Merck & Co. has agreed to acquire Cidara Therapeutics, a San Diego, California-based clinical-stage bio/pharmaceutical company developing drug-Fc conjugate therapeutics, for $9.2 billion. 

Cidara is using its proprietary Cloudbreak platform to develop drug-Fc conjugates (DFCs) that couple targeted small molecules and peptides to a human antibody fragment (Fc). These single molecule cocktails can be designed to inhibit specific disease targets and to simultaneously engage the immune system, according to information from Cidara.  

Cidara’s lead candidate, CD388, in Phase III development, 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. It is being evaluated in adult and adolescent participants who are at higher risk of developing complications from influenza. The drug has received Breakthrough Therapy Designation and Fast Track Designation by the US Food and Drug Administration.  

The transaction has been approved by both Merck’s and Cidara’s Boards of Directors. Under the terms of the merger agreement, Merck, through a subsidiary, will acquire all of the outstanding shares of Cidara. The acquisition is subject to a majority of Cidara’s 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.  

Source: Merck & Co.