Sanofi and Regeneron expanded their long-running antibody collaboration, pledging $1 billion upfront to develop four next-generation, long-acting immunology candidates aimed at the Dupixent (dupilumab) target space. The partners positioned the deal as a bid to maintain clinical and commercial momentum as patent timelines approach, with Regeneron set to lead R&D and Sanofi global commercialization. The expanded portfolio includes candidates targeting IL-13 and IL-4/IL-13 signaling, including REGN20423, a long-acting IL-13 antibody in Phase I testing for atopic dermatitis. The agreement also includes an option tied to Sanofi’s lunsekimig program after Phase III completion. For the sector, the move signals that large-cap players are continuing to “buy time” around blockbuster life cycles by financing next-generation biologics within proven research engines, rather than waiting for internal pipelines to mature from discovery.