Merck has agreed to acquire Cidara Therapeutics for roughly $9.2 billion to secure CD388, a long‑acting antiviral designed to prevent seasonal and pandemic influenza. The deal centers on CD388, a neuraminidase inhibitor conjugated to an Fc fragment, which is being tested in the Phase III ANCHOR trial and received breakthrough and fast‑track designations. Cidara reported positive Phase IIb NAVIGATE results showing prevention efficacy ranging from 57.7% (low dose) to 76.1% (high dose) over 24–28 weeks. Merck frames the acquisition as a strategic hedge against upcoming revenue gaps and to bolster its infectious‑disease portfolio ahead of Keytruda patent cliffs. Investors reacted strongly: Cidara shares surged and Merck emphasizes integration of the Cidara team to drive CD388 through late‑stage development and commercialization. The transaction accelerates consolidation in antivirals and expands Merck’s season‑long prevention options beyond vaccines.