Merck agreed to acquire Cidara Therapeutics for approximately $9.2 billion to add a late-stage, long-acting antiviral designed to prevent seasonal and pandemic influenza. The deal centers on Cidara’s CD388 program, a small-molecule neuraminidase inhibitor conjugated to an Fc fragment that showed strong prevention efficacy in Phase IIb NAVIGATE and is now in the Phase III ANCHOR trial (NCT07159763). The acquisition brings forward a candidate with fast-track and breakthrough designations and positions Merck to augment its infectious-disease portfolio ahead of anticipated revenue pressures from Keytruda patent expirations. Merck leadership framed the purchase as a growth driver over the next decade, while investors rewarded Cidara shares sharply on the takeover announcement. CD388 demonstrated prevention efficacy ranging from the mid-50s to mid-70s across dose groups in NAVIGATE, and the Phase III program will test the candidate in higher-risk adolescents and adults over the flu season. Merck said it will integrate Cidara’s team and data into its development pathway and pursue regulatory filings pending ANCHOR results.