French pharmaceutical powerhouse Sanofi announced on December 24, 2025, that it has agreed to acquire U.S.-based biotech Dynavax Technologies Corporation for approximately $2.2 billion in cash. The deal, structured as a tender offer at $15.50 per share, represents a 39% premium over Dynavax’s closing price on December 23 and a 46% premium to its three-month volume-weighted average price.
Dynavax, headquartered in Emeryville, California, specializes in vaccine development, with its flagship product HEPLISAV-B—a two-dose adult hepatitis B vaccine approved in the U.S. and known for its adjuvant technology that enhances immune response. The acquisition also brings Dynavax’s differentiated shingles vaccine candidate, Z-1018, currently in Phase 1/2 clinical trials, along with other early-stage pipeline projects.
Sanofi, a global leader in vaccines with established products in influenza, meningitis, and pediatric immunizations, views the purchase as a strategic move to strengthen its presence in adult vaccination markets. Thomas Triomphe, Sanofi’s Executive Vice President for Vaccines, stated that the deal “enhances Sanofi’s adult immunization presence by adding differentiated vaccines that complement Sanofi’s expertise,” leveraging the company’s worldwide development, manufacturing, and commercial capabilities.
The transaction will be funded with Sanofi’s available cash and is not expected to impact its 2025 financial guidance. Subject to customary closing conditions, including regulatory approvals and tender of a majority of shares, the acquisition is slated for completion in the first quarter of 2026.
This move aligns with Sanofi’s ongoing strategy to expand its immunology and vaccine franchises through targeted acquisitions, amid growing demand for adult vaccines addressing public health needs like hepatitis B and shingles prevention. Dynavax shareholders stand to benefit from the substantial premium, marking a successful exit for the biotech focused on innovative adjuvant-based therapies.