Sanofi and Regeneron Expand Immunology Collaboration in Deal Worth Up to $8 Billion

On October 1, 2026, Sanofi and Regeneron Pharmaceuticals, Inc. (“Regeneron”) announced an expansion of their existing immunology collaboration to develop and commercialize four long-acting antibodies. Sanofi will pay Regeneron $1 billion upfront, with up to an additional $7 billion in development, regulatory, and commercial milestone payments.

The four antibodies target interleukin-13 (“IL-13”), interleukin-4 (“IL-4”), interleukin-4 receptor alpha (“IL-4Rα”), and both IL-4 and IL-13 through a bispecific antibody. The IL-13 antibody, REGN20423, is in a phase 1 study for atopic dermatitis. The companies expect the other three antibodies to enter clinical studies in 2027. Regeneron will also have an option to add Sanofi’s investigational TSLP/IL-13 bispecific Nanobody® VHH therapy, lunsekimig, to the collaboration after completion of its phase 3 studies for chronic obstructive pulmonary disease.

Regeneron will lead research and development, while Sanofi will lead global commercialization. The companies will share development and commercialization costs and split any future profits from the new programs equally. Their existing profit-sharing arrangement for DUPIXENT® (dupilumab) will remain in place.

The announcement also states that Sanofi and Regeneron have settled their prior collaboration-related litigation.

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