Glutamate carboxypeptidase II (GCPII), also known as prostate specific membrane antigen (PSMA), is an established prostate cancer marker and is considered a promising target for specific anticancer drug delivery. Low-molecular-weight inhibitors of GCPII are advantageous specific ligands for this purpose. However, they must be modified with a linker to enable connection of the ligand with an imaging molecule, anticancer drug, and/or nanocarrier. Here, we describe a structure-activity relationship (SAR) study of GCPII inhibitors with linkers suitable for imaging and drug delivery. Structure-assisted inhibitor design and targeting of a specific GCPII exosite resulted in a 7-fold improvement in Ki value compared to the parent structure. X-ray structural analysis of the inhibitor series led to the identification of several inhibitor binding modes. We also optimized the length of the inhibitor linker for effective attachment to a biotin-binding molecule and showed that the optimized inhibitor could be used to target nanoparticles to cells expressing GCPII.
Keywords: GCPII; PSMA; Specific drug targeting; Structure-aided drug design.
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