Rahway, NJ & San Diego, CA | January 2026
Merck & Co., Inc. has confirmed that its approximately $9.2 billion acquisition of Cidara Therapeutics is expected to close in the first quarter of 2026, subject to customary regulatory approvals and closing conditions. The transaction represents one of the largest biopharma M&A deals announced in 2025 and signals Merck’s strategic push to strengthen its infectious disease and preventive medicine portfolio.
Under the terms of the agreement, Merck will acquire all outstanding shares of Cidara Therapeutics for $221.50 per share in cash, valuing the San Diego–based biotech at roughly $9.2 billion.
Strategic Rationale: Long-Acting Antiviral Prevention
The acquisition is anchored by CD388, Cidara’s lead investigational asset, a long-acting, strain-agnostic antiviral designed for influenza prevention. CD388 is currently in Phase 3 development and is intended to provide season-long protection against both influenza A and B through a single administration.
Unlike traditional antivirals and vaccines, CD388 leverages Cidara’s proprietary drug-Fc conjugate platform, combining a small-molecule antiviral with an antibody fragment to extend durability and dosing intervals. The program has received Breakthrough Therapy and Fast Track designations, underscoring its potential clinical and public health impact.
Pipeline Diversification Ahead of Patent Expiries
The Cidara acquisition aligns with Merck’s broader pipeline diversification strategy, as the company prepares for future revenue pressure from major patent expirations later in the decade. By adding a late-stage, prevention-focused asset, Merck strengthens its position in respiratory disease, a therapeutic area with persistent unmet need and global relevance.
Merck plans to apply its global development, regulatory, and commercial infrastructure to accelerate CD388’s path toward potential approval and commercialization.
Transaction Highlights
- Transaction Value: Approximately $9.2 billion
- Structure: All-cash acquisition
- Price per Share: $221.50
- Lead Asset: CD388 (Phase 3, long-acting influenza prevention)
- Expected Close: First quarter of 2026
The transaction has been approved by the boards of both companies and is subject to standard regulatory clearances and shareholder tender requirements.
Industry and Market Context
The deal reflects a broader trend in biopharma M&A, where large pharmaceutical companies are prioritizing late-stage, differentiated assets that address population-level health risks. Influenza prevention remains a critical focus area, particularly for elderly and high-risk populations, where current options leave meaningful gaps.
Merck’s move positions it to compete beyond vaccines alone, potentially redefining how seasonal and pandemic-preparedness strategies are deployed.
Outlook
If completed as expected in early 2026, Merck’s acquisition of Cidara Therapeutics could establish CD388 as a new category of long-acting antiviral prevention, complementing vaccines and reshaping respiratory disease management. Investors and industry observers will closely track late-stage clinical outcomes and regulatory milestones as Merck integrates the program into its pipeline.
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