On November 14, 2025 Merck (NYSE: MRK), known as MSD outside of the United States and Canada, and Cidara Therapeutics, Inc. (Nasdaq: CDTX) ("Cidara"), a biotechnology company developing drug-Fc conjugate (DFC) therapeutics, reported that the companies have entered into a definitive agreement under which Merck, through a subsidiary, will acquire Cidara for $221.50 per share in cash, for a total transaction value of approximately $9.2 billion.
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"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 officer, 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."
Cidara’s lead candidate, CD388, consists of a small molecule neuraminidase inhibitor stably conjugated to a proprietary Fc fragment of a human antibody designed to prevent influenza A and B. CD388 is currently being evaluated in the Phase 3 ANCHOR study (NCT07159763) among adult and adolescent participants who are at higher risk of developing complications from influenza. Supported by results from the Phase 2b NAVIGATE study (NCT06609460), the U.S. Food and Drug Administration (FDA) granted CD388 Breakthrough Therapy Designation. The NAVIGATE study met all primary and secondary endpoints associated with preventing symptomatic laboratory-confirmed influenza in healthy unvaccinated adults ages 18 to 64. CD388 was previously granted Fast Track Designation by the FDA.
"This milestone represents a transformational moment for Cidara and for our mission to redefine influenza prevention," said Jeffrey Stein, Ph.D., president and chief executive officer of Cidara. "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. "CD388 is a novel late-phase candidate with important strain agnostic properties being evaluated for the prevention of symptomatic influenza in high-risk individuals."
The transaction has been approved by both Merck’s and Cidara Therapeutics’ Boards of Directors. Under the terms of the merger agreement, Merck, through a subsidiary, will acquire all of the outstanding shares of Cidara Therapeutics. The acquisition is subject to a majority of Cidara Therapeutics’ stockholders tendering their shares in a tender offer that will be initiated by a subsidiary of Merck. The closing of the proposed transaction will be subject to certain conditions, including the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions. The transaction is expected to close in the first quarter of 2026 and is expected to be accounted for as an asset acquisition.
A copy of the merger agreement pursuant to the transaction will be filed with the Securities and Exchange Commission ("SEC") and will be publicly available. In addition, Merck and Cidara will file annual, quarterly and current reports and other information with the SEC, which are available to the public from commercial document-retrieval services and at the SEC’s website at www.sec.gov. Copies of the documents filed with the SEC by Merck may be obtained at no charge on Merck’s internet website at www.merck.com or by contacting Merck at 126 East Lincoln Avenue P.O. Box 2000, Rahway, NJ 07065 USA, or by phone at (908) 740-4000. Copies of the documents filed with the SEC by Cidara Therapeutics may be obtained at no charge from Cidara Therapeutics’ internet website at www.cidara.com or by contacting Cidara at 6310 Nancy Ridge Dr #101, San Diego, CA 92121 or by phone at (858) 283-8821.
Investor Call
Merck will hold an investor call Monday, November 17, 2025 at 8 a.m. ET to discuss the proposed transaction. Journalists who wish to ask questions are requested to contact a member of Merck’s Media Relations team at the conclusion of the call. Investors, journalists and the general public may access a live audio webcast of the call via this weblink. Additional details to join the call via dial in will be provided at a later time.
About Influenza
Influenza is an acute respiratory infection caused predominantly by influenza viruses A and B. An estimated 1 billion people worldwide are infected by seasonal influenza each year. Of the 1 billion, 3-5 million have severe cases of flu. Complications include pneumonia, exacerbation of chronic conditions, sepsis, myocarditis, encephalitis, and death in the most severe cases. Globally, an estimated 290,000-650,000 deaths occur due to flu each year with 6,300-52,000 deaths in the US.
About CD388
CD388 is an investigational drug-Fc conjugate (DFC) comprised of multiple copies of a potent small molecule neuraminidase inhibitor stably conjugated to a proprietary Fc fragment of a human antibody. DFCs are not vaccines or monoclonal antibodies but are low molecular weight biologics which are designed to function as long-acting small molecule inhibitors. CD388 was designed to prevent influenza infection in individuals at higher risk of influenza complications with the potential to provide season-long protection. CD388 is not a vaccine, therefore its activity is not dependent on an immune response and is expected to be efficacious in individuals regardless of immune status.
The ANCHOR study
The ANCHOR study (NCT07159763) is a Phase 3 randomized, double-blind, placebo-controlled study to evaluate the safety and efficacy of CD388, a novel long-acting antiviral conjugate, for the prevention of influenza in adults and adolescents at higher risk of developing influenza complication. The first participants were dosed in September 2025 and enrollment is ongoing in 150 sites in the Northern Hemisphere across the U.S. and the United Kingdom. The study has a target enrollment of 6,000 participants. The study will include an interim analysis in the first quarter of 2026 to assess the trial size and powering assumptions and to determine the potential need for additional enrollment.
(Press release, Cidara Therapeutics, NOV 14, 2025, View Source [SID1234659965])