Dynavax (DVAX) Stock Surges in Premarket on $2.2B Sanofi Buyout

Dynavax Technologies Corporation (NASDAQ: DVAX) experienced a dramatic surge in premarket trading on Wednesday, December 24, 2025, following the announcement that French pharmaceutical giant Sanofi has agreed to acquire the U.S.-based vaccine maker for approximately $2.2 billion in cash. The stock jumped to $15.50 in premarket trading at 9:09 AM EST, representing a massive 39.26% gain from its previous close of $11.13.

The acquisition, which values Dynavax at nearly 70% above its market capitalization of $1.31 billion, marks Sanofi’s latest strategic move to expand its adult immunization portfolio and diversify growth beyond its blockbuster asthma drug Dupixent.

Sanofi Offers $15.50 Per Share in All-Cash Transaction

Sanofi will pay $15.50 per share in cash for all outstanding shares of Dynavax, representing a 39% premium over the company’s closing price on December 23, 2025, and a 46% premium over its three-month volume-weighted average price.

The transaction has been unanimously approved by Dynavax’s board of directors, with Sanofi planning to fund the acquisition using available cash resources. The deal is expected to close in the first quarter of 2026, subject to customary conditions including the tender of at least a majority of outstanding Dynavax shares and regulatory approvals.

The acquisition comes as part of Sanofi’s aggressive expansion strategy in 2025, following the purchase of UK biotech firm Vicebio for $1.5 billion and the finalization of an up to $9.5 billion deal for U.S.-based rare disease drugmaker BluePrint Medicines.

Thomas Triomphe, Executive Vice President of Vaccines at Sanofi, stated that Dynavax enhances Sanofi’s adult immunization presence by adding differentiated vaccines that complement the company’s existing expertise. Centerview Partners LLC and Goldman Sachs & Co. LLC are serving as financial advisors to Dynavax, with Cooley LLP acting as legal counsel.

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Dynavax Assets Strengthen Sanofi’s Adult Immunization Strategy

The acquisition will give Sanofi immediate access to HEPLISAV-B, Dynavax’s marketed hepatitis B vaccine that differentiates itself with a two-dose regimen administered over one month, compared to competing vaccines requiring three doses over six months.

Additionally, Sanofi gains a Phase 1/2 shingles vaccine candidate (Z-1018) that analysts believe could potentially capture market share from GSK’s dominant Shingrix, which is projected to generate approximately 4 billion euros in sales this year. J.P. Morgan analysts noted that the experimental shingles vaccine offers potential upside if early trial data can be replicated in larger studies.

Dynavax, a commercial-stage biopharmaceutical company with 405 full-time employees, reported strong third-quarter 2025 earnings that significantly exceeded expectations, with earnings per share of $0.21 beating forecasts by 61.54%. The company generated $94.9 million in revenue for the quarter, slightly above the anticipated $94.41 million.

Ryan Spencer, Chief Executive Officer of Dynavax, stated that joining Sanofi would provide the global scale and expertise needed to maximize the impact of their vaccine portfolio. The company’s 52-week trading range has been $9.20 to $14.63, with a market beta of 0.88.

Disclaimer: The author does not hold or have a position in any securities discussed in the article. All stock prices were quoted at the time of writing.