Merck (known as MSD outside of the United States and Canada) is set to finalise its purchase of Cidara Therapeutics, a move that adds a promising late-stage antiviral to its portfolio and strengthens its infectious disease pipeline. The deal values Cidara at approximately $9.2 billion in cash, with Merck agreeing to pay $221.50 per share to acquire all outstanding Cidara stock.

Approval from both company boards has already been secured, and the transaction is expected to close in the first quarter of 2026 after satisfying regulatory and customary closing conditions. Cidara’s lead asset, CD388, is a long-acting, strain-agnostic antiviral currently in Phase 3 development for the prevention of influenza in people at higher risk of complications. Supported by encouraging Phase 2b results and designated a Breakthrough Therapy by the US Food and Drug Administration, CD388 represents a potential new option in global flu prevention alongside existing vaccines and treatments.

Merck views the acquisition as an important step in its science-led strategy to diversify its pipeline and address significant unmet needs in respiratory and infectious diseases. The added resources and global reach of Merck are expected to accelerate the development and potential commercialisation of CD388 once the deal completes.