Regeneron entered radiopharmaceutical development via a partnership with Telix Pharmaceuticals, a deal valued at up to $4.3 billion. The companies plan to co-develop and co-commercialize precision radiopharmaceutical therapies and companion diagnostics across up to eight solid tumor targets. The collaboration is structured around Regeneron’s antibody discovery platform (VelocImmune) and Telix’s radiopharmaceutical development, manufacturing, and supply chain capabilities. Regeneron emphasized combining its biologics expertise with radiopharma execution to broaden oncology modalities. Telix will receive an upfront payment of $40 million for four initial therapeutic programs, with options to expand the collaboration to additional programs. The companies described shared incentives through co-funding and milestone arrangements, with diagnostic commercialization aligned to Telix’s strengths. For the radiopharma market, the agreement signals how major antibody developers are moving beyond standalone radionuclide programs toward antibody-guided theranostic strategies with integrated diagnostics for patient selection and response monitoring.