Merck Acquires Cidara Therapeutics for $9.2 Billion

RAHWAY, New Jersey — Merck & Co., Inc. announced on Friday it will acquire Cidara Therapeutics in a deal valued at nearly $9.2 billion, securing access to an experimental drug aimed at preventing influenza.

The agreement comes as Merck seeks to diversify its revenue streams beyond Keytruda, with patents for the blockbuster cancer drug expected to expire in the coming years. The pharmaceutical giant will pay $221.50 per share in cash for Cidara, which represents a 108.9% premium over Cidara’s last closing price, causing its shares to double to $216.05 in premarket trading.

Merck will utilize a subsidiary to purchase all outstanding shares of Cidara, with the transaction’s equity value estimated at $6.96 billion. Since 2021, Merck has enhanced its late-stage pipeline almost threefold by pursuing both in-house developments and acquisitions, including an $11.5 billion purchase of Acceleron, which provided the drug Winrevair for treating pulmonary arterial hypertension.

In July, Merck completed a $10 billion buyout of UK-based Verona Pharma, acquiring Ohtuvayre, a newly approved treatment for chronic obstructive pulmonary disease, commonly known as “smoker’s lung.” Cidara is currently working on its long-acting antiviral drug CD388, which has the potential for universal flu prevention through a single dose, targeting all flu strains.

“We are confident that CD388 has the potential to be another important driver of growth through the next decade,” said Merck CEO Robert Davis.

CD388 falls under a category of drug-Fc conjugates that connect a drug to a human antibody fragment. It is presently undergoing late-stage trials focused on adults and adolescents who face a higher risk of influenza complications. In a mid-stage trial with healthy, unvaccinated adults aged 18 to 64, a single dose of the antiviral provided up to 76% protection from symptomatic influenza over a 24-week period compared to placebo.

The acquisition is slated to close in the first quarter of 2026.