Sanofi to acquire Dynavax for $2.2B, sending shares higher by 37%

Shares of Dynavax Technologies jumped sharply in premarket trading on Wednesday after the US vaccine maker agreed to be acquired by French pharmaceutical group Sanofi in an all-cash deal valued at about $2.2 billion.

Sanofi said it will pay $15.50 per share for Dynavax, representing a premium of roughly 39% to the company’s closing price on Tuesday and about 46% to its three-month volume-weighted average price.

Dynavax shares rose more than 37% in premarket trading to around $15.31 following the announcement.

The transaction is expected to close in the first quarter of 2026, subject to customary regulatory approvals.

Deal details and market reaction

Under the terms of the agreement, Sanofi will acquire the Emeryville, California-based company for approximately $2.2 billion, or €1.9 billion.

Dynavax had a market capitalisation of about $1.31 billion as of Tuesday’s close, according to LSEG data.

Sanofi said it will fund the acquisition using available cash and that the transaction will have no impact on its financial outlook for 2025.

The company’s shares were little changed in early trading, while Dynavax’s stock surged to reflect the takeover premium.

Broker sentiment on Dynavax had already been broadly positive before the deal.

According to LSEG data, three of the four brokerages covering the stock rated it “buy” or higher, while one had a “sell” recommendation.

Strategic expansion of Sanofi’s vaccine portfolio

The acquisition gives Sanofi access to Dynavax’s portfolio of vaccine assets, including its approved adult hepatitis B vaccine in the US market.

It also adds an experimental shingles vaccine that is currently in early-stage clinical development.

In August, Dynavax reported that its shingles vaccine candidate generated an immune response comparable to GlaxoSmithKline’s blockbuster shingles shot, Shingrix, while demonstrating a potentially better safety profile in an early-to-mid-stage study.

Sanofi said the assets will be integrated into its existing vaccine pipeline, strengthening its position in preventive medicines.

The deal comes as the French drugmaker seeks to diversify growth beyond its blockbuster asthma treatment Dupixent, which has been a key driver of earnings in recent years.

The company has pursued a series of acquisitions in 2025 to broaden its portfolio.

In July, Sanofi agreed to buy British private biotech firm ViceBio for $1.5 billion, underlining its focus on expanding through targeted deals.

Broader context and regulatory backdrop

The Dynavax acquisition was announced on the same day Sanofi disclosed a regulatory setback.

Separately, the company said the US Food and Drug Administration had declined to approve its experimental drug tolebrutinib for the treatment of a form of multiple sclerosis.

Despite that development, Sanofi maintained that the Dynavax deal would not affect its near-term financial guidance.

The company said the acquisition aligns with its longer-term strategy of reinforcing its vaccine and immunology businesses through external innovation.

For Dynavax, the agreement marks a significant exit at a substantial premium, following years of development focused on vaccines.

If completed as planned, the transaction will fold the US company’s assets into one of Europe’s largest pharmaceutical groups, further consolidating the global vaccines market.

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