Following a feud with activist investor Deep Track Capital in the first half of 2025, vaccine developer Dynavax Technologies has rounded out the year by agreeing to sell itself to France’s Sanofi.
To get its hands on the Emeryville, California-based company and its approved adult hepatitis B vaccine Heplisav-B, Sanofi will pay $15.50 per Dynavax share in cash, which works out to a total deal value of roughly $2.2 billion, the French pharma said in a Dec. 24 press release.
The acquisition, which is expected to close in 2026’s first quarter, also grants Sanofi access to Dynavax’s promising shingles prophylactic Z-1018, which is currently in phase 1/2 testing and could eventually challenge GSK’s incumbent shot Shingrix, if approved.
The addition of Dynavax’s hepatitis vaccine Heplisav-B is expected to help round out Sanofi’s armamentarium of approved adult immunizations, which has traditionally leaned heavily on the drugmaker’s roster of influenza shots. In 2025’s third quarter, Sanofi reported that its overall vaccine sales had slipped nearly 8% to 3.4 billion euros, which the company blamed in October on “lower influenza sales.”
Meanwhile, Sanofi already boasts a combination hepatitis B vaccine for young children in Vaxelis, which also protects against conditions like tetanus, pertussis and diphtheria.
Given that Heplisav-B is indicated for adults, Dynavax’s commercial vaccine won’t be affected by the recent vote from the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices to remove a recommendation for universal hepatitis B vaccination for infants at birth in the U.S.
The buyout comes amid broader shifts in vaccination trends and policy in the U.S., especially for children, under a Department of Health and Human Services led by noted vaccine skeptic Robert F. Kennedy Jr.
Dynavax’s adult hepatitis vaccine Heplisav-B, approved by the FDA in 2017, sets itself apart from other shots in the indication thanks to its two-dose regimen administered over just one month, Sanofi noted in its release. By comparison, other hepatitis B vaccines must be given in three doses over six months.
For all of 2024, Dynavax recorded Heplisav-B sales of $268 million, which represented a 26% jump over the sum the vaccine generated the year before.
Meanwhile, the company’s experimental shingles vaccine Z-1018 displayed promising signals over the summer in the first part of a phase 1/2 study, which looked at various formulations and dosing regimens of the recombinant subunit shot in healthy adults between the ages of 50 and 69 years.
In the trial, which measured Z-1018 against GSK’s Shingrix, the formulation Dynavax has decided to go forward with in the second part of the study helped trigger a 100% humoral vaccine response rate—a measure of antibody production—at one month following a second dose, compared to 96.9% in the study’s Shingrix cohort.
In terms of responses for gE-specific CD4+ T cells, the study’s Z-1018 group showed a cellular immune response rate of 89.7% versus 93.5% for the Shingrix arm, Dynavax said in August.
“Joining Sanofi will provide the global scale and expertise needed to maximize the impact of our vaccine portfolio,” Ryan Spencer, Dynavax’s chief executive, said in a statement.
“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,” he continued.
Dynavax has accepted Sanofi’s offer in the wake of a contentious battle with activist investor Deep Track earlier in 2025.
Back in February, Deep Track intensified demands for Dynavax to refocus its efforts on its lone approved product, Heplisav, and forego what the investor called a “misguided empire-building exercise” of pursuing external asset acquisitions.
At the time, Deep Track estimated that the nearly eight-year-old vaccine Heplisav could generate more than $1 billion through 2030. A key part of Deep Track’s plan was to instill four of its own picks to Dynavax’s board.
But Dynavax held its ground and ultimately prevailed at its annual meeting in June, reelecting all four of its own candidates and defeating Deep Track’s attempts to unseat the directors, Reuters reported over the summer.
Sanofi’s decision to snap up Dynavax follows a number of other high-profile acquisitions by the French Big Pharma in 2025.
In a massive deal worth up to $9.5 billion, Sanofi in June agreed to purchase Blueprint Medicines, gaining access to the company’s portfolio of rare immunological disease treatments, including the systemic mastocytosis pill Ayvakit. Blueprint in 2024 estimated that Ayvakit could generate $2 billion in peak sales.
Meanwhile, Sanofi in July laid out $1.15 billion upfront for Vicebio, securing preclinical and phase 1 vaccine candidates to grow its pipeline for respiratory syncytial virus (RSV) beyond mRNA.
Vicebio’s most advanced candidate comes in the form of VXB-241, a bivalent vaccine prospect taking aim at RSV and human metapneumovirus.