Our results suggest that potent, small-molecule inhibitors of PSMA can be utilized as carriers for targeted delivery for prostate cancer for future imaging and therapeutic applications.

The mode of inhibition for phosphoramidate peptidomimetic inhibitors of prostate-specific membrane antigen was determined by inhibition reversibility experiments. The results revealed that these inhibitors can be classified into three types: pseudoirreversible (compounds 1-3), moderately reversible (compounds 4-9), and rapidly reversible inhibitors (compounds 10 and 11). Representative compounds from each class were further evaluated for their ability to induce cellular internalization of PSMA. Results from these experiments revealed that the pseudoirreversible inhibitor 1 induced the greatest PSMA internalization. The discovery of pseudoirreversible PSMA inhibitors is expected to provide a new avenue of investigation and therapeutic applications for prostate cancer and neurological disorders.

To identify the pharmacophore of a phosphoramidate peptidomimetic inhibitor of prostate-specific membrane antigen (PSMA), a small analog library was designed and screened for inhibitory potency against PSMA. The design of the lead inhibitor was based upon N-acyl derivatives of endogenous substrate folyl-gamma-Glu and incorporates a phosphoramidate group to interact with the PSMA catalytic zinc atoms. The scope of the analog library was designed to test the importance of various functional groups to the inhibitory potency of the lead phosphoramidate. The IC(50) for the lead phosphoramidate inhibitor was 35 nM while the IC(50) values for the analog library presented a range from 0.86 nM to 4.1 microM. Computational docking, utilizing a recently solved X-ray crystal structure of the recombinant protein, along with enzyme inhibition data, was used to propose a pharmacophore model for the PSMA active site.

Prostate-specific membrane antigen (PSMA) is a membrane-bound cell surface peptidase which is over-expressed in prostate cancer cells. The enzymatic activities of PSMA are understood but the role of the enzyme in prostate cancer remains conjectural. We previously confirmed the existence of a hydrophobic binding site remote from the enzyme's catalytic center. To explore the specificity and accommodation of this binding site, we prepared a series of six glutamate-containing phosphoramidate derivatives of various hydroxysteroids (1a-1f). The inhibitory potencies of the individual compounds of the series were comparable to a simple phenylalkyl analog (8), and in all cases IC 50 values were sub-micromolar. Molecular docking was used to develop a binding model for these inhibitors and to understand their relative inhibitory potencies against PSMA.A notable discovery in prostate cancer research has been the identification of an over-expressed membrane-bound cell surface protein on prostate cancer cells, namely, prostate-specific membrane antigen (PSMA). PSMA, also known as folate hydrolase I (FOLH1) and glutamate carboxypeptidase II (GCPII), 1-3 is a 750-amino acid type II membrane glycoprotein 4 and was discovered during the development of the LNCaP cell line; one which retains most of the known features of prostate cancer. 5Although PSMA is primarily expressed in normal human prostate epithelium, the importance of this enzyme lies with the fact that it is upregulated and strongly expressed in prostate cancer cells, including those of the metastatic disease state. 6 It has also been demonstrated PSMA expression is present in the endothelium of tumor-associated neovasculature of multiple nonprostatic solid malignancies, 7 including metastatic renal carcinoma. 8 As such, it is not surprising that PSMA has attracted a great deal of attention as a target for immunotherapy. 9-12 In addition to its immunological importance, PSMA is also reported to possess two predominant, yet poorly understood enzymatic activities: the hydrolytic cleavage and liberation of glutamate from γ-glutamyl derivatives of folic acid 13, 14 and the proteolysis of the neuropeptide N-acetylaspartylglutamate (NAAG) 2 . With respect to its function, recent studies suggest that PSMA plays a regulatory role in angiogenesis. 15Recently, we identified the presence of a hydrophobic binding site remote from the catalytic center of PSMA using a series of phenylalkylphosphonamidate derivatives of glutamic acid. 16 Based upon ongoing substrate and inhibitor-based studies in our lab, we have determined that PSMA can accommodate a variety of structural motifs remote from the catalytic center.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production ...

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