The news: Sanofi and Regeneron are expanding their immunology partnership. Sanofi will pay $1 billion upfront and up to $7 billion in milestone payments for four next-generation drug candidates. Regeneron will lead R&D, and Sanofi will lead commercialization. The deal builds on the companies’ longstanding Dupixent partnership and settles a lawsuit Regeneron filed in late 2024 over Sanofi’s transparency around Dupixent.

Zooming out: Partnerships like Regeneron and Sanofi’s pair one drugmaker’s science with another’s clinical or commercial reach. Bristol Myers Squibb and Pfizer similarly partnered on blockbuster blood thinner Eliquis (discovered by BMS and commercialized by Pfizer), while Moderna and Merck are working on personalized cancer vaccines, pairing Moderna’s technology with Merck’s clinical and business infrastructure.

Why it matters: The new deal and drug candidates give Sanofi and Regeneron a pathway to replace their blockbuster success from Dupixent, as its US patents will begin to expire in 2031. However, it’s unclear whether the duo’s four new drug candidates will reach the market before Dupixent loses exclusivity. For context on Dupixent’s pharma market significance: It is approved for nine conditions including asthma, eczema and COPD and is expected to reach $21.6 billion in sales this year—making it the world’s fourth best selling drug, per Evaluate data provided to EMARKETER.

Implications for pharma immunology brands: Rivals can now plan around four potential immunology drugs coming from proven collaborators. The deal also gives competitors an early view of the commercial pressure they could face if those drugs reach the market.

Sanofi and Regeneron could eventually shift D2C spending from Dupixent to successful follow-ons, a playbook already used in immunology as AbbVie shifted significant ad support from Humira to next-generation drugs Skyrizi and Rinvoq. Dupixent has ranked among the top TV drug ad spenders every year since 2020, including $241 million in national TV spending in 2025, showing how much advertising weight Sanofi and Regeneron could put behind successors.

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