PSMA-D4 Radioligand for Targeted Therapy of Prostate Cancer: Synthesis, Characteristics and Preliminary Assessment of Biological Properties

Abstract

A new PSMA ligand (PSMA-D4) containing the Glu-CO-Lys pharmacophore connected with a new linker system (L-Trp-4-Amc) and chelator DOTA was developed for radiolabeling with therapeutic radionuclides. Herein we describe the synthesis, radiolabeling, and preliminary biological evaluation of the novel PSMA-D4 ligand. Synthesized PSMA-D4 was characterized using TOF-ESI-MS, NMR, and HPLC methods. The novel compound was subject to molecular modeling with GCP-II to compare its binding mode to analogous reference compounds. The radiolabeling efficiency of PSMA-D4 with 177Lu, 90Y, 47Sc, and 225Ac was chromatographically tested. In vitro studies were carried out in PSMA-positive LNCaP tumor cells membranes. The ex vivo tissue distribution profile of the radioligands and Cerenkov luminescence imaging (CLI) was studied in LNCaP tumor-bearing mice. PSMA-D4 was synthesized in 24% yield and purity >97%. The radio complexes were obtained with high yields (>97%) and molar activity ranging from 0.11 to 17.2 GBq mcmol−1, depending on the radionuclide. In vitro assays confirmed high specific binding and affinity for all radiocomplexes. Biodistribution and imaging studies revealed high accumulation in LNCaP tumor xenografts and rapid clearance of radiocomplexes from blood and non-target tissues. These render PSMA-D4 a promising ligand for targeted therapy of prostate cancer (PCa) metastases.

More Than Meets the Eye: Scientific Rationale behind Molecular Imaging and Therapeutic Targeting of Prostate-Specific Membrane Antigen (PSMA) in Metastatic Prostate Cancer and Beyond

“…Additionally, several small-molecule ligand and antibody alternatives to PSMA-617 and PSMA-I&T are being tested ( Table 1 ). Moreover, other promising ligands and radionuclides that show potential to attain greater efficacy are being presented or already have entered clinical trials [ 104 , 105 , 106 ]. A randomized phase II open-label study ( Table 1 , NCT03939689) is investigating a radioconjugate 131 I-1095, for delivering iodine cytotoxicity selectively to the PSMA-expressing prostate cancer cells, in combination with enzalutamide in patients with mCRPC.…”

Synthesis, Characterization, and Preclinical Evaluation of a Small-Molecule Prostate-Specific Membrane Antigen-Targeted Monomethyl Auristatin E Conjugate

“…This conjugate is capable of chelating the isotopes 90 Y, 47 Sc, 68 Ga, and 177 Lu. 25 Its derivative PSMA-T4, where a fragment of DOTA is replaced with a fragment of HYNIC, is also known to bind 99m Tc isotopes. 26,27 However, right now 68 Ga-PSMA-11, which was recently approved by the FDA, is the most interesting.…”

“…Also among the promising radiopharmaceuticals is a recently proposed analog of PSMA-617, a PSMA-D4 conjugate where the 2-naphthylalanine fragment is replaced by tryptophan. This conjugate is capable of chelating the isotopes 90 Y, 47 Sc, 68 Ga, and 177 Lu . Its derivative PSMA-T4, where a fragment of DOTA is replaced with a fragment of HYNIC, is also known to bind 99m Tc isotopes. , However, right now 68 Ga-PSMA-11, which was recently approved by the FDA, is the most interesting .…”

The Evolving Coordination Chemistry of Radiometals for Targeted Alpha Therapy

“…[14] [ 225 Ac][Ac(DOTA)]administered intravenously to adult C57BL/6 mice cleared rapidly via the urine, demonstrating that the complex is stable in vivo for at least 5 h. [14,40] Several constructs using [ 225 Ac] [Ac(DOTA)]have subsequently been produced featuring targeting groups, including small molecules, peptides, and antibodies. [21,[24][25][26][27][28][29][30][31]39,[41][42][43][44][45][46][47] Initial studies to prepare [ 225 Ac][AcDOTA] --antibody constructs utilised a two-step procedure that involved radiolabelling the bifunctional p-SCN-Bn-H 4 DOTA (Bn ¼ benzyl) chelator with 225 Ac 3þ at 55-608C before attachment to temperaturesensitive antibodies. [48] This process was utilised successfully to prepare the anti-prostate specific membrane antigen (PSMA) construct [ 225 Ac][Ac(DOTA-J591)] -, which was readily internalised by cancer cells and led to tumour regression and prolonged survival of mice bearing prostate carcinoma.…”

“…Acyclic picolinates H 4 neunpa [20,21] N 5 O 4 RT, 1 h, pH 5.5, 10 À3 M G H 4 phospa [21] N 4 O 4 77 D RT, 1 h, pH 5.5, 10 À3 M H 4 noneunpa [20] N 4 O 5 90 D RT, 1 h, pH 5.5, 10 À6 M H 4 octapa [21] N 4 O 4 20.13 93 D RT, 1 h, pH 5.5, 10 À5 M H 4 CHXoctapa [21] PSMA; [25][26][27][28][29][30] tetrazine-TCO [31] H 4 DOTP [24] N 4 O 4 Capped inverted square prism 408C, 30 min, pH 10, 10 À2 M 18-Crown-6-based H 2 macropa [32,33] N 4 O 6 Irregular tridecahedron 14.99 99 E RT, 5 min, pH 6, 10 À7 M PSMA; [14,34] trastuzumab [14] H 4 crown N 4 O 6 90 RT, 10 min, pH 5-7, 10 À6 M aMSH [35] A From the La 3þ X-ray crystallographic structure.…”