French pharmaceutical giant Sanofi announced Monday its agreement to acquire Blueprint Medicines Corporation, a US-based biopharmaceutical company specializing in systemic mastocytosis treatments, for $9.1 billion in cash. The strategic acquisition significantly expands Sanofi's rare disease and immunology portfolio while adding a fast-growing approved therapy and promising pipeline assets.
Transaction Details and Financial Terms
Under the merger agreement, Sanofi will pay $129.00 per share in cash at closing, representing an equity value of approximately $9.1 billion. The offer price reflects a premium of approximately 27% over Blueprint's closing price on May 30, 2025, and approximately 34% over the 30-day volume weighted average price.
Blueprint shareholders will also receive one non-tradeable contingent value right (CVR) per share, entitling holders to two potential milestone payments: $2 per CVR for achieving a clinical development milestone for BLU-808, and $4 per CVR for achieving a regulatory milestone for the same compound. Including potential CVR payments, the total transaction value reaches approximately $9.5 billion on a fully diluted basis.
"The proposed acquisition of Blueprint Medicines represents a strategic step forward in our rare and immunology portfolios," said Paul Hudson, CEO of Sanofi. "It enhances our pipeline and accelerates our transformation into the world's leading immunology company."
Key Asset: Ayvakit/Ayvakyt
The centerpiece of the acquisition is Ayvakit/Ayvakyt (avapritinib), the first and only approved medicine for treating the root cause of systemic mastocytosis. The oral therapy achieved net revenues of $479 million in 2024 and nearly $150 million in Q1 2025, representing year-on-year growth of more than 60% over Q1 2024.
Ayvakit/Ayvakyt is approved by the FDA for treating advanced systemic mastocytosis (June 2021) and indolent systemic mastocytosis (May 2023). The drug is indicated for adults with indolent systemic mastocytosis, advanced systemic mastocytosis including aggressive systemic mastocytosis, systemic mastocytosis with an associated hematological neoplasm, mast cell leukemia, and certain gastrointestinal stromal tumors. The medicine is approved for one or more indications in 16 countries globally.
Understanding Systemic Mastocytosis
Systemic mastocytosis is a rare immunologic disorder characterized by the accumulation and activation of aberrant mast cells in bone marrow, skin, the gastrointestinal tract, and other organs. The condition can lead to debilitating symptoms across multiple organ systems, significantly impacting patients' quality of life. Symptoms include anaphylaxis, bone disease, gastrointestinal distress, and skin lesions, with indolent systemic mastocytosis representing the majority of cases.
Mast cells normally play an important 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, these cells release pro-inflammatory molecules such as histamines and proteases.
Pipeline Assets and Future Potential
The acquisition brings two promising investigational compounds to Sanofi's portfolio. Elenestinib is a next-generation, potent and highly selective KIT D816V inhibitor with limited central nervous system penetration. The oral investigational medication is currently being evaluated in HARBOR, a phase 2/3 randomized, double-blind, placebo-controlled study (NCT04910685) designed to assess efficacy and safety in patients with indolent systemic mastocytosis and smoldering systemic mastocytosis.
BLU-808 represents a potentially transformative asset as an investigational oral, highly potent and selective wild-type KIT inhibitor. Developed leveraging Blueprint's expertise in mast cell biology, BLU-808 targets wild-type KIT, which plays a central role in mast cell activation implicated in a broad range of inflammatory diseases.
Strategic Rationale and Market Position
Kate Haviland, CEO of Blueprint Medicines, emphasized the strategic fit: "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."
Blueprint's established presence among allergists, dermatologists, and immunologists is expected to enhance Sanofi's growing immunology pipeline. The acquisition complements Sanofi's recent focus on early-stage medicine acquisitions while maintaining capacity for additional strategic transactions.
Financial Impact and Timeline
Sanofi plans to finance the transaction through a combination of cash on hand and proceeds from new debt, with no financing condition attached to the tender offer. The acquisition is expected to close in the third quarter of 2025, subject to customary closing conditions including regulatory approvals and the tender of at least a majority of Blueprint's outstanding shares.
The transaction will not significantly impact Sanofi's financial guidance for 2025 but is expected to be immediately accretive to gross margin and accretive to business operating income and earnings per share after 2026. Hudson noted that Sanofi retains sizeable capacity for further acquisitions, indicating continued strategic expansion plans in the immunology space.
