Sanofi has entered into an agreement to acquire Dynavax Technologies Corporation (Dynavax). The acquisition augments Sanofi’s presence in adult immunisation by bringing together Dynavax’s vaccines with Sanofi’s global scale, development capabilities and commercial reach.

Dynavax’s adult hepatitis B vaccine HEPLISAV-B is currently marketed in the US and is differentiated by its two-dose regimen over one month, which enables high levels of seroprotection faster than other hepatitis B vaccines, which are given in three doses over six months.

The acquisition also includes Dynavax’s shingles vaccine candidate (Z-1018), which is currently in phase I/II clinical development and additional vaccine pipeline projects.

“Dynavax enhances Sanofi’s adult immunisation 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,” said Thomas Triomphe, Executive Vice President, Vaccines, Sanofi.

Hepatitis B and shingles represent a public unmet health need and adult vaccination opportunities. In the US alone, nearly 100 million adults born before 1991 remain unvaccinated, with many potentially at risk for infection. Chronic infection with the hepatitis B virus can cause liver damage and lead to cirrhosis and liver cancer.

Shingles, which is caused by the varicella zoster virus, affects one in three adults over their lifetime, according to the World Health Organization. In most people, shingles causes a painful, itchy rash but, in some cases, it can lead to long-term nerve pain, serious eye infections that can damage the vision, and, rarely, to dangerous inflammation of the brain.

 “Joining Sanofi will provide the global scale and expertise needed to maximise the impact of our vaccine portfolio. We believe Sanofi’s commercial reach, development capabilities and commitment to evidence-based immunisation 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,” said Ryan Spencer, Chief Executive Officer, Dynavax.

Apart from it, The US Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) to the company for the New Drug Application (NDA) of tolebrutinib to treat non-relapsing secondary progressive multiple sclerosis (nrSPMS) in adult patients.

On 15 December, 2025, Sanofi provided an update on the ongoing review which stated that FDA was expecting the review to go beyond the previously communicated revised US target action date of 28 December, 2025; further guidance from the FDA was expected by the end of the first quarter of 2026; and in response to an FDA request, Sanofi had submitted an expanded access protocol for tolebrutinib in nrSPMS. The announcement was based on the latest discussions with the FDA, which took place just before the update was provided.

“Today’s FDA decision is a significant and meaningful change in direction from the feedback the agency previously provided to Sanofi. We are very disappointed by the FDA's action. Disability progression remains a large unmet medical need in MS, and tolebrutinib was previously awarded breakthrough therapy designation by the FDA in recognition of its potential to address this critical gap. We believe that the FDA should also take the advice of scientific experts, clinicians, and patients in this matter to ensure all perspectives are considered. We remain committed to working with the FDA to find a path forward for tolebrutinib and ultimately serve the MS community,” said Houman Ashrafian, Executive Vice President, Head of Research and Development, Sanofi.

Tolebrutinib was provisionally approved in the United Arab Emirates in July 2025 for the treatment of non-relapsing secondary progressive multiple sclerosis and to slow disability accumulation independent of relapse activity in adults. It is currently under regulatory review in the EU and other jurisdictions worldwide.