Regeneron Pharmaceuticals (NASDAQ: REGN) and Sanofi (EURONEXT: SAN, NASDAQ: SNY) announced an expansion of their existing antibody collaboration, adding four long-acting immunology antibodies to their alliance.

Under the terms of the agreement, Regeneron will receive a $1 billion upfront payment, with potential milestone payments of up to an additional $7 billion.

The two companies will co-develop and co-commercialize four Regeneron-invented antibodies targeting interleukin-13 (IL-13), IL-4xIL-13 bispecific, interleukin-4 (IL-4), and interleukin-4 receptor alpha (IL-4Rα). Development and commercialization costs, as well as future profits, will be split equally between the two companies. Regeneron will lead research and development, while Sanofi will lead global commercial efforts.

One of the four antibodies, REGN20423, a long-acting IL-13 monoclonal antibody, is currently in a Phase 1 clinical trial for atopic dermatitis. The remaining three antibodies are expected to enter clinical studies in 2027. Regeneron also holds an option to include Sanofi's lunsekimig, an investigational bispecific therapy targeting TSLP and IL-13, upon completion of its Phase 3 trials for chronic obstructive pulmonary disease.

The existing profit-sharing arrangement for Dupixent (dupilumab), the companies' jointly developed IL-4/IL-13 inhibitor currently approved in more than 60 countries across nine indications, will remain unchanged. More than 1.5 million patients are currently receiving Dupixent worldwide.

The companies also disclosed that prior collaboration-related litigation between them has been settled.