Sanofi SA (NASDAQ: SNY)  announced it has entered into a definitive agreement to acquire Dynavax Technologies (NASDAQ: DVAX) in an all-cash transaction valued at approximately $2.2 billion, strengthening Sanofi’s vaccines portfolio and expanding its adult immunization pipeline.

Under the terms of the agreement, Sanofi will pay $15.50 per share in cash, representing a 39% premium to Dynavax’s closing price on December 23, 2025, and a 46% premium to the company’s three-month volume-weighted average price. Sanofi said it expects the transaction to close in the first quarter of 2026, subject to customary regulatory approvals and closing conditions. Sanofi plans to fund the acquisition using available cash and stated that the transaction will not affect its 2026 financial outlook.

The acquisition adds two key vaccine assets to Sanofi’s growing vaccines business. Dynavax’s marketed product HEPLISAV-B, an adult hepatitis B vaccine, features a two-dose regimen administered over one month, offering a faster alternative to traditional three-dose schedules that span six months.Sanofi will also gain Dynavax’s experimental shingles vaccine candidate Z-1018, which is currently in Phase 1/2 clinical development. The program is expected to complement Sanofi’s existing immunology and vaccines pipeline as the company continues to invest in differentiated adult vaccines.

Following the announcement, Dynavax shares rose sharply in morning trading, reflecting investor response to the acquisition premium. Sanofi said the deal is expected to close in early 2026, pending regulatory review. Upon completion, Dynavax will become a wholly owned subsidiary of Sanofi.

About Sanofi

Sanofi SA (NASDAQ: SNY) is a global biopharmaceutical company focused on human health, with core strengths in vaccines, immunology, oncology, rare diseases, and general medicines. Headquartered in France, Sanofi operates in more than 100 countries and is committed to advancing scientific innovation to improve patient outcomes worldwide.

About Dynavax Technologies

Dynavax Technologies Corporation (NASDAQ: DVAX) is a U.S.-based biotechnology company focused on developing and commercializing innovative vaccines. Its portfolio includes HEPLISAV-B, an approved adult hepatitis B vaccine, as well as a pipeline of immunization programs designed to address unmet medical needs.