Sanofi to Acquire Dynavax, Adding a Marketed Adult Hepatitis B Vaccine and Phase 1/2 Shingles Candidate to the Pipeline

Rhea-AI Summary

Sanofi (acquirer) will acquire Dynavax (Nasdaq: DVAX) for $15.50 per share in cash, representing ~$2.2 billion equity value and a 39% premium to Dynavax's Dec 23, 2025 close. The offer funds the marketed adult hepatitis B vaccine HEPLISAV-B (two-dose regimen) and Dynavax's phase 1/2 shingles candidate Z-1018, plus additional pipeline projects.

The transaction is unanimously approved by the Dynavax board, is expected to close in Q1 2026 subject to customary conditions including majority tender, HSR clearance, and foreign regulatory approvals, and will be funded from Sanofi cash resources.

Positive

• $15.50 cash per share offer
• Equity value of approximately $2.2 billion
• 39% premium to Dec 23, 2025 closing price
• HEPLISAV-B marketed in US with two-dose regimen
• Z-1018 shingles candidate in phase 1/2 development
• Expected close in Q1 2026 (subject to conditions)

Negative

• Tender offer requires a majority of outstanding shares
• Transaction subject to HSR antitrust clearance
• Subject to additional foreign regulatory filings and clearances
• Completion risk from potential competing offers or unmet conditions

Key Figures

Cash offer price $15.50 per share Tender offer consideration per DVAX share

Equity value approximately $2.2 billion Total equity value implied by transaction

Offer premium vs close 39% premium Premium over DVAX closing price on December 23, 2025

Premium vs 3-month VWAP 46% premium Premium over 3‑month VWAP as of December 23, 2025

Unvaccinated adults nearly 100 million adults US adults born before 1991 remaining unvaccinated for hepatitis B

Shingles lifetime risk one in three adults Adults affected by shingles over a lifetime

HEPLISAV-B doses two doses over one month Adult hepatitis B vaccine dosing schedule

Adverse reaction window within 7 days Timeframe for common adverse reactions after vaccination

Market Reality Check

$15.38 Last Close

Volume Volume 1,302,666 is below the 20-day average of 1,624,933 ahead of the acquisition news. normal

Technical Shares traded above the 200-day MA of 10.76 with a pre-news price of 11.13.

Peers on Argus

Peers showed mixed moves, with changes from -2.9% (AMPH) to +3.24% (TLRY), indicating today’s acquisition news is company-specific rather than a coordinated sector move.

Historical Context

Date	Event	Sentiment	Move	Catalyst
Nov 19	Conference participation	Neutral	-2.3%	Announcement of participation in the Evercore Healthcare Conference.
Nov 05	Earnings and buyback	Positive	+2.5%	Q3 2025 results plus new $100M share repurchase program.
Nov 05	COVID-19 license deal	Positive	+2.5%	Exclusive license for Vaxart’s oral COVID-19 vaccine program.
Oct 22	Earnings scheduling	Neutral	+0.4%	Notice of upcoming Q3 2025 earnings report and call.
Oct 21	Clinical trial update	Positive	+0.3%	Positive topline Part 1 data for Z-1018 shingles vaccine trial.

Pattern Detected

Recent news events were operational and clinical updates with relatively modest single-day price moves, offering limited precedent for a large acquisition premium.

Recent Company History

Over the last few months, Dynavax reported Q3 2025 financials with growing HEPLISAV-B revenue and a new share repurchase program, advanced its shingles candidate Z-1018 with positive Phase 1/2 data, and entered an exclusive license for an oral COVID-19 vaccine program. Additional items included conference participation and scheduling of earnings. These events reflected a maturing commercial franchise and expanding pipeline, which provide context for Sanofi’s decision to acquire the company at a cash premium.

Market Pulse Summary

The stock surged +38.2% in the session following this news. A strong positive reaction aligns with the sizeable cash premium offered, including an offer price of $15.50 per share and a stated equity value of approximately $2.2 billion. Historically, Dynavax’s news flow featured incremental clinical and financial updates with modest price moves, so a large spike would reflect the step-change nature of a strategic buyout. Investors would need to consider execution risks around closing conditions and arbitrage dynamics once the stock trades near the offer price.

