Sanofi bags Blueprint to future-proof its immunology franchise

What happened

Today, Sanofi SA announced a definitive agreement to buy Blueprint Medicines (part of our portfolio) for $9.1bn cash plus up to $0.4 bn in CVRs tied to clinical milestones regarding Blueprint's latest asset, valuing the deal at $9.5 bn. Shareholders receive $129 per share, a 27 % premium to the prior close. 

The transaction is slated to close in Q3 2025, subject to customary approvals.

Impact on our Investment Case

Blueprint, an Atonra conviction since March 2023

Before the deal, Blueprint was a 3.6% position in our strategy. Our decision to enter a mid-portfolio conviction Q1 2023 was based on the following rationale:

• A "not so rare" Orphan disease: Ayvakit/Ayvakyt, Blueprint lead asset is the only approved therapy for advanced and indolent systemic mastocytosis (SM). SM is a rare disorder where a genetic defect keeps certain immune cells called mast cells stuck in overdrive, so they grow too many and spread throughout the body. Because mast cells release "alarm chemicals" like histamine, patients can experience unpredictable waves of flushing, itching, stomach cramps, bone pain, and even life-threatening allergic-type shocks. But better testing is showing that ~3–5 people per 100,000 may have SM - still an “orphan” disease, but larger than once thought. 
• A sizeable pricing and upside: Due to its orphan disease status, Blueprint can charge >$300k p.a., but given the lack of alternative therapies, payers are receptive. Blueprint’s first-mover status creates a solid advantage here, and it shows in the earnings. Q125 sales hit $149 m (+61 % y/y), and guidance was raised to $700-720mn for FY25, equivalent to a CY25 x12 EV/Sales (x17 FY2024) . Management consistently exceeded adoption curves and the market penetration estimation is still low at ~15 %, leaving ample runway.
• Optionality in the pipeline: Elenestinib, Blueprint's second asset, is a next-gen KIT inhibitor in phase 2/3 for indolent SM, which should secure Blueprint's position as the leader in SM. Far more interestingly, BLU-808, the earliest-stage drug, is an oral wild-type KIT inhibitor with potential across chronic urticaria, asthma, and other mast-cell disorders. 

Why Sanofi pulled the trigger

First, Sanofi needs revenue diversification from Dupixent. Dupixent generated ≈32 % of group sales in 2024; recent mixed COPD data underscores concentration risk. It is not just concentration; Dupixent expansion could also be slower than predicted. Meanwhile, Ayvakit offers a commercial asset growing >60 % y/y with 80 %+ gross margins, immediately accretive from 2026.

Second, Blueprint is a strategic immunology fit. Blueprint’s deep relationships with allergists/dermatologists overlap with Sanofi’s launch infrastructure for Dupixent and eczema/urticaria indications.

Pipeline optionality. Elenestinib could cannibalise Ayvakit but would extend SM leadership; BLU-808 opens multi-billion-dollar chronic-urticaria and asthma markets where Sanofi already markets Dupixent, enabling combo or sequencing strategies.

Lastly, Sanofi still has financial headroom. Even after Vigil and Blueprint acquisition, Sanofi retains net-debt (mid-2025)/EBITDA (2024) <1.5×, leaving room for further bolt-ons.

A synergy that other Big Pharmas are looking into

The acquisition brings not only late-stage and commercial programs but also a highly experienced team with deep expertise in kinase biology and rational drug design. Blueprint built its reputation by engineering selective kinase inhibitors tailored to genetically defined diseases.This deal should be read as more than just a pipeline acquisition. Sanofi is acquiring a precision design engine — and positioning itself for the next wave of small molecule innovation. The implications go beyond oncology. They touch immunology, rare disease, and platform infrastructure. And they highlight the growing value of companies that build scalable, repeatable systems for targeted drug discovery.

In some sense the parallels between Sanofi-Blueprint and Merck-SpringWorks is clear:

We keep expecting more of these bolt-on deals going forward.

M&A is looking better and worse than in 2024

After a subdued 2024, with zero deals above $5bn, 2025 now has two, with Sanofi securing the second spot. So far, 2025 is on par with 2021 for M&A commanding a premium of over 100%, and four deals away from the ATH of 2022. The digestion of the previous megadeals is finished, the FTC regulatory chill is lifting, the cost of capital could lower, and the election year is behind.

On a more bearish view, the multiple EV/Peak Sales for Blueprint is x2.5, whereas last year across all M&A, it stood at x2.8 and x3.1 the year before. Biotech assets are not getting more expensive, which is a boon for companies with the loss of exclusivity looming around the corner.

Furthermore, the new FDA commissioner Marty Makary has floated a conditional approval pathway that would let orphan drugs reach the market on persuasive mechanism-of-action data and single-arm studies, with rigorous post-market follow-up. In tiny patient populations that struggle to power randomised trials, this is expected to shave years and tens of millions off development costs. This new FDA stance to simplify market access for rare diseases only helps increase their attractiveness.

For a clearer picture, here is the list of M&A ordered by size since January 1st.

Our Takeaway

Sanofi locks in a fast-growing, under-penetrated rare-disease franchise and a pipeline in line with its immunology focus.

Big Pharma is on the hunt for post-2030 growth to replenish pipelines as the loss of exclusivity of virtually all their current blockbusters is impending. Today’s deal, the biggest rare-immunology buy-out in 2025, reinforces our conviction that assets in niche indications will continue commanding significant premiums, and we plan to reallocate the proceeds from the Blueprint acquisition within the rare diseases space.