Sanofi, Regeneron deepen $8bn antibody pact

Sanofi and Regeneron (REGN) announced on October 1, 2026 that they are expanding their long-standing antibody collaboration to include multiple next-generation, long-acting immunology antibodies. The new agreement is structured as a global alliance and is centered on adding four Regeneron-invented programs targeting key inflammatory pathways.

Under the expanded collaboration, Sanofi will pay Regeneron an upfront payment of $1 billion. The deal also includes potential development, regulatory and commercial milestone payments of up to an additional $7 billion, bringing the total potential value of the agreement to as much as $8 billion.

The alliance expansion brings four long-acting Regeneron-invented antibody programs into the collaboration. These include REGN20423, described as a long-acting IL-13 monoclonal antibody, an IL-4xIL-13 bispecific antibody, an IL-4-targeting antibody, and an IL-4Rα-targeting antibody. All are designed for immunology indications.

REGN20423 is currently in a Phase 1 clinical trial for atopic dermatitis. The other three antibody candidates are expected to enter clinical studies in 2027, positioning the partners for a staggered clinical development timeline across the portfolio.

For the newly added programs, Sanofi and Regeneron will equally share development and commercialization costs. Future global profits from these antibodies will also be split 50:50 between the two companies, maintaining a balanced economic structure for the alliance.

Within this framework, Regeneron will lead research and development activities for the new assets. Sanofi will take charge of global commercial efforts, reflecting the companies’ established division of responsibilities in their existing collaboration.

The agreement provides Regeneron with an option to include Sanofi’s investigational bispecific therapy lunsekimig in the collaboration. Lunsekimig is described as a bispecific VHH therapy targeting TSLP and IL-13, with the option exercisable upon completion of its Phase 3 trials for chronic obstructive pulmonary disease.

The companies stated that the expanded agreement resolves prior collaboration-related litigation. At the same time, the existing arrangements for their marketed product Dupixent remain unchanged, with the partners citing more than 1.5 million active patients worldwide on Dupixent.

To discuss the expanded alliance, Sanofi and Regeneron scheduled a conference call for investors and analysts on October 1, 2026 at 8:00 a.m. ET / 14:00 CET. The call is intended to provide further details on the new antibody programs, financial terms, and strategic priorities within the collaboration.