FAPI-X5 is a fibroblast activation protein (FAP) inhibitor. FAPI-X5 binds to the FAP catalytic domain, forming hydrogen bonds with key active residues and engaging in π-π stacking to drive functional inhibition. FAPI-X5 exhibits albumin binding activity to prolong systemic circulation half-life. FAPI-X5 induces cytostatic effects on glioblastoma tumors, slowing tumor growth without regression. FAPI-X5, when labeled with 68Ga, acts as a PET tracer with rapid tumor uptake and high-contrast imaging in glioblastoma tumor-bearing mice. FAPI-X5, when labeled with 177Lu or 47Sc, functions as a targeted radionuclide agent with prolonged tumor retention. FAPI-X5 can be used for the research of glioblastoma.
