Merck & Co Inc (NYSE:MRK, ETR:6MK) announced it has agreed to acquire Cidara Therapeutics Inc (NASDAQ:CDTX) in a $9.2 billion cash deal, paying $221.50 per share, more than double Cidara’s stock price prior to the announcement.
Shares of Merck slipped 1.5% to about $92 on the news, while Cidara shares surged 105% to $217.
The acquisition centers on Cidara’s lead candidate, CD388, a long-acting antiviral designed to prevent influenza in individuals at higher risk of complications. CD388 is a strain-agnostic agent intended to provide broad protection against influenza through a single dose.
In mid-stage trials, the drug demonstrated approximately 76% efficacy in preventing flu symptoms over six months.
CD388 is currently being evaluated in the Phase 3 ANCHOR study, following Breakthrough Therapy Designation from the US Food and Drug Administration (FDA).
Merck said the acquisition aligns with its strategy to diversify its drug portfolio ahead of the expected loss of patent protection for its blockbuster cancer therapy, Keytruda, by 2028.
The deal follows Merck’s $10 billion acquisition of Verona Pharma in July 2025, reflecting the company’s broader effort to expand into respiratory and antiviral therapies.
“This acquisition expands and complements our respiratory portfolio and pipeline,” said Dr Dean Y Li, president of Merck Research Laboratories. “Influenza continues to pose a significant global health threat, particularly for older adults and immunocompromised individuals.”
Dr Jeffrey Stein, Cidara CEO, added: “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 transaction is expected to close in the first quarter of 2026, pending regulatory approvals.