Radiopharmaceutical Peptide
A peptide conjugated to a radioactive isotope for imaging or therapy. Lutetium Lu-177 dotatate targets somatostatin receptor-positive neuroendocrine tumours, and lutetium Lu-177 vipivotide tetraxetan targets PSMA-expressing prostate cancer. This approach is called peptide receptor radionuclide therapy (PRRT).
Technical Context
Peptide receptor radionuclide therapy (PRRT) concept: a tumour-targeting peptide (delivering specificity) is conjugated via a chelator (DOTA, DTPA) to a therapeutic radionuclide (delivering cytotoxicity). Lutetium-177 (Lu-177): beta-emitter, half-life 6.7 days, tissue penetration 0.25-2mm, suitable for small-to-medium tumour deposits. Yttrium-90 (Y-90): beta-emitter, half-life 2.7 days, tissue penetration up to 11mm, suitable for larger tumours. Lu-177 dotatate (Lutathera): DOTA-Tyr3-octreotate chelated to Lu-177, targeting SSTR2-positive NETs. The NETTER-1 Phase III trial showed significant PFS benefit vs high-dose octreotide LAR. Lu-177 vipivotide tetraxetan (Pluvicto): targets PSMA on prostate cancer cells. Selection requires diagnostic imaging with Ga-68 DOTATATE PET (for NETs) or Ga-68 PSMA PET (for prostate cancer) to confirm target expression — a theranostic approach (diagnosis and therapy using the same peptide targeting moiety with different radionuclides).