana, with Wilmer Cutler Pickering Hale and Dorr LLP serving as legal counsel.
Conference Call
Day One will host a conference call and webcast today, Nov. 13 at 8:00 am Eastern Time. To access the live conference call by phone, dial 877-704-4453 (domestic) or 201-389-0920 (international), and provide the access code 13757215. Live audio webcast will be accessible from the Events page. To ensure a timely connection to the webcast, it is recommended that participants register at least 15 minutes prior to the scheduled start time. An archived version of the webcast will be available for replay on the Events section of the Day One Media & Investors page for 30 days following the event.
(Press release, Day One, NOV 13, 2025, View Source [SID1234659896])