BY Richard Summerfield
Pharmaceutical company Merck & Co. has announced is agreement to acquire Cidara Therapeutics for $9.2bn, adding a late-stage antiviral designed to prevent influenza infection to its pipeline.
The deal will see Merck pay $221.50 per share in cash for the company, a premium of 108.9 percent from Cidara’s last closing price before the acquisition was announced. The deal, which has been approved by both Merck’s and Cidara’s boards, is expected to close in the first quarter of 2026.
In recent years, Merck has spent billions of dollars to gain rights to a new kind of preventive flu medicine, hoping that the treatment is poised to become a top seller in the years ahead. The acquisition of Cidara is further evidence of the company’s desire to expand its portfolio of treatments as it prepares for patent losses that are expected to erode its sales by $18bn over the next five years. In 2028, Merck faces patent expiration for Keytruda, the best-selling drug in pharmaceutical history, which accounted for almost half of the company’s revenue in 2024. In July, the company also announced a similar-sized purchase, when it agreed to buy respiratory drugmaker Verona Pharma Plc for around $10bn.
The deal for Cidara revolves around the company’s drug CD388, a long-acting treatment to prevent the flu in people who are at higher risk of complications. CD388 is currently in late-stage trials, with interim study results expected next year. It has also been granted a type of Food and Drug Administration designation that should speed up a future review. In recent research notes, RBC Capital Markets projected a $3.8bn market opportunity for CD388.
CD388 is an antiviral that combines a small molecule with a protein fragment. It is not a vaccine, meaning it does not depend on producing an immune response. Rather, it is a long-acting treatment to prevent the flu in people who are at higher risk of complications. Cidara says CD388 could provide an additional option to vaccines and antivirals to help prevent influenza.
“This acquisition expands and complements our respiratory portfolio and pipeline. Influenza continues to pose a significant global health threat, causing widespread illness, morbidity and death each year especially in older adults and immunocompromised individuals, such as those with cancer and chronic diseases,” said Dean Y. Li, president of Merck Research Laboratories. “CD388 is a novel late-phase candidate with important strain-agnostic properties being evaluated for the prevention of symptomatic influenza in high-risk individuals.”
“We continue to execute our science-led business development strategy, augmenting our pipeline with CD388, a potentially first-in-class, long-acting antiviral designed to prevent influenza in individuals at higher risk of complications,” said Robert M. Davis, chairman and chief executive of Merck. “We intend to build on the Cidara team’s remarkable progress and are confident that CD388 has the potential to be another important driver of growth through the next decade, creating real value for shareholders.”
News: Merck bets on flu prevention with $9.2 billion deal for Cidara Therapeutics