[225Ac]-FPI-1434 + FPI-1175

**[225Ac]-FPI-1434 + FPI-1175** is a combination investigational therapy being evaluated primarily for advanced solid tumors expressing the insulin-like growth factor 1 receptor (IGF-1R). [225Ac]-FPI-1434 is a radiopharmaceutical that uses a humanized monoclonal antibody targeting IGF-1R, conjugated via a Fast-Clear linker to actinium-225, an alpha particle-emitting isotope that delivers targeted cytotoxic radiation to tumor cells. FPI-1175 is a cold (unlabeled) monoclonal antibody also targeting IGF-1R, administered prior to [225Ac]-FPI-1434 to saturate non-tumor IGF-1R “antigen sink,” thereby improving pharmacokinetics and increasing radiopharmaceutical uptake in tumors. This combination is being tested in a Phase 1 clinical study investigating the safety, tolerability, and dosimetry of pre-administered FPI-1175 before [225Ac]-FPI-1434 administration in patients with solid tumors, notably colorectal cancer, prostate cancer, and melanoma[1][2][3][5][6][7][9].