Vipivotide tetraxetan

Vipivotide tetraxetan (PSMA-617) is a high potent prostate-specific membrane antigen (PSMA) inhibitor, with a K_i of 0.37 nM. Vipivotide tetraxetan (PSMA-617) is designed consisting of three components: the pharmacophore Glutamate-urea-Lysine, the chelator DOTA able to complex both 68Ga or 177Lu, and a linker connecting these two entities. Glutamate-urea-Lysine is the selective pharmacophore to bind to prostate specific membrane antigen. IC50 & Target:Ki: 0.37 nM (PSMA)^[1]. In Vitro: Vipivotide tetraxetan (PSMA-617) demonstrates high radiolytic stability for at least 72 h. A high inhibition potency (equilibrium dissociation constant K_i=2.34±2.94 nM on LNCaP; K_i=0.37±0.21 nM enzymatically determined) and highly efficient internalization into LNCaP cells are demonstrated^[1]. In Vivo: Organ distribution with 68Ga-labeled Vipivotide tetraxetan (PSMA-617) after 1 h (n=3) reveals a high specific uptake in LNCaP tumors and in the kidneys. The high uptake in the kidneys is nearly completely blocked by coinjection of 2 mg of 2-PMPA per kilogram. Other organs such as the liver, lung, and spleen show rather low uptake and no blocking effect, with the exception of the spleen. Tumor-to-background ratios are 7.8 (tumor to blood) and 17.1 (tumor to muscle) at 1 h after injection. As compared with the 68Ga-labeled version, the organ distribution with 177Lu-labeled Vipivotide tetraxetan (PSMA-617) (n=3) show a similar uptake in the LNCaP tumors and in the kidneys. The liver uptake is found to be statistically different. Tumor-to-background ratios determined 1 h after injection show slightly higher values (tumor to blood, 22.1; tumor to muscle, 25.6) than previous organ distribution with 68Ga-labeled Vipivotide tetraxetan (PSMA-617)^[1].