Actinium-225 FAPI-XT

225Ac-FAPI-XT is an investigational targeted alpha therapy (TAT) that utilizes the alpha-emitting radionuclide Actinium-225 conjugated to the FAPI-XT ligand. The drug is designed to target Fibroblast Activation Protein (FAP), a cell-surface protease heavily expressed on cancer-associated fibroblasts (CAFs) which constitute a significant portion of the tumor stroma in various epithelial cancers. Developed by researchers at Heidelberg University Hospital, the FAPI-XT ligand is an optimized derivative of earlier FAPI molecules (such as FAPI-04 and FAPI-46) engineered specifically to increase tumor residence time and enhance the therapeutic window. Actinium-225 provides high-energy, short-range alpha particles that cause dense ionization and lethal double-strand DNA breaks in FAP-expressing cells and nearby tumor cells through a bystander effect. This mechanism of action is intended to bypass conventional treatment resistance in patients with advanced solid tumors, including pancreatic, breast, and lung cancers. The drug is primarily being studied in early-phase clinical trials and compassionate use settings to evaluate its safety, dosimetry, and efficacy in treating metastatic solid malignancies.

Other names

Actinium-225 fibroblast activation protein inhibitor XTActinium225 fibroblast activation protein inhibitor XTActinium 225 fibroblast activation protein inhibitor XT[225Ac]Ac-FAPI-XTFAP-i-XT