Merck agreed to buy Cidara Therapeutics for approximately $9.2 billion to add the long‑acting influenza prophylactic CD388 to its antiviral portfolio. Cidara’s CD388—a small‑molecule neuraminidase inhibitor conjugated to a human Fc fragment—is in a Phase III ANCHOR trial after positive Phase IIb NAVIGATE results that showed prevention efficacy (PE) of 57.7%–76.1% across dose groups. Merck said the acquisition will accelerate CD388’s development as an alternative or complement to seasonal vaccines; Cidara’s CEO Jeffrey Stein highlighted the Phase IIb topline data supporting prevention up to 28 weeks. Merck chairman and CEO Robert M. Davis framed the deal as a multi‑year growth driver for the company’s infectious‑disease pipeline. The transaction reconfigures the influenza prevention landscape by shifting a late‑stage antiviral into a major pharma balance sheet and could shape commercial and clinical strategies for high‑risk populations if Phase III confirms efficacy and safety.