177Lu-FO-004

177Lu-FO-004 is an investigational targeted radioligand therapy (RLT) developed by 3B Pharmaceuticals GmbH for the treatment of advanced solid tumors. The therapeutic agent consists of a ligand, FO-004, which specifically targets fibroblast activation protein (FAP), labeled with the beta-emitting radioisotope lutetium-177 (177Lu). FAP is highly expressed in the tumor microenvironment, particularly on cancer-associated fibroblasts (CAFs) across various solid tumor types, while showing limited expression in normal adult tissues. By binding to FAP, 177Lu-FO-004 delivers localized cytotoxic radiation directly to the tumor stroma, aiming to inhibit tumor growth and alter the tumor microenvironment. It is currently being evaluated in Phase 1 clinical trials, often in conjunction with a companion diagnostic PET imaging agent, 68Ga-3BP-3940, to facilitate patient selection and dosimetry.