Regeneron and Telix announced a partnership valued at up to $4.3 billion to co-develop and co-commercialize next-generation radiopharmaceutical therapies and companion diagnostics. Under a cost-and-profit sharing structure, the companies will pair Regeneron’s antibody discovery portfolio generated through VelocImmune with Telix’s radiopharmaceutical development, manufacturing, and global supply chain capabilities. The collaboration targets up to eight solid tumor targets and includes a diagnostics strategy intended for patient selection and treatment-response assessment. Telix receives an upfront payment for initial therapeutic programs, with options to expand the deal to additional programs. The announcement marks Regeneron’s first direct foray into radiopharmaceutical development alongside its immunotherapy portfolio, positioning the companies to compete in the growing antibody–theranostic interface for solid tumors.