Sanofi is expanding its decade-long antibody partnership with Regeneron by adding four long-acting immunology candidates under an up-to-$8 billion collaboration. The companies will share development and commercialization costs equally, with 50:50 profit splitting globally, while Regeneron will lead R&D and Sanofi will handle global commercial execution. The agreement builds on the companies’ flagship IL-4/IL-13 asset Dupixent (dupilumab), which continues to drive revenue across multiple indications. Among the new programs is REGN20423, a long-acting IL-13 antibody in Phase I for atopic dermatitis, along with a long-acting IL-4xIL-13 bispecific and additional long-acting IL-4 pathway options. Management framed the expansion as a step toward next-generation, longer-duration biologics targeting type 2 inflammation, with the goal of sustaining momentum as the immunology market evolves. The deal underscores how next-wave differentiation is increasingly focused on dosing convenience and duration rather than wholly new targets.