Merck agreed to acquire Cidara Therapeutics for $9.2 billion to add CD388, an investigational, long-acting, strain-agnostic antiviral designed to prevent symptomatic influenza in high-risk populations. CD388 combines a small-molecule neuraminidase inhibitor with an antibody Fc fragment to create extended protection and is in Phase III ANCHOR testing. Cidara’s CD388 previously met primary and secondary endpoints in Phase IIb NAVIGATE and has FDA Breakthrough Therapy and Fast Track designations. Merck framed the acquisition as complementing its respiratory portfolio and expanding prevention options for older adults and immunocompromised patients. The deal accelerates Merck’s push into long-acting antivirals and prophylactics, a strategic move given persistent seasonal influenza burden and pandemic preparedness concerns. The transaction underscores Big Pharma appetite for late‑stage antivirals with broad protective potential.