Merck agreed to acquire Cidara Therapeutics for $9.2 billion in cash, securing rights to CD388, a late‑stage long‑acting antiviral designed to prevent seasonal influenza. The deal values Cidara at a 109% premium to its prior close and transfers a program that showed roughly 75% prevention at the highest dose in mid‑stage testing into Merck’s pipeline. CD388 is a drug‑Fc conjugate intended to provide broad A/B strain protection through a full flu season and has secured an expedited FDA designation, with pivotal readouts expected next year. Merck framed the acquisition as a strategic revenue hedge as Keytruda faces looming patent cliffs and as the company accelerates inorganic growth to replenish its late‑stage portfolio. The transaction includes prioritized manufacturing support from BARDA in the U.S. for supply chain scale‑up; interim phase‑3 data could be a major commercial and public‑health inflection point given declining vaccine uptake and variable shot efficacy. Analysts estimate multi‑billion dollar market potential if CD388 delivers durable, season‑long protection.