In a company statement, Merck Chairman and CEO Robert Davis said the deal will enable the company to augment its pharmaceuticals with CD388, a long-acting antiviral designed to prevent influenza in individuals at high risk of complications.
“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,” he said.
Designed to prevent both influenza A and B, CD388 is currently in a Phase 3 study among adults and adolescents who are at high risk of developing complications from the flu. Due to positive results in Phase 2 testing, the U.S. Food and Drug Administration (FDA) has already granted CD388 a “Breakthrough Therapy Designation.”
“This milestone represents a transformational moment for Cidara and for our mission to redefine influenza prevention,” Jeffrey Stein, president and CEO of Cidara, said in the announcement. “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.”
The initial study participants received doses in September, and enrollment is continuing at 150 sites across the United States and the United Kingdom. The study’s target enrollment is 6,000 participants. An interim analysis will be announced during the first quarter of 2026.
Dean Y. Li, president of Merck Research Laboratories, said the acquisition will expand and complement Merck’s respiratory portfolio.
“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,” he said.
Both Merck’s and Cidara’s boards of directors have approved the transaction, under which a Merck subsidiary will acquire all of the outstanding shares of Cidara at $221.50 per share in cash. A majority of Cidara’s stockholders must still approve the deal, and the closing will be subject to certain conditions. Once approved, the transaction is expected to close in the first quarter of 2026.
A copy of the agreement will be filed with the Securities and Exchange Commission (SEC) and will be publicly available. Both firms plan to file annual, quarter, and current reports with the SEC, which will also be available to the public.
Influenza is described as an acute respiratory infection that is caused primarily by influenza viruses A and B. It’s estimated that 1 billion people worldwide are infected with seasonal influenza each year. Of that number, 3 to 5 million develop severe cases of the flu. Complications include pneumonia, sepsis, myocarditis, encephalitis, and even death in the most severe cases.
Globally, influenza has claimed up to 650,00 lives each year, with up to 52,000 in the United States alone.
Merck is a 130-year-old biotechnology firm noted for its development of vaccines and medicines such as Keytruda for cancer treatment and Januvia for type 2 diabetes. In addition, it operates a significant animal health division.
Headquartered in San Diego, California, Cidara Therapeutics is a biotechnology firm specializing in developing targeted immunotherapies for serious diseases such as cancer and fungal infections.