Key Terms

tender offer financial

"Sanofi will commence a cash tender offer to acquire all outstanding shares"

A tender offer is a proposal made by a person or company to buy shares from existing shareholders at a set price, usually higher than the current market value, within a specific time frame. It matters to investors because it can lead to a change in ownership or control of a company, and shareholders must decide whether to sell their shares at the offered price.

volume-weighted average price financial

"a premium of approximately 46% over the 3-month volume-weighted average price (VWAP)"

Volume-weighted average price (VWAP) is the average price of a stock over a specific time period where each trade is weighted by the number of shares traded, so larger trades influence the average more than small ones. Investors and traders use VWAP as a reference point to judge whether trades are happening at relatively good or poor prices—like checking the average price paid for an item at a market where bulk purchases count more than single-item buys.

vwap financial

"premium of approximately 46% over the 3-month volume-weighted average price (VWAP)"

VWAP, or Volume-Weighted Average Price, is a way to find the average price of a stock throughout the trading day, giving more importance to times when more shares are traded. It helps traders see the typical price and decide whether a stock is expensive or cheap compared to its average, similar to finding the average speed during a trip by giving more weight to times when you traveled faster or slower.

phase 1/2 clinical development medical

"Z-1018), which is currently in phase 1/2 clinical development"

A phase 1/2 clinical development program combines the first human testing of a drug (phase 1), which checks safety and appropriate dose, with an early look at whether the drug shows signs of benefit (phase 2). For investors, these trials are an early milestone: they move a product from lab work into humans, reduce some scientific uncertainty, and provide the first data that can sharply change a company’s value — like a test-drive that reveals if a prototype is roadworthy and promising.

toll-like receptor medical

"Dynavax's vaccine adjuvant, a toll-like receptor (TLR) 9 agonist, to enhance"

Toll-like receptors are proteins on immune cells that act like smoke detectors, sensing bits of bacteria, viruses or cell damage and triggering an alarm that starts an immune response. They matter to investors because drugs or vaccines that activate or block these receptors can change how well a treatment works, influence clinical trial outcomes, and become valuable therapeutic or diagnostic assets in biotech and pharmaceutical pipelines.

tlr 9 agonist medical

"vaccine adjuvant, a toll-like receptor (TLR) 9 agonist, to enhance the immune"

A TLR9 agonist is a drug or compound that activates a specific immune sensor called Toll-like receptor 9, which helps kick-start the body’s innate immune response. Think of it as pressing the alarm button in the immune system to attract and focus immune cells; investors care because these agents can boost vaccines or cancer therapies, influence clinical trial outcomes, regulatory risk, development costs, and potential market value.

adjuvant medical

"hepatitis B surface antigen with Dynavax's vaccine adjuvant, a toll-like receptor"

An adjuvant is an ingredient added to a vaccine or other therapy to strengthen or shape the body’s response to the main active component, like a helper that makes the primary ingredient work better or longer. For investors, adjuvants matter because they can change how well a product performs, alter dosing and safety profiles, affect regulatory review, and therefore influence clinical success, market size and competitive advantage.

prescribing information medical

"Talk to your healthcare provider to determine if HEPLISAV-B is right for you.Please see full Prescribing Information"

Official prescribing information is the detailed, government‑approved document that explains what a medicine is, how to use it, who should or should not take it, and what risks to watch for — like the instructions and warnings that come with a product. Investors care because these instructions determine how widely a drug can be used, what claims can be made, and how regulators or courts may view safety and effectiveness, all of which directly affect sales, market access and liability.

AI-generated analysis. Not financial advice.

Dynavax stockholders to receive $15.50 in cash, a 39% premium to Dynavax closing share price on
December 23, 2025

EMERYVILLE, Calif., Dec. 24, 2025 /PRNewswire/ -- Sanofi announced today that it has entered into an agreement to acquire Dynavax Technologies Corporation (Nasdaq: DVAX), a publicly traded vaccines company with a marketed adult hepatitis B vaccine (HEPLISAV-B®) and a differentiated shingles vaccine candidate. The acquisition augments Sanofi's presence in adult immunization 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 1/2 clinical development, and additional vaccine pipeline projects.

"Dynavax enhances Sanofi's adult immunization presence by adding differentiated vaccines that complement Sanofi's expertise," said Thomas Triomphe, Executive Vice President, Vaccines, Sanofi. "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."

"Joining Sanofi will provide the global scale and expertise needed to maximize the impact of our vaccine portfolio," said Ryan Spencer, Chief Executive Officer, Dynavax. "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. We are confident that this transaction – and the compelling value it provides – is in the best interests of the Company and its stockholders."

