Sanofi and Blueprint Medicines, a US-based, publicly traded biopharmaceutical company specializing in systemic mastocytosis (SM), a rare immunological disease, as well as other KIT-driven diseases, have entered into an agreement under which Sanofi will acquire Blueprint.
This acquisition includes a rare immunology disease medicine, Ayvakit/Ayvakyt (avapritinib), approved in the US and the EU, as well as an advanced and early-stage immunology pipeline. And Blueprint’s established presence among allergists, dermatologists, and immunologists is expected to enhance Sanofi’s immunology pipeline.
Ayvakit/Ayvakyt is the only approved medicine for advanced and indolent systemic mastocytosis (ASM & ISM), a rare immunological disease characterized by the accumulation and activation of aberrant mast cells in the bone marrow, skin, gastrointestinal tract, and other organs. The deal will also bring elenestinib, a next-generation medicine for SM, as well as BLU-808. This highly selective and potent oral wild-type KIT inhibitor has the potential to treat a broad range of diseases in immunology.
Under the terms of the deal, Sanofi will pay $129 per share in cash at closing, representing an equity value of about $9.1 billion. And Blueprint shareholders also will receive one non-tradeable contingent value right (CVR) – which will entitle the holder to receive two potential milestone payments of $2 and $4 per CVR for the achievement, respectively, of future development and regulatory milestones for BLU-808. The total equity value of the deal (including potential CVR payments) represents approximately $9.5 billion on a fully diluted basis.
Mast cells: Mast cells play a significant role in immune responses and are typically found in tissues that encounter the external environment, such as the skin, lungs, and gastrointestinal tract. Upon activation, mast cells release pro-inflammatory molecules, including histamines and proteases. And systemic mastocytosis is a rare immunologic disorder that can lead to a range of debilitating symptoms across multiple organ systems and a significant impact on patients’ quality of life. The symptoms that patients with SM experience include anaphylaxis, bone disease, gastrointestinal distress, and skin lesions. ISM represents the majority of SM cases.
Ayvakit: Ayvakit achieved net revenues of $479 million last year and nearly $150 million in Q1 2025, representing year-on-year growth of more than 60% over Q1 2024. And the oral medicine is a potent and selective inhibitor of activated KIT and PDGFRA mutant kinases. In certain diseases, mutations in KIT and PDGFRA force protein kinases into an increasingly active state and Ayvakit/Ayvakyt is designed to bind and inhibit these proteins.
Elenestinib: Elenestinib is a next-gen, potent and highly selective KIT D816V inhibitor with limited central nervous system penetration. And the oral investigational ISM medication is the subject of HARBOR, a phase 2/3 study (clinical study identifier: NCT04910685). The ongoing, randomized, double-blind, and placebo-controlled study is designed to evaluate the efficacy and safety of elenestinib plus symptom-directed therapy in patients with ISM and smoldering SM.
BLU-808: BLU-808 is an investigational oral, highly potent and selective wild-type KIT inhibitor that was developed leveraging Blueprint’s expertise in mast cell biology. And wild-type KIT plays a central role in mast cell activation, which is implicated in a broad range of inflammatory diseases.
Merger terms: Under the terms of the merger, Sanofi will commence a cash tender offer to acquire all outstanding shares of Blueprint for $129 per share in cash, reflecting a total equity value of approximately $9.1 billion. And Blueprint’s shareholders will receive one non-tradeable CVR per Blueprint share with two potential milestone payments as follows:
— $2 per share, conditioned upon the achievement of a clinical development milestone for BLU-808, and
— $4 per share, conditioned upon the achievement of a regulatory milestone for BLU-808.
The upfront offer price represents a premium of about 27% over the closing price of Blueprint on May 30, 2025 and a premium of about 34% over the 30 trading days volume weighted average price (VWAP) of Blueprint as of May 30, 2025. Along with the CVR, the premium is approximately 33% over the closing price on May 30, 2025 and approximately 40% over the 30 trading days VWAP.
KEY QUOTES:
“The proposed acquisition of Blueprint Medicines represents a strategic step forward in our rare and immunology portfolios. It enhances our pipeline and accelerates our transformation into the world’s leading immunology company. This acquisition is fully aligned with our strategic intent to strengthen our existing therapeutic areas, to bring relevant and differentiated medicines to patients and to secure attractive returns to our shareholders. It complements recent acquisitions of early-stage medicines that remain our main field of interest. Sanofi still retains a sizeable capacity for further acquisitions. We are excited to welcome Blueprint’s talented people and we look forward to chasing the miracles of science together. This makes sense for science, for both companies, for healthcare professionals, and – most of all – for patients.”
Paul Hudson, CEO, Sanofi
“Since our founding, Blueprint Medicines has worked at the intersection of scientific innovation and operational excellence. I’m incredibly proud of the medical innovations our people have created and delivered to patients. We have translated our unique scientific understanding of mast cell biology into a portfolio of important therapies including Ayvakit – the first and only medicine approved to treat the root cause of systemic mastocytosis – and worked collaboratively with communities to improve standards of care and patient outcomes. With this agreement, we begin our next chapter with Sanofi, whose exceptional leadership in rare disease and immunology and proven ability to solve medical challenges at scale stand to accelerate our joint mission to bring life-changing medicines to many more patients around the world.”
Kate Haviland, CEO, Blueprint Medicines
