A two-fold lower tumor accumulation compared to [177Lu]Lu-1 already 1 h p.i. (5.31 ± 0.94% ID/g) in combination with a rapid decline to 1.20 ± 0.55% ID/g at 24 h p.i., led to the assumption that in vivo decomposition of the inhibitor motif might have generated a non-PSMA-binding ligand, resulting in fast renal excretion (0.31 ± 0.05% ID/g for [177Lu]Lu-3 vs. 1.97 ± 0.78% ID/g for [177Lu]Lu-1, 24 h p.i.). This evidence concerns the gene PDZD4 and neoplasm.