Rational design of NT-PSMA heterobivalent probes for prostate cancer theranostics

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 K_d and B_max values. On the PC3-PIP cells, [⁶⁸Ga]Ga-JMV 7489 displayed good affinity towards PSMA (K_d = 53 ± 17 nM; B_max = 1393 ± 29 fmol/10⁶ cells) in the same range as the corresponding reference monomer. A lower affinity value towards NTS₁ was depicted (K_d = 157 ± 71 nM; B_max = 241 ± 42 fmol/10⁶ cells on PC3-PIP cells; K_d = 246 ± 1 nM; B_max = 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.