Sanofi expands antibody partnership with Regeneron in US$8B deal to strengthen immunology pipeline
Sanofi will pay Regeneron US$1 billion upfront, with development, regulatory, and commercial milestones potentially adding another US$ 7 billion.
USA—Sanofi and Regeneron Pharmaceuticals have expanded their antibody development partnership in a deal worth up to US$8 billion as they seek to develop new treatments ahead of Dupixent’s anticipated loss of exclusivity.
The agreement builds on more than two decades of collaboration between the French pharmaceutical company and the US biotechnology firm.
Their partnership produced Dupixent (dupilumab), an anti-inflammatory medicine that generated US$18.3 billion in global sales in 2025.
The expanded deal aims to advance four additional antibodies for potential use in immunological diseases.
Four antibodies enter expanded collaboration
Under the agreement, the companies will jointly develop and commercialise four long-acting antibodies discovered by Regeneron.
The candidates target interleukin-13 (IL-13), interleukin-4 (IL-4), the IL-4 receptor alpha (IL-4Rα), and a bispecific antibody designed to inhibit both IL-4 and IL-13.
Sanofi will pay Regeneron US$1 billion upfront, with development, regulatory, and commercial milestones potentially adding another US$ 7 billion.
The companies will share development and commercialisation costs, as well as profits from any resulting approved medicines.
Regeneron will lead research and development, while Sanofi will oversee global commercialisation.
This arrangement builds on the partners’ established division of responsibilities while extending their collaboration into additional immunology programmes.
REGN20423, the IL-13 antibody, is undergoing a Phase I clinical trial for atopic dermatitis.
The other three candidates are expected to enter clinical studies in 2027.
The agreement also gives Regeneron an option to include Sanofi’s investigational bispecific nanobody therapy, lunsekimig, which targets thymic stromal lymphopoietin (TSLP) and IL-13.
The option becomes exercisable after completion of the therapy’s Phase III studies for chronic obstructive pulmonary disease (COPD).
Dupixent’s future shapes pipeline strategy
Dupixent has expanded into several indications since its initial approval in 2017.
Sales increased by 25% in 2025 to US$18.3 billion, making the medicine a significant contributor to Sanofi’s pharmaceutical business.
However, investors are monitoring the prospect of patent expirations beginning in 2031.
Developing new immunology medicines could help the companies establish additional revenue streams, although the clinical and regulatory timelines for the new antibodies remain uncertain.
Citi analysts described the expanded agreement as “a step in the right direction” but noted that the move was largely expected.
They also cautioned that the candidates’ early development stages could prevent them from reaching the market before Dupixent loses exclusivity.
Companies settle legal dispute
The announcement also resolves a dispute between the partners.
Regeneron sued Sanofi in 2024, alleging a lack of transparency in Dupixent’s commercialisation.
The companies confirmed that they had settled the litigation alongside the expanded collaboration.
Sanofi’s shares rose 2.7% at the Paris market open on October 1 compared with the September 30 close.
The company had a reported market capitalisation of €87.5 billion, or about US$102 billion.
The agreement marks an early milestone for Sanofi CEO Belén Garijo, who succeeded Paul Hudson in April 2026.
Regeneron CEO Leonard Schleifer said the expanded alliance would help advance new long-acting antibodies towards the potential global impact achieved by Dupixent.
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