Sanofi and Regeneron expand immunology alliance with four new long-acting antibodies

Deal structure and financial commitments

Sanofi will pay Regeneron $1 billion upfront and up to $7 billion in potential development, regulatory and commercial milestones to bring four new long-acting antibodies under their existing antibody collaboration. The companies will equally share development and commercialization costs and split future profits from the new programs 50:50 globally. Regeneron will lead research and development activities, while Sanofi will lead global commercial efforts. The existing profit-sharing arrangement for Dupixent will remain unchanged.

Scope of the expanded collaboration

The four added programs are Regeneron-invented antibodies targeting interleukin-13 (IL-13), an IL-4xIL-13 bispecific, interleukin-4 (IL-4) and interleukin-4 receptor alpha (IL-4Rα). The lead candidate, the long-acting IL-13 monoclonal antibody REGN20423, is currently in a Phase 1 clinical study for atopic dermatitis; the other three antibodies are slated to begin clinical studies in 2027. Regeneron will also have the option to include Sanofi's investigational bispecific Nanobody VHH therapy lunsekimig, which targets TSLP and IL-13, upon completion of its Phase 3 trials for chronic obstructive pulmonary disease.

Strategic context for both companies

The expanded agreement builds on the more than 20-year antibody collaboration that has delivered Dupixent (dupilumab), used by more than 1.5 million patients across nine indications and characterized in the announcement as a leading treatment for diseases driven by type 2 inflammation. Sanofi described the deal as an early step in its innovation strategy ahead of Dupixent's eventual loss of patent protection. Sanofi's Chief Executive Officer Belén Garijo said the deeper collaboration is intended to accelerate the development of next-generation therapies for immune-mediated diseases and to contribute to Sanofi's long-term future. Regeneron's Board co-Chair, President and Chief Executive Officer Leonard S. Schleifer, MD, PhD, said the expansion positions the new long-acting antibodies to achieve rapid, global impact similar to Dupixent.

Other developments

Separately, a Thomson Reuters report noted that Sanofi's shares rose about 2 percent in early trading following the announcement. The same report indicated that earlier litigation between the two companies over the collaboration has been settled, and that Jefferies described the deal as a proactive early signal from Sanofi's new chief executive regarding pipeline uncertainty ahead of Dupixent's patent expiry.

Upcoming milestone

Sanofi and Regeneron are scheduled to host a conference call for investors and analysts on October 1, 2026, at 14:00 CET/8:00 am ET. A presentation is accessible from the investor relations areas of sanofi.com and regeneron.com when the call begins.