Sanofi to acquire Blueprint Medicines, expanding portfolio in rare immunological disease and adding early-stage pipeline in immunology Adds fast-growing and only approved medicine for advanced and indolent

Blueprint Medicines, expanding portfolio in rare immunological disease and adding early-stage pipeline in immunology

Paris and Cambridge, MA. June 2, 2025. Sanofi and Blueprint Medicines Corporation (Blueprint), a US-based, publicly traded biopharmaceutical

company specializing in systemic mastocytosis (SM), a rare immunological disease, and other KIT-driven diseases, have entered into an

agreement under which Sanofi will acquire Blueprint.

The acquisition includes a rare immunology disease

medicine, Ayvakit/Ayvakyt (avapritinib), approved in the US and the EU, and a promising advanced and early-stage immunology pipeline.

Furthermore, Blueprint's established presence among allergists, dermatologists, and immunologists is expected to enhance Sanofi's

growing immunology pipeline.

Ayvakit/Ayvakyt is the only approved medicine for

advanced and indolent systemic mastocytosis (ASM & ISM), a rare immunology disease, which is characterized by the accumulation and

activation of aberrant mast cells in bone marrow, skin, the gastrointestinal tract, and other organs. The acquisition will also bring

elenestinib, a next-generation medicine for SM, as well as BLU-808, a highly selective and potent oral wild-type KIT inhibitor that has

the potential to treat a broad range of diseases in immunology.

Under the terms of the acquisition, Sanofi will pay

$129.00 per share in cash at closing, representing an equity value of approximately $9.1 billion. 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

transaction, including potential CVR payments, represents 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. 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."

CEO, Blueprint Medicines

"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."

Mast cells 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, mast cells release pro-inflammatory molecules such as histamines and proteases. 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 can include anaphylaxis, bone disease, gastrointestinal distress and skin lesions.

ISM represents the majority of SM cases.

Ayvakit achieved net revenues of $479 million in

2024 and nearly $150 million in Q1 2025, representing year-on-year growth of more than 60 percent over Q1 2024. 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 is a next-generation, potent and highly

selective KIT D816V inhibitor with limited central nervous system penetration. The oral investigational ISM medication is the subject

of HARBOR, a phase 2/3 study (clinical study identifier: NCT04910685). The ongoing, randomized, double-blind, 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 is an investigational oral,

highly potent and selective wild-type KIT inhibitor that was developed leveraging Blueprint's expertise in mast cell biology. Wild-type

KIT plays a central role in mast cell activation, which is implicated in a broad range of inflammatory diseases.

Transaction terms and financial

Under the terms of the merger agreement, Sanofi will

commence a cash tender offer to acquire all outstanding shares of Blueprint for $129.00 per share

in cash, reflecting a total equity value of approximately $9.1 billion. In addition, Blueprint's

shareholders will receive one non-tradeable CVR per Blueprint share with two potential milestone payments

The upfront offer price represents a premium of approximately

27% over the closing price of Blueprint on May 30, 2025 and a premium of approximately 34% over the

30 trading days volume weighted average price (VWAP) of Blueprint as of May 30, 2025. Together 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.

The consummation of the tender offer is subject to

customary closing conditions, including the tender of a number of shares of Blueprint common stock

representing at least a majority of the outstanding shares of Blueprint common stock, the receipt

of required regulatory approvals, and other customary conditions.

If the tender offer is successfully completed, a

wholly owned subsidiary of Sanofi will merge with and into Blueprint and all of the outstanding Blueprint

shares that are not tendered in the tender offer will be converted into the right to receive the same $129.00 per share in cash and one

CVR per share offered to Blueprint shareholders in the tender offer. Sanofi plans to finance the transaction

with a combination of cash on hand and proceeds from new debt. The tender offer is not subject to any financing condition. Subject

to the satisfaction or waiver of customary closing conditions, Sanofi currently expects to complete the acquisition in the third quarter

of 2025. The acquisition will not have a significant impact on Sanofi's financial guidance for 2025. It is immediately accretive

to gross margin and accretive to business operating income and EPS after 2026.

Conference call for investors

Sanofi will host a conference call for investors

and analysts at 08:30 CEST today. A presentation will be available for download from the Investor Relations section of sanofi.com before

the conference call starts.

The call will be held on Zoom with the following

Webinar ID: 979 9146 5119

Ayvakit (avapritinib) is the first and only medicine

approved by the US Food and Drug Administration (FDA) to treat the root cause of SM. It was FDA approved for the treatment of advanced

SM in June 2021 and indolent SM in May 2023. It now is indicated in adults with ISM, adults with advanced SM, including aggressive SM

(ASM), SM with an associated hematological neoplasm (SM-AHN) and mast cell leukemia (MCL), and adults with unresectable or metastatic

gastrointestinal stromal tumor (GIST) harboring a PDGFRA exon 18 mutation, including PDGFRA D842V mutations. The medicine is approved

in the EU as Ayvakyt for the treatment of adults with ISM with moderate to severe symptoms inadequately controlled on symptomatic

treatment, adults with ASM, SM-AHN or MCL, after at least one systemic therapy, and adults with unresectable or metastatic GIST harboring

the PDGFRA D842V mutation. Globally, the medicine is approved for one or more indications in 16 countries, including China where it is

marketed by CStone Pharmaceuticals, paying tiered percentage royalties on sales.

Sanofi is an R&D driven, AI-powered biopharma

company committed to improving people's lives and creating compelling growth. We apply our deep understanding of the immune system

to invent medicines and vaccines that treat and protect millions of people around the world, with an innovative pipeline that could benefit

millions more. Our team is guided by one purpose: we chase the miracles of science to improve people's lives; this inspires

us to drive progress and deliver positive impact for our people and the communities we serve, by addressing the most urgent healthcare,

environmental, and societal challenges of our time. Sanofi is listed on EURONEXT: SAN and NASDAQ: SNY

About Blueprint Medicines

is a global, fully integrated biopharmaceutical company that invents life-changing medicines. We seek to alleviate human suffering by

solving important medical problems in two core focus areas: allergy/inflammation and oncology/hematology. Our approach begins by targeting

the root causes of disease, using deep scientific knowledge in our core focus areas and drug discovery expertise across multiple therapeutic

modalities. We have a track record of success with two approved medicines, including Ayvakit/Ayvakyt (avapritinib) which we are bringing

to patients with SM in the US and Europe. Leveraging our established research, development, and commercial capability and infrastructure,