Sanofi agreed to acquire Dynavax Technologies for $2.2 billion in cash, buying a commercial hepatitis B vaccine (Heplisav‑B) and a phase I/II shingles candidate, according to company announcements reported by MedCity News. The deal closes immediately increased Sanofi’s vaccine footprint and adds an on‑market product that complements its existing portfolio. The transaction arrives alongside a regulatory setback: Sanofi disclosed a complete response letter (CRL) for tolebrutinib, its experimental multiple sclerosis drug, creating a near‑term development headwind while the company expands by acquisition. The juxtaposition of inorganic growth and a clinical disappointment underscores shifting tactical priorities in big‑pharma vaccine and neuroimmunology strategies.