Sanofi and Regeneron expanded their long-running antibody partnership with a deal worth up to $8 billion, adding four long-acting immunology candidates aimed at IL-13 and IL-4-related pathways. Sanofi will pay Regeneron a $1 billion upfront, with additional payments tied to development, regulatory, and commercial milestones. Regeneron will lead R&D, while Sanofi will handle global commercialization. The report notes that profit-sharing for Dupixent (dupilumab) remains unchanged, with the existing collaboration already covering multiple immunology indications and generating nearly $18 billion in sales last year. Among the newly disclosed assets is REGN20423, a long-acting IL-13 monoclonal antibody in Phase I for atopic dermatitis, alongside a long-acting IL-4xIL-13 bispecific and two additional long-acting antibodies targeting IL-4 and IL-4 receptor alpha. Regeneron also gains an option tied to Sanofi’s lunsekimig once Phase III completes. For the biotech sector, the strategic significance is the planned pipeline renewal ahead of potential patent cliff pressures, with both companies positioning next-generation long-acting molecules to extend competitive coverage in chronic type 2 inflammatory diseases.