4-[5-Fluoro-3-[4-(2-methyl-1<i>H</i>-imidazol-1-yl)benzyloxy]phenyl]-3,4,5,6- tetrahydro-2<i>H</i>-pyran-4-carboxamide, an Orally Active Inhibitor of 5-Lipoxygenase with Improved Pharmacokinetic and Toxicology Characteristics

Abstract

Described herein are structure-activity relationships (SARs) of 4-[5-fluoro-3-[4-(2-methyl-1H-imidazol-1-yl)benzyloxy]-phenyl]-4-methoxy-3,4,5,6-tetrahydro-2H-pyran (1, CJ-12,918), an imidazole 5-lipoxygenase (5-LO) inhibitor. When 1 was tested in preclinical studies, cataract formation was observed in rats; however, this compound was metabolized extensively in vivo and showed low systemic exposure. To eliminate this side effect and enhance bioavailability, structural modification was focused on replacing the methoxy group of 1 by modulating lipophilicity (i.e., predicted log D at pH 7.4). The SARs led to the discovery of 4-[5-fluoro-3-[4-(2-methyl-1H-imidazol-1-yl)benzyloxy]phenyl]-3,4,5,6-tetrahydro-2H-pyran-4-carboxamide (10, CJ-13,454), which was less lipophilic by 1.2 log D units and showed in vivo potency (ED(50) = 4-9 mg/kg) equipotent to 1. Enhanced metabolic stability resulted in fewer in vivo metabolites, as well as improved bioavailability and a better toxicological profile. Thus, 10 was found to be a more practical lead for an orally active 5-LO inhibitor.