Merck to Acquire Cidara Therapeutics for $9.2 Billion to Bolster Influenza Prevention Pipeline

Merck (known as MSD outside the U.S. and Canada) and Cidara Therapeutics, Inc., a biotechnology company specializing in Drug-Fc Conjugate (DFC) therapeutics, have announced a definitive agreement under which Merck will acquire Cidara.

Acquisition Details

Acquirer: Merck (through a subsidiary).
Target: Cidara Therapeutics, Inc.
Transaction Value: Approximately $9.2 billion in total.
Price Per Share: $221.50 per share in cash.
Expected Close: First quarter of 2026.
Conditions: Subject to the approval of a majority of Cidara’s stockholders (via a tender offer) and regulatory clearance, including the expiration of the waiting period under the Hart-Scott-Rodino Act.

Strategic Asset: CD388

The primary driver for the acquisition is Cidara’s lead clinical candidate, CD388, a potentially first-in-class, long-acting antiviral drug designed for the prevention of influenza.

Mechanism: CD388 is a Drug-Fc Conjugate (DFC). It consists of a small molecule neuraminidase inhibitor (an antiviral component) stably conjugated to a proprietary Fc fragment of a human antibody. This DFC technology is designed to provide sustained activity.
Indication: Prevention of Influenza A and B in individuals at higher risk of complications.
Key Attributes: It is noted for its strain-agnostic properties, meaning it is expected to be effective against different circulating influenza strains.
Administration: Designed to be a long-acting antiviral.

Clinical Status and Designations

CD388 has demonstrated strong clinical progress, leading to key regulatory designations:

Clinical Milestone	Status	Details
Phase 3 Trial	Currently Enrolling	The ANCHOR study (NCT07159763) is evaluating CD388 among adults and adolescents at higher risk of complications from influenza.
Phase 2b Results	Successful	The NAVIGATE study (NCT06609460) met all primary and secondary endpoints in preventing symptomatic, laboratory-confirmed influenza in healthy, unvaccinated adults.
Regulatory Status	Designated	Granted Breakthrough Therapy Designation (FDA) and Fast Track Designation (FDA).

Leadership Commentary

Robert M. Davis, CEO, Merck: Stated the acquisition is a continuation of Merck’s science-led business development strategy. He expressed confidence that CD388 has the potential to be an “important driver of growth through the next decade.”
Jeffrey Stein, Ph.D., CEO, Cidara: Called the acquisition a “transformational moment” for Cidara, acknowledging that Merck’s global development and commercial capabilities provide the necessary expertise to bring this innovation to high-risk individuals.
Dr. Dean Y. Li, President, Merck Research Laboratories: Emphasized that the acquisition expands and complements Merck’s respiratory portfolio, addressing the significant global health threat posed by influenza, especially in older and immunocompromised individuals.

Merck views CD388 as a novel late-phase candidate that offers an additional prevention option alongside existing vaccines and traditional antivirals.