Dynavax believes hepatitis B and shingles represent a significant 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, dangerous inflammation of the brain.

Financial considerations
Under the terms of the merger agreement, Sanofi will commence a cash tender offer to acquire all outstanding shares of Dynavax for $15.50 per share in cash, reflecting a total equity value of approximately $2.2 billion.

The offer price represents a premium of approximately 39% over the closing price of Dynavax on December 23, 2025 and a premium of approximately 46% over the 3-month volume-weighted average price (VWAP) of Dynavax as of December 23, 2025.

The transaction has been unanimously approved by the Dynavax board of directors. The consummation of the tender offer is subject to customary closing conditions, including the tender of a number of shares of Dynavax common stock that represent at least a majority of the outstanding shares of Dynavax common stock, the expiration or termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, certain foreign regulatory filings and clearances and other customary conditions.

If the tender offer is successfully completed, then following the successful completion of the tender offer, a wholly owned subsidiary of Sanofi will merge with and into Dynavax, and all of the outstanding Dynavax common stock that are not tendered in the tender offer will be converted into the right to receive the same $15.50 per share in cash offered to Dynavax shareholders in the tender offer.

Sanofi plans to fund the acquisition with available cash resources. Subject to the satisfaction or waiver of customary closing conditions, the transaction is expected to close in the first quarter of 2026.

Centerview Partners LLC and Goldman Sachs & Co. LLC are acting as financial advisors to Dynavax, and Cooley LLP is acting as its legal counsel.

About HEPLISAV-B
HEPLISAV-B is an adult hepatitis B vaccine that combines hepatitis B surface antigen with Dynavax's vaccine adjuvant, a toll-like receptor (TLR) 9 agonist, to enhance the immune response.

HEPLISAV-B is a shot given to adults 18 years of age and older to help prevent infection caused by the hepatitis B virus. HEPLISAV-B is usually given in the arm muscle. HEPLISAV-B is given in two doses, one month apart, by a healthcare provider.

IMPORTANT SAFETY INFORMATION
Do not administer HEPLISAV-B to individuals with a history of severe allergic reaction (e.g., anaphylaxis) after a previous dose of any hepatitis B vaccine or to any component of HEPLISAV-B, including yeast.

Appropriate medical treatment and supervision must be available to manage possible anaphylactic reactions following administration of HEPLISAV-B.

Immunocompromised persons, including individuals receiving immunosuppressant therapy, may have a diminished immune response to HEPLISAV-B.

Hepatitis B has a long incubation period. HEPLISAV-B may not prevent hepatitis B infection in individuals who have an unrecognized hepatitis B infection at the time of vaccine administration.

The most common patient-reported adverse reactions reported within 7 days of vaccination were injection site pain (23%-39%), fatigue (11%-17%), and headache (8%-17%).

There are no adequate and well-controlled studies of HEPLISAV-B in pregnant individuals. Available data, primarily in individuals who received one dose of HEPLISAV-B in the 28 days prior to or during pregnancy, do not suggest an increased risk of major birth defects and miscarriage.

It is not known whether HEPLISAV-B is excreted in human milk.

Data are not available to assess the effects of HEPLISAV-B on the breastfed infant or on milk production/excretion.

Vaccination with HEPLISAV-B may not result in protection of all vaccine recipients.

Talk to your healthcare provider to determine if HEPLISAV-B is right for you.
Please see full Prescribing Information

About Dynavax
Dynavax is a commercial-stage biopharmaceutical company developing and commercializing innovative vaccines to help protect the world against infectious diseases. Dynavax has two commercial products, HEPLISAV-B® vaccine [Hepatitis B Vaccine (Recombinant), Adjuvanted], which is approved in the U.S., the European Union and the United Kingdom for the prevention of infection caused by all known subtypes of hepatitis B virus in adults 18 years of age and older, and CpG 1018® adjuvant. For more information about Dynavax's marketed products and development pipeline, visit www.dynavax.com.

