Merck, known as MSD outside of the United States and Canada, and Cidara Therapeutics, a biotechnology company developing drug-Fc conjugate (DFC) therapeutics, announced a definitive merger agreement on November 14th, 2025. According to a company press release, Merck will pay $221.50 per share, or approximately $9.2 billion, in cash to acquire Cidara Therapeutics. The transaction is expected to close in Q1 2026.
Cidara’s lead candidate is CD388, an investigational DFC composed of multiple copies of a small molecule neuraminidase inhibitor stably conjugated to a proprietary Fc fragment of a human antibody. Cidara is investigating CD388 as a long-acting, strain-agnostic antiviral agent for the prevention of influenza in patients at higher risk of complications from the illness.
FDA granted CD388 a Fast Track Designation in June 2023. Additionally, following results from the Phase IIb NAVIGATE study, FDA granted the candidate a Breakthrough Therapy designation in October 2025. CD388 is currently being evaluated in the Phase III ANCHOR study, which began dosing study participants in September 2025. An interim analysis is expected in Q1 2026.
“This milestone represents a transformational moment for Cidara and for our mission to redefine influenza prevention,” said Jeffrey Stein, President, CEO, Cidara Therapeutics, in the release. “Thanks to the extraordinary dedication of our team, the Phase 2b NAVIGATE study delivered compelling results that demonstrate CD388’s potential to provide an additional option to vaccines and antivirals to help address unmet needs in influenza prevention. Merck’s global development, regulatory and commercial capabilities provide the expertise and resources needed to bring this important innovation to those individuals who need it most.”
“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 Dr. Dean Y. Li, President, Merck Research Laboratories, in the release. “CD388 is a novel late-phase candidate with important strain-agnostic properties being evaluated for the prevention of symptomatic influenza in high-risk individuals.”
