MSD (the tradename of Merck & Co., Inc., Rahway, N.J., USA) has announced a definitive agreement to acquire Cidara Therapeutics, Inc., a biotechnology company developing drug-Fc conjugate (DFC) therapeutics. The deal, valued at approximately $9.2 billion, will see MSD purchase all outstanding Cidara shares at $221.50 per share in cash through a subsidiary.
The acquisition aligns with MSD’s strategy to strengthen its pipeline with scientifically advanced assets, particularly in infectious diseases. A central focus of the transaction is CD388, Cidara’s lead investigational candidate. CD388 is a potentially first-in-class, long-acting antiviral designed to prevent influenza A and B in individuals at elevated risk of complications. MSD expects the addition of CD388 to enhance its long-term growth prospects and broaden its respiratory health portfolio.
CD388 is built on Cidara’s proprietary drug-Fc conjugate platform, combining a small-molecule neuraminidase inhibitor with a human antibody Fc fragment to provide durable protection against influenza. The candidate is currently being evaluated in the global Phase 3 ANCHOR trial among adult and adolescent participants who face a higher likelihood of developing severe influenza-related complications.
The U.S. FDA has granted CD388 Breakthrough Therapy Designation, supported by promising data from the Phase 2b NAVIGATE study, which met all primary and secondary endpoints in preventing symptomatic, laboratory-confirmed influenza among healthy, unvaccinated adults aged 18–64. The candidate also previously received Fast Track Designation, underscoring its clinical potential.
For Cidara, the acquisition marks a significant milestone and an opportunity to accelerate the development and global reach of CD388. The company’s progress in advancing an alternative approach to influenza prevention has highlighted the unmet need for options beyond traditional vaccines and antivirals, particularly for high-risk populations.
MSD stated that the acquisition strengthens its respiratory illness pipeline at a time when influenza continues to cause substantial global morbidity and mortality. Older adults, immunocompromised individuals, and those with chronic conditions remain among the most vulnerable.
The Boards of Directors of both companies have approved the transaction. The acquisition will proceed through a tender offer for Cidara’s outstanding shares and is subject to regulatory approvals, including clearance under the Hart-Scott-Rodino Antitrust Act. The deal is expected to close in the first quarter of 2026 and will be accounted for as an asset acquisition.
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