Dynavax Note Regarding Forward-Looking Statements
Certain statements either contained in or incorporated by reference into this press release, other than purely historical information, including statements relating to the sale of Dynavax and any statements relating to Dynavax's business and expected operating results, and the assumptions upon which those statements are based, are "forward-looking statements." These forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions, and include words such as "believes," "plans," "anticipates," "projects," "estimates," "expects," "intends," "strategy," "future," "opportunity," "may," "will," "should," "could," "potential," or similar expressions. Such forward-looking statements include those relating to the ability to complete and the timing of completion of the transactions contemplated by the Agreement and Plan of Merger dated as of December 23, 2025 by and among Dynavax, Samba Merger Sub, Inc., and Sanofi (the "Merger Agreement") including the parties' ability to satisfy the conditions to the consummation of the tender offer and the other conditions set forth in the Merger Agreement, including the time and benefits thereof, and the possibility of any termination of the Merger Agreement; potential effect of the merger on Dynavax's clinical pipeline, market share and beliefs that hepatitis B and shingles represent significant adult vaccination opportunities and important public health needs, and other statements that are not historical facts. The forward-looking statements contained in this document are based on current expectations and assumptions that are subject to risks and uncertainties which may cause actual results to differ materially from the forward-looking statements. Actual results and the timing of events may differ materially from those anticipated in such forward-looking statements because of risks associated with uncertainties which include, without limitation, risks related to the timing of the tender offer and the subsequent merger; whether sufficient stockholders of Dynavax will tender their shares in the tender offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the offer or the merger may not be satisfied or waived, including that a governmental entity may prohibit, delay or refuse to grant approval for the consummation of the tender offer or the merger; risks associated with acquisitions, such as the risk that the effects of disruption from the transactions of Dynavax's business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees and business partners; as well as other risks related to Dynavax's businesses detailed in Dynavax's public filings with the SEC from time to time, including the most recent Annual Reports on Form 10-K for the year ended December 31, 2024, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K. The reader is cautioned not to unduly rely on these forward-looking statements. Dynavax expressly disclaims any intent or obligation to update or revise publicly these forward-looking statements except as required by law.

Additional Information for US Shareholders and Where to Find It

The tender offer for the outstanding shares of Dynavax common stock referenced in this communication has not yet commenced. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell shares of Dynavax, nor is it a substitute for the tender offer materials that Sanofi and its acquisition subsidiary will file with the U.S. Securities and Exchange Commission (the "SEC") upon commencement of the tender offer. At the time the tender offer is commenced, Sanofi and its acquisition subsidiary will file tender offer materials on Schedule TO, and Dynavax will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. The tender offer materials (including an Offer to Purchase, a related Letter of Transmittal and certain other tender offer documents) and the Solicitation/Recommendation Statement will contain important information. HOLDERS OF SHARES OF DYNAVAX ARE URGED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT DYNAVAX STOCKHOLDERS SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES. The Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, will be made available to all holders of shares of Dynavax at no expense to them. The tender offer materials and the Solicitation/Recommendation Statement will be made available for free at the SEC's web site at www.sec.gov. Additional copies may be obtained for free on Dynavax's website at https://investors.dynavax.com/sec-filings.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, Sanofi files annual and special reports and other information with the SEC and Dynavax files annual, quarterly and special reports and other information with the SEC. You may read and copy any reports or other information filed by Sanofi and Dynavax at the SEC public reference room at 100 F. Street, N.E., Washington D.C. 20549. Please call the Commission at 1-800-SEC-0330 for further information on the public reference room. Sanofi's and Dynavax's filings with the SEC are also available to the public from commercial document-retrieval services and at the website maintained by the SEC at www.sec.gov.

Dynavax Media and Investor Relations:
Paul Cox
Vice President, Investor Relations and Corporate Communications
pcox@dynavax.com
510-665-0499

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SOURCE Dynavax Technologies

FAQ

What price is Sanofi offering for Dynavax (DVAX) and what premium does it represent?

Sanofi is offering $15.50 per share in cash, representing about a 39% premium to Dynavax's Dec 23, 2025 closing price.

What assets does Sanofi acquire with Dynavax (DVAX)?

Sanofi acquires marketed adult hepatitis B vaccine HEPLISAV-B, the phase 1/2 shingles candidate Z-1018, and additional pipeline projects.

When is the Dynavax (DVAX) acquisition expected to close?

Subject to customary conditions and clearances, the transaction is expected to close in Q1 2026.

How will Sanofi fund the acquisition of Dynavax (DVAX)?

Sanofi plans to fund the acquisition using its available cash resources.

What regulatory and shareholder conditions must be met for the DVAX deal to complete?

The deal requires a majority tender of shares, expiration of the HSR waiting period, and certain foreign regulatory clearances.

What clinical stage is Dynavax's shingles vaccine Z-1018 in after the Sanofi announcement?

Z-1018 is in phase 1/2 clinical development.