Sanofi and Regeneron expanded their long-standing antibody alliance with a new deal worth up to $8 billion, centered on developing next-generation long-acting immunology drugs that build on the same pathways behind Dupixent (dupilumab). Under the agreement, Regeneron receives $1 billion upfront, with up to $7 billion tied to development, regulatory and commercial milestones. The companies will share development and costs 50:50 and split future profits globally on a 50:50 basis, with Regeneron leading R&D and Sanofi owning global commercialization. The collaboration adds multiple long-acting candidates, including REGN20423 (an IL-13 monoclonal antibody in Phase 1 for atopic dermatitis), along with a long-acting IL-4xIL-13 bispecific and additional long-acting antibodies targeting IL-4 and IL-4 receptor alpha. Sanofi also gains an option framework around Regeneron bringing in lunsekimig after a Phase 3 readout.