(R)-(+)-N-[3-[5-[(4-fluorophenyl)methyl]-2-thienyl]-1-methyl- 2-propynyl]-N-hydroxyurea (ABT-761), a second-generation 5-lipoxygenase inhibitor

Structure-activity optimization of inhibitory potency and duration of action of N-hydroxyurea containing 5-lipoxygenase inhibitors was conducted. The lipophilic heteroaryl template and the link group connecting the template to the N-hydroxyurea pharmacophore were modified. Inhibition of 5-lipoxygenase was evaluated in vitro in a human whole blood assay. An in vitro assay using liver microsomes from monkey was used to evaluate congeners for comparative rates of glucuronidation. (3-Heteroaryl-1-methyl-2-propynyl)-N-hydroxyureas were found to be more resistant to in vitro glucuronidation. The promising inhibitor N-[3-[5-(4-fluorophenoxy)-2-furyl]-1-methyl-2-propynyl]-N- hydroxyurea (6) was found to have stereoselective glucuronidation in monkey and man. The R enantiomer 7 provided longer duration of inhibition as evaluated by an ex vivo whole blood assay. Further optimization of the lipophilic template led to the discovery of (R)-(+)-N-[3-[5-[(4-fluorophenyl)methyl]-2- thienyl]-1-methyl-2-propynyl]-N-hydroxyurea (11) with more effective and prolonged inhibition of leukotriene biosynthesis than zileuton (1) and 7 in monkey and man. The optimized 5-lipoxygenase inhibitor 11 was selected for development as an investigational drug for leukotriene-mediated disorders.