Merck Commits $9.2 Billion to Acquire Cidara Therapeutics

Merck & Co has agreed to acquire Cidara Therapeutics for approximately $9.2 billion, paying $221.50 per share in cash to acquire all outstanding Cidara stock. The deal secures for Merck access to Cidara’s lead candidate, CD388, a long-acting antiviral designed to prevent influenza A and B infections, particularly among individuals at elevated risk of complications. CD388 is currently undergoing Phase III trials after earlier data demonstrated promising protection, and it has been granted Breakthrough Therapy and Fast Track designations by the US regulator.

The acquisition fits with Merck’s broader strategy to offset the anticipated expiration of patent protection for its flagship cancer drug. With the closure of this deal, Merck bolsters its respiratory and infectious disease portfolio, adding a potentially first-in-class flu prevention treatment that could provide season-long protection with a single dose—offering advantages over conventional vaccines, especially for older adults and immunocompromised patients.

Under the agreement, merger completion is expected in the first quarter of 2026, subject to regulatory approvals and customary closing conditions. A subsidiary of Merck will initiate a tender offer for all outstanding Cidara shares. The all-cash nature of the transaction and the substantial premium over Cidara’s recent share price underscore Merck’s confidence in CD388’s long-term commercial prospect.