A logo on the Sanofi exhibition space at the Viva Technology conference dedicated to innovation and startups at Porte de Versailles exhibition center in Paris, France, on June 15, 2022.
Benoit Tessier | Reuters
Sanofi said on Wednesday it will buy U.S. biotech Dynavax Technologies for around $2.2 billion (1.9 billion euros) in an agreed deal that will add an adult hepatitis B vaccine and a promising experimental shingles shot to its portfolio.
The acquisition will help the French drugmaker diversify its vaccine business at a time when U.S. Health Secretary Robert F. Kennedy Jr. is remaking policy for childhood immunisation, industry analysts say.
The Trump administration has dropped a long-standing universal recommendation for hepatitis B vaccination in infants, drawing an outcry from the medical community, and is considering other changes for 2026.
Shares in Dynavax surged nearly 39% to $15.45 in U.S. trading hours on news of the deal. Sanofi shares eased 0.7%.
Seeking new revenue growth drivers
“We believe the acquisition makes sense given growing regulatory concerns around vaccines,” said William Blair analyst Matt Phipps.
“Sanofi is a logical acquisition partner for Dynavax given the company has extensive vaccine capabilities but the portfolio does not have an adult hepatitis B or shingles program.”
Sanofi has been seeking new products to drive revenue growth once its blockbuster asthma drug Dupixent goes off patent in 2031. It bought British private vaccine developer Vicebio for $1.5 billion in July after finalising an up to $9.5 billion deal for Blueprint Medicines.
It will pay $15.50 per Dynavax share, representing a 39% premium over the vaccine maker’s closing share price of $11.13 on Tuesday. Phipps said this was below his estimated value for the U.S. biotech’s hepatitis B shot, Heplisav-B, of $2.6 billion.
Sanofi will fund the deal using available cash, and expects to close the acquisition in the first quarter of 2026. The deal would not affect its 2025 financial outlook, it added.
Vaccine makers under pressure
Earlier this year, Sanofi and British rival GSK noted pressure in the U.S. flu vaccine market, while Australian biotech CSL delayed plans to spin off its vaccine division citing “heightened volatility” and a greater than expected decline in U.S. immunization rates.
Dynavax’s Heplisav‑B shot is given to those aged 18 years and older to help prevent infection from the hepatitis B virus. It is administered in two doses, one month apart, compared to other vaccines that are given in three doses over six months.
The shot generated $90 million in sales in the third quarter of 2025. Analysts expect peak annual sales of $609 million in the U.S.
The deal will also add an experimental shingles vaccine to Sanofi’s existing products that include flu and polio shots as well as the antibody therapy Beyfortus for the respiratory syncytial virus.
J.P. Morgan analysts said Dynavax’s experimental shot, Z-1018, could boost revenues beyond 2030 for Sanofi, if early data on its safety and effectiveness is replicated in larger trials.
It could take a share in the shingles market, where GSK’s top-selling Shingrix is on track to generate sales of 4 billion euros this year, the analysts added.
In August, Dynavax said its experimental shot generated a similar immune response as Shingrix, while showing a better safety profile, in a study of 92 people aged 50 to 69 years.
FDA rejects multiple sclerosis drug
Separately, Sanofi said the U.S. Food and Drug Administration had declined to approve its experimental drug tolebrutinib to slow disability progression in patients with a form of multiple sclerosis.
Houman Ashrafian, Sanofi’s head of research and development, said the news came as a surprise to the company, which had previously been told that the FDA review process would continue into the first quarter of 2026.
“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,” Ashrafian said in a press release.
The decision adds to a year of data from Sanofi’s experimental drugs for eczema and smoker’s lung that disappointed investors. Sanofi’s shares have largely underperformed the broader European sector index.
