With a maximum tumor accumulation of 0.33 ± 0.11% ID/g for [177Lu]Lu-6 (proinhibitor II) and a minimum tumor accumulation of 0.09 ± 0.02% ID/g for [177Lu]Lu-5 (proinhibitor I), all investigated proinhibitors showed very low ability to bind to PSMA-expressing tumors (24 h p.i.), as depicted in Fig. 3. Here, FOLH1 is linked to neoplasm.