Merck agreed to acquire Cidara Therapeutics for $9.2 billion, paying $221.50 per share in cash to obtain CD388, a late‑stage, long‑acting antiviral designed to prevent seasonal influenza. Cidara’s CD388 showed up to ~76% protection at the highest dose in a mid‑stage study and has moved into Phase 3; the program also drew BARDA support intended to expand U.S. manufacturing. The deal follows interest and prior passthroughs of the asset after Johnson & Johnson’s Janssen wound down infectious disease R&D and highlights Big Pharma’s push to secure seasonal respiratory prophylactics ahead of vaccine uptake uncertainties.