Shares of Dynamax Are Up Nearly 40% Today. Here's Why The Stock Is Flying

Key Takeaways Sanofi will pay $2.2 billion for Dynavax Techologies as it looks to add another Hepatitis B and new shingles vaccines to its portfolio. The deal will pay Dynavax investors $15.50 per share, a 39% premium from Tuesday's closing price. Shares of Dynavax Technologies ( DVAX ) skyrocketed after French drugmaker Sanofi ( SNY ) said it would buy the biopharmaceutical firm for $2.2 billion to expand its Hepatitis B offerings and enter the shingles vaccine market. Sanofi has agreed to buy Dynavax, news that sent the latter's shares higher Wednesday.Sheldon Cooper / SOPA Images / LightRocket via Getty Images Sanofi said it would be paying Dynavax investors $15.50 per share in cash, a 39% premium to its closing price yesterday. Dynavax shares were recently trading just a few cents below Sanofi's price for its shares. The transaction is expected to close in the first quarter of next year. Why This Matters to Investors One strategy of drug-development investors is to buy shares of companies they think are candidates for a buyout by bigger companies who either think they can help their products find larger markets, or believe their developmental treatments will soon prove more valuable as they move through testing. Dynavax currently has regulatory approval for its Heplisav-B Hepatitis B shot, a two-dose regimen for adults given over a month’s time. It also is in a Phase 1/2 trial of a shingles treatment called Z-1018, and has other candidates in the works. Thomas Triomphe, executive vice president of vaccines at Sanofi, said the additions of Heplisav-B and Z-1018 “bring new options to our portfolio and underscore our commitment to providing vaccine protection across the lifespan.” Sanofi said there is an “unmet need” for Hepatitis B and shingles treatments, as nearly 100 million people in the U.S. who were born before 1991 are unvaccinated. Dynavax CEO Ryan Spencer said the deal "will provide the global scale and expertise needed to maximize the impact of our vaccine portfolio." Shares of Dynavax have spent most of 2025 in negative territory, but with today’s gains they’re now up about 19% year-to-date. Do you have a news tip for Investopedia reporters? Please email us at [email protected]

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