ABSTRACT
By incorporating an N-hydroxyurea functionality onto diaryltetrahydrofurans, a novel series of compounds was investigated as dual 5-lipoxygenese (5-LO) inhibitor and platelet-activating factor (PAF) receptor antagonist. These dual functional compounds were evaluated in vitro for 5-LO inhibition in RBL cell extracts and human whole blood, and PAF receptor antagonism in a receptor binding assay. PAF-induced hemoconcentration and arachidonic acid- and TPA-induced ear edema in mice were used to determine in vivo activities. The structure-activity relationship analysis to define a preclinical lead is presented. (+/-)-trans-2-[3-methoxy-4-(4-chlorophenylthioethoxy)-5-(N-methyl- N-h ydroxyureidyl)methylphenyl]-5-(3,4, 5-trimethoxyphenyl)tetrahydrofuran (40, CMI-392) was selected for further study. In the arachidonic acid-induced mouse ear edema model, 40 was more potent than either zileuton (a 5-LO inhibitor) or BN 50739 (a PAF receptor antagonist), and it demonstrated the same inhibitory effect as a physical combination of the latter two agents. These results suggest that a single compound which both inhibits leukotriene synthesis and blocks PAF receptor binding may provide therapeutic advantages over single-acting agents. The clinical development of compound 40 is in progress.
Subject(s)
Enzyme Inhibitors/pharmacology , Furans/pharmacology , Lipoxygenase Inhibitors , Platelet Membrane Glycoproteins/antagonists & inhibitors , Receptors, Cell Surface , Receptors, G-Protein-Coupled , Urea/analogs & derivatives , Animals , Arachidonic Acid/toxicity , Blood Platelets/drug effects , Blood Platelets/metabolism , Blood Platelets/ultrastructure , CHO Cells , Cell Membrane/drug effects , Cell Membrane/metabolism , Cricetinae , Drug Evaluation, Preclinical , Edema/chemically induced , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Furans/chemical synthesis , Furans/chemistry , Hematocrit , Humans , Leukotriene B4/biosynthesis , Leukotriene B4/blood , Mice , Rats , Structure-Activity Relationship , Tetradecanoylphorbol Acetate/toxicity , Tumor Cells, Cultured , Urea/chemical synthesis , Urea/chemistry , Urea/pharmacologyABSTRACT
The high intracellular level of glutathione is maintained, in part, by the important redox enzyme glutathione reductase. This report describes the properties of a new inhibitor of glutathione reductase, 2,4-dihydroxybenzylamine (2,4-DHBA). The inhibition of glutathione reductase by both 2,4-DHBA and 1,3-bischloroethyl-nitrosourea (BCNU) requires the presence of the co-factor NADPH. However, the inhibition caused by 2,4-DHBA was found to occur much more rapidly. Inhibition of glutathione reductase was time dependent, involved a stoichiometric titration of the enzyme, and was not reversed by gel-filtration indicating an irreversible inhibitory mechanism. The drug interacted at two inhibitory sites as determined by a Hill-type plot analysis. 2,4-DHBA was shown to compete with the substrate oxidized glutathione, and the reducing agents, glutathione and dithioerythritol, were found to protect the enzyme from its inhibitory effect. These results suggest that the inhibition may entail a free radical effect at or near the active site. A structure-activity analysis with other meta-dihydroxybenzene derivatives revealed that the inhibition of glutathione reductase was unique to 2,4-dihydroxybenzylamine.
