Sanofi and Regeneron expand immunology partnership to the tune of $8bn

Sanofi will pay Regeneron $1bn upfront plus up to $7bn in milestones under an expanded immunology partnership worth up to $8bn, co-developing and co-commercialising four long-acting antibodies targeting IL-13, IL-4, an IL-4xIL-13 bispecific and IL-4Rα. The IL-13 antibody REGN20423 is in a Phase I study in atopic dermatitis, with the other three expected to enter clinical studies in 2027. Regeneron leads R&D, Sanofi leads commercialisation, costs and profits are split evenly, and the companies also settled their 2024 litigation over Dupixent, which earned $18.3bn in 2025 sales.