Sanofi has announced an agreement to acquire Blueprint Medicines, a US-based biopharmaceutical company specializing in rare immunological diseases, including systemic mastocytosis (SM) and other KIT-driven conditions. The acquisition will give Sanofi access to Blueprint’s rare disease medicine Ayvakit (avapritinib), approved in both the US and the EU, along with an advanced immunology pipeline and a strong presence among allergists, dermatologists, and immunologists.
Ayvakit is currently the only approved treatment for advanced and indolent systemic mastocytosis, a rare disorder marked by the buildup and activation of abnormal mast cells in the bone marrow, skin, gastrointestinal tract, and other organs. The deal also includes elenestinib, a next-generation treatment for SM currently in phase 2/3 clinical trials, and BLU-808, a highly selective oral KIT inhibitor with potential applications across various immunological diseases.
Sanofi will pay \$129 per share in cash at closing, valuing Blueprint at approximately \$9.1 billion. In addition, Blueprint shareholders will receive a non-tradeable contingent value right (CVR), which offers potential milestone payments of \$2 and \$4 per share based on the successful development and regulatory approval of BLU-808. Including these potential payments, the deal’s total value could reach about \$9.5 billion.
Mast cells play a critical role in the immune system, releasing substances like histamines that contribute to inflammation. Systemic mastocytosis can cause severe symptoms such as anaphylaxis, bone disease, gastrointestinal problems, and skin lesions, significantly impacting patients’ quality of life. Indolent systemic mastocytosis represents the majority of cases.
Ayvakit generated net revenues of \$479 million in 2024 and nearly \$150 million in the first quarter of 2025, showing a growth rate of more than 60 percent compared to the same period last year. The drug works by inhibiting mutated KIT and PDGFRA proteins that drive disease progression.
Elenestinib is a selective KIT D816V inhibitor with limited penetration into the central nervous system. It is being tested in the HARBOR clinical trial to evaluate its safety and effectiveness in patients with indolent and smoldering systemic mastocytosis.
BLU-808, developed using Blueprint’s expertise in mast cell biology, targets wild-type KIT, a key protein involved in mast cell activation and linked to various inflammatory diseases.
The acquisition reflects Sanofi’s strategy to strengthen its immunology and rare disease portfolios. Sanofi CEO Paul Hudson said the deal will accelerate the company’s transformation into a leading immunology firm and complement recent acquisitions in early-stage medicines. He expressed enthusiasm about working with Blueprint’s team to advance scientific innovation and deliver new treatments to patients.
Blueprint Medicines CEO said the company is proud of its scientific achievements and its impact on patient care. He emphasized that joining forces with Sanofi will accelerate their shared mission to bring life-changing therapies to more patients worldwide.
The offer price represents a premium of about 27 percent over Blueprint’s closing stock price on May 30, 2025, and about 34 percent over its 30-day average trading price. Including the CVR, the total premium rises to approximately 33 percent and 40 percent, respectively.
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