06:47 AM EST, 11/13/2025 (MT Newswires) -- Day One Biopharmaceuticals ( DAWN ) said Thursday it has agreed to acquire Mersana Therapeutics ( MRSN ) to expand its oncology portfolio.

Under the terms of the agreement, Day One said it will launch a tender offer to purchase all outstanding Mersana shares for $25 per share in cash at closing, plus a non-tradable contingent value right worth up to $30.25 per share tied to future clinical, regulatory, and commercial milestones - for a total potential consideration of $55.25 per share, valuing the deal at up to about $285 million.

The company said the contingent value right milestones include up to $6 per share based on future sales thresholds and up to $9 per share for US regulatory approval of Mersana's lead program, Emi-Le, for adenoid cystic carcinoma, an aggressive cancer with a well-defined patient population and high unmet need, most often arising from the salivary gland.

Day One said it plans to fund the acquisition, expected to close by the end of January 2026, with existing cash and expects to advance Emi-Le through potential approval without additional financing.

Shares of Mersana Therapeutics ( MRSN ) more than tripled in Thursday's premarket activity.