Merck has announced a major expansion of its infectious disease portfolio with a definitive agreement to acquire Cidara Therapeutics, Inc. for approximately $9.2 billion. The all-cash transaction, valued at $221.50 per share, brings Cidara’s late-stage antiviral candidate CD388 directly into Merck’s pipeline as the company seeks to diversify its portfolio with innovative, long-acting preventative treatments.
The acquisition represents a strategic move for Merck, aligning with its long-standing approach of targeting high-impact scientific assets backed by strong development data. CD388, Cidara’s lead candidate, is considered one of the most promising antiviral innovations currently in development. Designed as a long-acting, strain-agnostic agent, CD388 aims to prevent infection from both influenza A and B, a significant advantage over seasonal vaccines that must be reformulated each year to match circulating strains.
CD388 combines a small-molecule neuraminidase inhibitor with Cidara’s proprietary drug-Fc conjugate (DFC) platform. This design is intended to provide durable protection against symptomatic influenza, particularly in groups most vulnerable to severe complications, such as older adults, cancer patients, and individuals with compromised immune systems.
The therapy is currently in the Phase 3 ANCHOR trial, following strong Phase 2b data in the NAVIGATE study, which demonstrated its effectiveness in preventing symptomatic, laboratory-confirmed influenza among unvaccinated adults. The U.S. Food and Drug Administration has recognized its potential through both Fast Track and Breakthrough Therapy designations, signaling the agency’s acknowledgment of the urgent need for more effective flu-prevention options.
For Merck, adding CD388 to its pipeline complements its existing respiratory portfolio and fills a critical unmet need at a time when influenza continues to cause significant global health burdens. Seasonal influenza leads to millions of infections each year and disproportionately affects high-risk populations. As viral strains evolve and vaccine hesitancy persists, demand for alternative prevention strategies continues to grow.
Cidara leadership characterized the acquisition as a transformative milestone. The company has dedicated its efforts to advancing DFC therapeutics and redefining how influenza can be prevented beyond traditional vaccines. With Merck’s global scale, regulatory strength, and commercial infrastructure, CD388 is positioned to reach markets internationally once approved.
The transaction has been unanimously approved by the boards of both companies. It will be executed through a tender offer by a Merck subsidiary, followed by a merger to acquire all outstanding Cidara shares. Completion of the deal remains subject to customary closing conditions, including clearance under the Hart-Scott-Rodino Antitrust Improvements Act. Merck expects the acquisition to close in the first quarter of 2026, accounting for it as an asset acquisition on its financial statements.
With this deal, Merck reinforces its commitment to science-driven expansion and long-term growth, while Cidara gains the resources necessary to bring its innovative antiviral approach to patients worldwide. If successful, CD388 could become one of the most significant advancements in influenza prevention in more than a decade.