Sanofi has agreed to acquire Dynavax Technologies in an all-cash transaction that would add the U.S.-marketed adult hepatitis B vaccine HEPLISAV-B and a Phase 1/2 shingles vaccine candidate to Sanofi’s vaccines portfolio.
Under the terms of the merger agreement, Sanofi plans to launch a cash tender offer to purchase all outstanding Dynavax shares for $15.50 per share, valuing the equity at approximately $2.2 billion. Dynavax said the offer represents a roughly 39% premium to its closing share price on December 23, 2025, and about a 46% premium to its three-month volume-weighted average price as of that date.
Dynavax’s flagship product, HEPLISAV-B, is marketed in the U.S. for adult hepatitis B immunization and is differentiated by a two-dose regimen administered over one month, compared with other hepatitis B vaccines commonly given in three doses over six months. The acquisition also includes Dynavax’s shingles candidate, Z-1018, currently in Phase 1/2 clinical development, along with additional vaccine pipeline programs.
Sanofi said the transaction would expand its presence in adult immunization by pairing Dynavax’s assets with Sanofi’s global development and commercial capabilities. Dynavax, for its part, highlighted the opportunity to scale HEPLISAV-B and advance its pipeline through Sanofi’s reach and resources.
Dynavax cited significant unmet need and adult vaccination opportunity in hepatitis B and shingles. In the U.S., the company said nearly 100 million adults born before 1991 remain unvaccinated against hepatitis B, with chronic infection posing risks including liver damage, cirrhosis, and liver cancer. Dynavax also pointed to shingles’ high lifetime incidence—about one in three adults—along with the potential for complications such as long-term nerve pain and serious eye infections.
The Dynavax board unanimously approved the transaction. Closing is subject to customary conditions, including tender of at least a majority of outstanding shares, expiration or termination of the Hart-Scott-Rodino waiting period, and other regulatory filings and clearances. If the tender offer is completed, a Sanofi subsidiary would merge with Dynavax, and remaining non-tendered shares would be converted into the right to receive the same $15.50 per share in cash. Sanofi said it expects to fund the acquisition with available cash resources and anticipates closing in the first quarter of 2026.
Support: Centerview Partners and Goldman Sachs are serving as financial advisors to Dynavax, with Cooley acting as legal counsel.
KEY QUOTES:
“Dynavax enhances Sanofi’s adult immunization presence by adding differentiated vaccines that complement Sanofi’s expertise. Its marketed adult hepatitis B vaccine and shingles candidate bring new options to our portfolio and underscore our commitment to providing vaccine protection across the lifespan.”
Thomas Triomphe, Executive Vice President, Vaccines, Sanofi
“Joining Sanofi will provide the global scale and expertise needed to maximize the impact of our vaccine portfolio. We believe Sanofi’s commercial reach, development capabilities and commitment to evidence-based immunization will amplify the opportunity for HEPLISAV-B and our innovative pipeline to address important public health needs, further advancing our mission to help protect the world against infectious disease. We are confident that this transaction – and the compelling value it provides – is in the best interests of the company and its stockholders.”
Ryan Spencer, Chief Executive Officer, Dynavax
