First report on 3D-QSAR and molecular dynamics based docking studies of GCPII inhibitors for targeted drug delivery applications

Imaging of prostate cancer: optimizing affinity to prostate specific membrane antigen by spacer modifications in a tumor spheroid model

Early diagnosis of prostate cancer (PCa) is crucial for staging, treatment and management of patients. Prostate specific membrane antigen (PSMA), highly over-expressed on PCa cells, is an excellent target for selective imaging of PCa. In recent years, various scaffolds have been explored as potential carriers to target diagnostic and therapeutic agents to PSMA⁺ tumour cells. Numerous fluorescent or radioisotope probes linked via a peptide linker have been developed that selectively binds to PCa cells. However, there are very few reports that examine the effects of chemical modifications in the peptide linker of an imaging probe on its affinity to PSMA protein. This report systematically investigates the impact of hydrophobic aromatic moieties in the peptide linker on PSMA affinity and in vitro performance. For this, a series of fluorescent bioconjugates 12-17 with different aromatic spacers were designed, synthesized, and their interactions within the PSMA pocket were first analysed in silico. Cell uptake studies were then performed for 12-17 in PSMA⁺ cell lines and 3D tumour models in vitro. Binding affinity values of 12-17 were found to be in the range of 36 to 157.9 nM, and 12 with three aromatic groups in the spacer exhibit highest affinity (K_D = 36 nM) compared to 17 which is devoid of aromatic groups. These studies suggest that aromatic groups in the spacer region can significantly affect deep tissue imaging of fluorescent bioconjugates. Bioconjugate 12 can be a promising diagnostic tool, and conjugation to near-infrared agents would further its applications in deep-tissue imaging and surgery. Communicated by Ramaswamy H. Sarma.

Metamorphosis of prostate specific membrane antigen (PSMA) inhibitors

Prostate-specific membrane antigen (PSMA), also called glutamate carboxypeptidase II (GCP(II)), is a Zn-dependent metalloprotease that is known as a well prostate cancer indication and a potential targeting towards anti-cancer medicines and drug delivery. Because of its centrality in the diagnostics and treatment of prostate cancer, several types of inhibitors are designed with particular scaffolds. In this study, important groups of related inhibitors as well as reported experimental and computational studies are being reviewed, in which we examined three functional groups on each group of structures. The importance of computational biochemistry and the necessity of extensive research in this area on PSMA and its effective ligands are recommended.

Interactions of Urea-Based Inhibitors with Prostate-Specific Membrane Antigen for Boron Neutron Capture Therapy

In this study, molecular interactions of prostate-specific membrane antigen (PSMA) with five chemically distinct urea-based boron-containing inhibitors have been investigated at the atomic level using molecular docking and molecular dynamics simulations. The PSMA-inhibitor complexations have been analyzed by comparing their binding modes, secondary structures, root-mean-square deviations, noncovalent interactions, principal components, and binding free energies. PSMA is a cell surface glycoprotein upregulated in cancerous cells and can be targeted by boron-labeled inhibitors for boron neutron capture therapy (BNCT). The effective BNCT requires the selective boron delivery to the tumor area and highly specific PSMA-mediated cellular uptake by tumor. Thus, a potent inhibitor must exhibit both high binding affinity and high boron density. The computational results suggest that the chemical nature of inhibitors affects the binding mode and their association with PSMA is primarily dominated by hydrogen bonding, salt bridge, electrostatic, and π-π interactions. The binding free energies (-28.0, -15.2, -43.9, -23.2, and -38.2 kcal/mol) calculated using λ-dynamics for all inhibitors (In1-5) predict preferential binding that is in accordance with experimental data. Among all inhibitors, In5 was found to be the best candidate for BNCT. The binding of this inhibitor to PSMA preserved its overall secondary structure. These results provide computational insights into the coordination flexibility of PSMA and its interaction with various inhibitors. They can be used for the design and synthesis of efficient BNCT agents with improved drug selectivity and high boron percentage.