Dynavax (DVAX) Shares Plunge 1.70% Amid Regulatory and Legal Risks in Sanofi Deal

The share price fell to its lowest level this month, with an intraday decline of 1.70%.

Dynavax Technologies (DVAX) faces renewed uncertainty as its stock trades near a 2025 low amid the pending $2.2 billion all-cash acquisition by Sanofi. The $15.50-per-share offer, a 39% premium to pre-announcement levels, initially drove a 37% pre-market surge, but recent volatility reflects concerns over regulatory hurdles and shareholder litigation. Sanofi’s bid, set to close in Q1 2026, hinges on regulatory approvals and a 75% shareholder tender threshold, creating a timeline-dependent valuation scenario for investors. The deal’s certainty is further tested by legal challenges questioning whether the price fairly compensates shareholders, with two law firms investigating potential fiduciary breaches by Dynavax’s board.

Analysts highlight the strategic logic behind Sanofi’s move, citing Dynavax’s hepatitis B vaccine (HEPLISAV-B) and shingles candidate (Z-1018) as key assets. HEPLISAV-B’s two-dose regimen offers a competitive edge in adult immunization markets, while Z-1018’s potential to replicate Shingrix’s efficacy with reduced side effects could enhance Sanofi’s vaccine portfolio. Despite Dynavax’s strong pre-acquisition financials—including $94.9 million in Q3 revenue and $647.8 million in cash reserves—the stock’s post-announcement trajectory remains tied to merger-arbitrage dynamics. A deal collapse could shift focus back to standalone fundamentals, though litigation risks and regulatory delays pose near-term headwinds. With Christmas Eve closing U.S. markets early, liquidity constraints may amplify short-term swings as investors weigh the probability of closure against renegotiation threats.