Sanofi to Acquire Blueprint Medicines in $9.5 Billion Deal, Expanding Rare Immunological Disease Portfolio and Deepening Immunology Pipeline
In a landmark move to expand its presence in rare immunological diseases and strengthen its early-stage pipeline, French pharmaceutical giant Sanofi announced it will acquire U.S.-based Blueprint Medicines Corporation in a deal worth up to $9.5 billion. The acquisition is expected to significantly boost Sanofi’s capabilities in immunology, a therapeutic area the company has prioritized as a key pillar of its long-term growth strategy.
Blueprint Medicines, headquartered in Cambridge, Massachusetts, is a biopharmaceutical company known for its innovative work in precision therapies targeting systemic mastocytosis (SM) and other diseases driven by KIT gene mutations. The centerpiece of the acquisition is Blueprint’s lead medicine Ayvakit (known as Ayvakyt in Europe), the first and only approved therapy to target the underlying cause of advanced and indolent systemic mastocytosis, a debilitating and life-altering rare immunological condition.
Through this deal, Sanofi gains not only a commercially successful rare disease treatment with rapidly growing sales, but also a deep pipeline of next-generation investigational therapies, including elenestinib and BLU-808—two oral KIT inhibitors that could significantly broaden Sanofi’s reach across multiple inflammatory and immunologic disorders.
Expanding Sanofi’s Rare Disease and Immunology Franchise
Systemic mastocytosis is a rare disorder caused by the abnormal proliferation and accumulation of mast cells in various organs including the skin, bone marrow, liver, spleen, and gastrointestinal tract. The disease manifests in both advanced forms, which can be life-threatening, and indolent variants that cause a range of chronic, multisystem symptoms like anaphylaxis, bone pain, gastrointestinal issues, and severe fatigue. The majority of SM cases fall under the indolent category, making long-term disease management a critical need.
Ayvakit/Ayvakyt, an oral tyrosine kinase inhibitor, is approved by both the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for treating both advanced and indolent systemic mastocytosis. The therapy is designed to selectively target mutant forms of KIT and PDGFRA kinases, which play a central role in the pathology of SM and other KIT-driven diseases.
In 2024, Ayvakit generated $479 million in net sales and has continued on an upward trajectory into 2025, achieving nearly $150 million in revenue during the first quarter alone. This marks a greater than 60% year-over-year increase from the first quarter of 2024, underscoring the strong and growing demand for this precision therapy among allergists, immunologists, and hematologists.
“Blueprint’s innovative portfolio, particularly Ayvakit, directly complements our strategic focus in rare diseases and immunology,” said Sanofi CEO Paul Hudson. “With this acquisition, we’re taking a decisive step toward becoming the world’s leading immunology company. It enhances our pipeline, brings a commercially validated medicine with strong growth potential, and expands our presence among the key specialists treating immunological conditions.”
Pipeline Assets Strengthen Future Outlook
Beyond Ayvakit, the acquisition brings two critical pipeline candidates into Sanofi’s fold: elenestinib and BLU-808.
Elenestinib (BLU-263) is a next-generation KIT D816V inhibitor currently being studied in the HARBOR trial, a Phase 2/3 randomized, double-blind, placebo-controlled study evaluating its efficacy and safety in patients with indolent and smoldering systemic mastocytosis. Elenestinib is designed to have reduced central nervous system penetration, which may offer a more favorable safety profile for long-term use in chronic disease management.
The second investigational compound, BLU-808, is an oral wild-type KIT inhibitor engineered to be highly potent and selective. Unlike other inhibitors targeting mutant KIT, BLU-808 is designed to inhibit wild-type KIT, which plays a key role in mast cell activation involved in a broad spectrum of immunologic and inflammatory diseases. This opens the door to potential indications beyond systemic mastocytosis and provides a platform for further innovation in immunology.
“By integrating Blueprint’s scientific expertise in mast cell biology with our own R&D capabilities, we have the potential to significantly advance the treatment paradigm for numerous underserved diseases,” Hudson added.
Financial Terms and Structure of the Deal
Under the terms of the merger agreement, Sanofi will acquire Blueprint for $129.00 per share in cash, representing an equity value of approximately $9.1 billion. The offer reflects a 27% premium over Blueprint’s closing share price on May 30, 2025, and a 34% premium over the 30-day volume-weighted average price.
In addition to the upfront payment, Blueprint shareholders will receive one non-tradeable contingent value right (CVR) per share, entitling them to receive up to $6 per share based on the achievement of specific milestones related to BLU-808. The milestones include:
- A $2 per share payment upon the attainment of a clinical development milestone for BLU-808.
- An additional $4 per share payment upon achieving a regulatory milestone for the same candidate.
If all CVR milestones are met, the total consideration increases to approximately $9.5 billion on a fully diluted basis.
The acquisition will be executed through a tender offer for all outstanding Blueprint shares, followed by a merger of Blueprint into a wholly owned Sanofi subsidiary. Sanofi intends to finance the transaction using a mix of available cash and new debt. Importantly, the deal is not contingent on financing and is expected to close in the third quarter of 2025, pending regulatory and shareholder approvals.
Industry and Leadership Perspectives
For Blueprint Medicines, the acquisition by Sanofi represents both a validation of its scientific approach and an opportunity to scale its therapies globally.
“Since our founding, Blueprint Medicines has worked at the intersection of scientific innovation and operational excellence,” said Blueprint CEO Kate Haviland. “I’m incredibly proud of the medical breakthroughs we’ve delivered, particularly Ayvakit—the first and only medicine approved to treat the root cause of systemic mastocytosis. With Sanofi’s global reach and leadership in rare diseases, we’re poised to bring our medicines to more patients faster than ever before.”
The acquisition follows Sanofi’s broader strategy of focusing its R&D efforts on immunology, oncology, rare diseases, and vaccines. In recent years, the company has made a series of moves to reshape its pipeline, including divesting from less strategic areas and investing heavily in early-stage immunology programs and external innovation. The Blueprint acquisition is viewed as highly complementary to those efforts, adding both late-stage commercial assets and a strong early pipeline with multiple levers for future growth.
Sanofi also sees strategic alignment in Blueprint’s commercial infrastructure. The company has built strong relationships with allergists, dermatologists, and immunologists—specialist segments that are directly relevant to Sanofi’s existing and emerging immunology franchise, which includes treatments for atopic dermatitis, asthma, and type 1 diabetes.
Sanofi expects the acquisition to be immediately accretive to its gross margin and to have a positive impact on business operating income and earnings per share starting in 2026. The deal is not expected to significantly alter Sanofi’s financial guidance for 2025, but it provides long-term value by reinforcing the company’s leadership in rare immunological diseases.
With a market increasingly focused on targeted, precision-based treatments for rare and immune-mediated disorders, the addition of Blueprint’s innovative pipeline marks a pivotal enhancement to Sanofi’s capabilities. As the company continues its transformation into a science-driven biopharmaceutical leader, this acquisition solidifies its position at the forefront of immunology research and commercialization.
In summary, the Sanofi-Blueprint deal underscores the growing importance of rare immunological diseases in the pharmaceutical landscape and represents a calculated bet on the future of precision medicine. For patients living with systemic mastocytosis and other immunologic conditions, it brings renewed hope that scientific innovation, backed by scale and commitment, will deliver better therapies and improved outcomes in the years ahead.
