Sanofi Acquires Blueprint Medicines in $9.5B Strategic Move to Expand Rare Disease and Immunology Capabilities

Sanofi has announced a definitive agreement to acquire Blueprint Medicines for $129 per share in an all-cash transaction, valuing the biopharmaceutical company at approximately $9.1 billion upfront. Including potential contingent payments tied to development milestones, the total deal value reaches $9.5 billion on a fully diluted basis. This represents a 27% premium over Blueprint’s closing price on May 30, 2025, and a 34% premium based on the 30-day weighted average trading price.

Why This Deal Matters

The acquisition strengthens Sanofi’s position in the competitive rare disease and immunology sectors. Blueprint Medicines brings an established network among allergists, dermatologists, and immunologists—relationships Sanofi can leverage to accelerate its growing immunology pipeline. More importantly, the deal adds a commercially proven therapeutic to Sanofi’s portfolio.

“The proposed acquisition of Blueprint Medicines represents a strategic step forward in our rare and immunology portfolios,” said Paul Hudson, Sanofi’s CEO. “This acquisition is fully aligned with our strategic intent to strengthen our existing therapeutic areas and bring relevant and differentiated medicines to patients while securing attractive returns to our shareholders.”

The Crown Jewel: Ayvakit/Ayvakyt

The star of Blueprint Medicines’ portfolio is Ayvakit (avapritinib), the first and only approved medicine to treat the underlying cause of systemic mastocytosis. The oral therapeutic targets activated KIT and PDGFRA mutant kinases, addressing a rare immunological disorder characterized by abnormal mast cell accumulation and activation across multiple organ systems.

Ayvakit generated impressive commercial traction: $479 million in net revenues during 2024, with nearly $150 million in Q1 2025 alone—representing year-on-year growth exceeding 60% compared to Q1 2024. The medicine is approved in the US and EU for advanced and indolent systemic mastocytosis, as well as certain gastrointestinal stromal tumors harboring specific genetic mutations.

Early-Stage Pipeline Potential

Beyond Ayvakit’s commercial success, Blueprint contributes a promising pipeline of investigational therapies. Elenestinib, a next-generation KIT D816V inhibitor, is advancing through a phase 2/3 trial (HARBOR study) evaluating its efficacy and safety in patients with indolent and smoldering systemic mastocytosis. The compound’s limited blood-brain barrier penetration makes it a more selective option.

BLU-808, an oral wild-type KIT inhibitor, offers potential across a broad spectrum of inflammatory and immunological diseases. Wild-type KIT plays a central role in mast cell activation, suggesting applications well beyond systemic mastocytosis.

Transaction Structure and Timeline

Sanofi will launch a tender offer at $129 per share, with Blueprint shareholders also receiving one non-tradeable contingent value right (CVR) per share. The CVRs entitle holders to potential milestone payments of $2 per share upon a BLU-808 clinical development milestone and $4 per share upon a regulatory milestone.

The company plans to finance the transaction through existing cash and new debt issuance, with no financing conditions attached to the offer. Sanofi expects to complete the acquisition in Q3 2025. The deal is immediately accretive to gross margin and will become accretive to business operating income and EPS after 2026, with no material impact on Sanofi’s 2025 financial guidance.

The Strategic Rationale

Kate Haviland, CEO of Blueprint Medicines, emphasized the alignment: “Since our founding, Blueprint has worked at the intersection of scientific innovation and operational excellence. With this agreement, we begin our next chapter with Sanofi, whose exceptional leadership in rare disease and immunology and proven ability to scale medical solutions stand to accelerate our joint mission to bring life-changing medicines to patients worldwide.”

This acquisition signals Sanofi’s commitment to deepening its presence in immunology—a high-growth therapeutic area. By absorbing Blueprint’s specialized expertise in mast cell biology and established relationships within the immunology ecosystem, Sanofi gains both immediate revenue accretion and a platform for future pipeline expansion. The deal is expected to close in the third quarter of 2025, pending standard closing conditions and regulatory approvals.