By Colin Kellaher
Day One Biopharmaceuticals has struck a deal to buy fellow biopharmaceutical company Mersana Therapeutics for up to $285 million in cash.
Day One on Thursday said it will pay an initial $25 a share, or $119 million, for Mersana, nearly triple Wednesday's closing price of $8.87 for the Cambridge, Mass., clinical-stage company.
Mersana shareholders will also receive contingent value rights worth up to an additional $30.25 a share, for a total potential deal consideration of $55.25 a share.
Shares of Mersana were recently up 215% at $27.95 in premarket trading.
Day One, based in Brisbane, Calif., said the acquisition of Mersana bolsters its portfolio with the antibody-drug conjugate emiltatug ledadotin, which has shown early anti-tumor activity in a Phase 1 study in adenoid cystic carcinoma type-1, a cancer with high unmet need and a lack of therapeutic options.
The contingent value rights in the deal are tied to development and sales milestones for emiltatug ledadotin.
Day One said it plans use cash on hand to finance the acquisition, which is slated to close by the end of January.
Write to Colin Kellaher at colin.kellaher@wsj.com
(END) Dow Jones Newswires
November 13, 2025 06:23 ET (11:23 GMT)
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