Abstract
Targeting the prostate-specific membrane antigen (PSMA) with radiopharmaceuticals for imaging and/or therapy has demonstrated significant advancement in the management of prostate cancer patients. However, PSMA targeting remains unsuccessful in prostate cancers with low expression of PSMA, which account for 15% of cases. The neurotensin receptor-1 (NTS1) has been highlighted as a suitable oncotarget for imaging and therapy of PSMA-negative prostate cancer lesions. Therefore, heterobivalent probes targeting both PSMA and NTS1 could improve the prostate cancer management. Herein, we report the development of a branched hybrid probe (JMV 7489) designed to target PSMA and/or NTS1 bearing relevant pharmacophores and DOTA as the chelating agent. The new ligand was synthesized with a hybrid approach, which includes both syntheses in batch and in the solid phase. Saturation binding experiments were next performed on HT-29 and PC3-PIP cells to derive Kd and Bmax values. On the PC3-PIP cells, [68Ga]Ga-JMV 7489 displayed good affinity towards PSMA (Kd = 53 ± 17 nM; Bmax = 1393 ± 29 fmol/106 cells) in the same range as the corresponding reference monomer. A lower affinity value towards NTS1 was depicted (Kd = 157 ± 71 nM; Bmax = 241 ± 42 fmol/106 cells on PC3-PIP cells; Kd = 246 ± 1 nM; Bmax = 151 ± 44 fmol/106 cells on HT-29 cells) and, surprisingly, it was also the case for the corresponding monomer [68Ga]Ga-JMV 7089. These results indicate that the DOTA macrocycle and the linker are critical elements to design heterobivalent probes targeting PSMA and NTS1 with high affinity towards NTS1.