Recent advances in the discovery and development of glyoxalase I inhibitors.

Glyoxalase I (GLO1) is a homodimeric Zn2+-metalloenzyme that catalyses the transformation of methylglyoxal (MG) to d-lacate through the intermediate S-d-lactoylglutathione. Growing evidence indicates that GLO1 has been identified as a potential target for the treatment cancer and other diseases. Various inhibitors of GLO1 have been discovered or developed over the past several decades including natural or natural product-based inhibitors, GSH-based inhibitors, non-GSH-based inhibitors, etc. The aim of this review is to summarize recent achievements of concerning discovery, design strategies, as well as pharmacological aspects of GLO1 inhibitors with the target of promoting their development toward clinical application.

Design, Synthesis and Biological Evaluation of Potent Human Glyoxalase I Inhibitors.

Several glutathione derivatives bearing the S-(N-aryl-N-hydroxycarbamoyl) or S-(C-aryl-N-hydroxycarbamoyl) moieties (10, 10', 13-15) were synthesized, characterized, and their human glyoxalase I (hGLO1) inhibitory activity was evaluated. Compound 10 was proved to be the effective hGLO1 inhibitor with a Ki value of 1.0 nM and the inhibition effect of compound 10 on hGLO1 was nearly ten-fold higher than that of the strongest inhibitor 2 (Ki=10.0 nM) which has been reported in the field of glutathione-type hGLO1 inhibitors. Its diethyl ester prodrug 10' was able to penetrate cell membrane and had good inhibitory effect on the growth of NCI-H522 cell xenograft tumor model.

Novel bivalent inhibitors with sub-nanomolar affinities towards human glyoxalase I.

The zinc metalloenzyme glyoxalase I (GlxI) catalyzes the glutathione-dependent inactivation of cytotoxic methylglyoxal. Two competitive bivalent GlxI inhibitors, polyBHG2-62 (Ki=1.0 nM) and polyBHG2-54 (Ki=0.3 nM), were synthesized based on the transition-state analog S-(N-bromophenyl-N-hydroxycarbamoyl) glutathione (BHG). The most effective inhibitor, polyBHG2-54, is the first subnanomolar inhibitor of GlxI, and is over 50-fold more potent than BHG itself.

Bivalent transition-state analogue inhibitors of human glyoxalase I.

A new class of competitive inhibitors of homodimeric human glyoxalase I has been created by cross-linking two molecules of the transition-state analogue S-(N-4-chlorophenyl-N-hydroxycarbamoyl)glutathione (CHG) through their gamma-glutamyl-NH(2) groups with poly-beta-alanyl tethers of differing length: [CHG(beta-ala)n](2) suberate diamide (n = 1-7). The strongest inhibitors of this antitumor target enzyme likely bind simultaneously to the active site on each subunit to give K(i) values as small as 0.96 nM (n = 6). [structure: see text]

N-(2-hydroxypropyl)methacrylamide copolymers of a glutathione (GSH)-activated glyoxalase i inhibitor and DNA alkylating agent: synthesis, reaction kinetics with GSH, and in vitro antitumor activities.

The incorporation of anticancer prodrugs into polyacrylamide conjugates has been shown to improve tumor targeting via the so-called "enhanced permeability and retention" effect. This strategy has now been expanded to include two different classes of glutathione (GSH)-activated antitumor agents prepared by radical polymerization of N-(2-hydroxypropyl)methacrylamide (HPMA) with 2-methacryloyloxy-methyl-2-cyclohexenone (7) and/or with S-(N-4-chlorophenyl-N-hydroxycarbamoyl-thioethyl)methacrylamide (8), followed by treatment with 3-chloroperoxybenzoic acid, to give the HPMA copolymers of 7 and the 8-sulfoxide, respectively. In aqueous-buffered solution at pH 6.5, GSH reacts rapidly with poly-HPMA-8-sulfoxide (k approximately 2.3 mM(-1) min(-1)) to give S-(N-4-chlorophenyl-N-hydroxycarbamoyl)glutathione (1), a tight-binding transition state analogue inhibitor of the antitumor target enzyme glyoxalase I (K(i) = 46 nM), or with poly-HPMA-7 (k approximately 0.02 mM(-1) min(-1)) to give the electrophilic antitumor agent 3-glutathio-2-methylenecyclohexenone (4). Indeed, B16 melanotic melanoma in culture is inhibited by poly-HPMA-8-sulfoxide and by poly-HPMA-7 with IC(50) values of 168 +/- 8 and 284 +/- 5 microM, respectively. These values are significantly greater than those of the unpolymerized prodrugs suggesting that the cytotoxicity of the polymer prodrugs might be limited by slow cellular uptake via pinocytosis. This prodrug strategy should be applicable to a range of different GSH-based antitumor agents.