Regeneron and Sanofi Expand Antibody Alliance in $8 Billion Deal
Regeneron and Sanofi have expanded their long-standing collaboration with an $8 billion deal to co-develop four next-generation immunology drugs.
Regeneron Pharmaceuticals and Sanofi announced the expansion of their antibody collaboration on October 1, 2026. The deal, with a total potential value of $8 billion, includes an upfront $1 billion payment to Regeneron and up to $7 billion in additional development, regulatory, and commercial milestone payments.
Scientific scope and pipeline
The collaboration adds four next-generation, long-acting antibodies invented by Regeneron. These target key drivers of type 2 inflammation: interleukin-13 (IL-13), IL-4, and IL-4 receptor alpha (IL-4Rα). The alliance aims to develop new immune system-regulating drugs similar to the partners' blockbuster, Dupixent.
The most advanced candidate is REGN20423, an IL-13 antibody currently in a Phase I clinical trial for atopic dermatitis, also known as eczema. The other three investigational antibodies are in preclinical development and are expected to enter clinical studies in 2027.
| Candidate | Target | Development Stage | Indication (Current Trial) |
|---|---|---|---|
| REGN20423 | IL-13 | Phase I | Atopic dermatitis (eczema) |
| Other 1 | IL-4xIL-13 bispecific | Preclinical | Expected in clinic 2027 |
| Other 2 | IL-4 | Preclinical | Expected in clinic 2027 |
| Other 3 | IL-4Rα | Preclinical | Expected in clinic 2027 |
Development and commercialization model
Under the expanded agreement, Regeneron will lead research and development activities for the new programs. Sanofi will lead global commercialization efforts. Development and commercialization costs will be shared equally, and future profits from any resulting products will also be split 50:50 globally. The existing profit-sharing arrangement for dupilumab (Dupixent) remains unchanged.
Strategic context and alliance history
The expansion builds on a Regeneron-Sanofi collaboration dating to 2003, an alliance that has lasted more than 20 years. It has jointly established Dupixent as a leading treatment for diseases driven by type 2 inflammation, with IL-4 and IL-13 established as central drivers. Dupixent was first cleared for market in 2017 for eczema and has since received approvals for asthma, COPD, and several chronic conditions affecting the skin, throat, and nose. More than 1.5 million people are currently receiving Dupixent across nine indications.
Leonard S. Schleifer, board co-chair, president and chief executive officer of Regeneron, said, "The Regeneron-Sanofi alliance has been one of the most productive in biopharma history." The expansion aims to bring next-generation immunology medicines to patients faster and may help address upcoming patent challenges for the current franchise. The companies have also settled prior collaboration-related litigation. Also, Regeneron has the option to include Sanofi's experimental medicine lunsekimig in the collaboration after it completes certain late-stage studies.
REGN20423 is currently in an early-stage clinical trial for eczema treatment, with the other three antibodies expected to enter human testing in 2027.
