TARRYTOWN, New York, and PARIS, France, October 1, 2026

Regeneron Pharmaceuticals, Inc. and Sanofi have expanded their long-standing global antibody collaboration to include four next-generation, long-acting immunology antibodies designed to target pathways involved in type 2 inflammation and immune-mediated diseases. The expanded alliance adds REGN20423, a clinical-stage long-acting IL-13 monoclonal antibody, along with a long-acting IL-4xIL-13 bispecific antibody and two additional preclinical antibodies targeting IL-4 and IL-4 receptor alpha (IL-4Rα). Under the agreement, Regeneron will receive $1 billion upfront, with the potential for up to $7 billion in additional development, regulatory and commercial milestone payments. The companies will share development and commercialization costs and future profits equally on a global basis.

Four Long-Acting Antibodies Added to Alliance

The expanded collaboration focuses on antibody medicines designed to provide longer-acting immunology treatment options while targeting established biological pathways associated with type 2 inflammation. REGN20423, a long-acting monoclonal antibody directed against interleukin-13 (IL-13), is currently being evaluated in a Phase 1 clinical trial for atopic dermatitis. The second program is a long-acting IL-4xIL-13 bispecific antibody, while the other two preclinical programs target IL-4 and IL-4Rα. According to the companies, the three programs that have not yet entered clinical development are expected to begin clinical studies in 2027. The programs build on the scientific experience gained from the companies’ development of Dupixent® (dupilumab), which targets IL-4 and IL-13 signaling and has been approved across multiple type 2 inflammatory diseases.

$1 Billion Upfront Payment and Shared Development

Under the expanded license and collaboration agreement, Sanofi will pay Regeneron $1 billion upfront, with potential additional payments of up to $7 billion tied to development, regulatory and commercial milestones. The companies will share the costs associated with developing and commercializing the new antibody programs and will divide potential future profits 50:50 globally. Regeneron will lead research and development activities, while Sanofi will lead global commercial efforts if the investigational medicines successfully reach the market. The companies said the existing profit-sharing arrangement for Dupixent will remain unchanged. The agreement also includes an option for Regeneron to add Sanofi’s lunsekimig, an investigational bispecific Nanobody VHH therapy targeting TSLP and IL-13, to the collaboration after completion of its Phase 3 trials in chronic obstructive pulmonary disease.

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Building on a More Than 20-Year Partnership

The expanded alliance builds on a collaboration between Regeneron and Sanofi that began in 2003 and has produced multiple medicines, including Dupixent. The companies said more than 1.5 million people are currently receiving Dupixent across nine indications, reflecting the scale of their existing immunology franchise. Dupixent is a fully human monoclonal antibody that inhibits signaling through the IL-4 and IL-13 pathways, which are important drivers of type 2 inflammation. The companies are now applying their combined antibody discovery, development and commercial capabilities to a new generation of long-acting candidates. The parties have also settled their prior collaboration-related litigation as part of the broader development of their relationship. The newly expanded collaboration remains focused on investigational medicines, and the clinical-stage and preclinical antibodies included in the agreement have not been established as safe or effective for future indications by regulatory authorities. The upcoming clinical development of REGN20423 and the anticipated 2027 entry of the other three antibody programs will provide additional data on their potential applications in immunology and inflammatory diseases. The agreement therefore represents an expansion of the companies’ ongoing antibody development platform while maintaining their established collaboration around Dupixent.

Source: Regeneron, Sanofi press release