Selective Small Molecule Inhibitors of 12-Human Lipoxygenase (12-hLO)

Human lipoxygenases (hLOs) are distributed among a variety of tissues and cellular locations in the body, and they are part of the first committed step in a cascade of metabolic pathways. As such, hLOs are implicated in the onset of inflammatory diseases such as cancers, heart disease and asthmas, making them an ideal target for pharmaceutical intervention. The lipoxygenase platelet-type 12-()-hLO has been implicated in skin diseases, diabetes, platelet hemostasis, thrombosis and cancer. Despite the potential of 12-hLO as a therapeutic target, potent and selective inhibitors of the enzyme are lacking in the patent or public literature. To date, the only known modulators of 12-hLO are either weak inhibitors or promiscuous polyphenolic compounds that inhibit several of the closely related isoymes. In this report, we describe the development of small-molecule inhibitors that exhibit nanomolar potency against 12-hLO and >50-fold selectivity over the related lipoxygenases and cyclooxygneases. Kinetic experiments indicate that this chemotype is a non-competitive inhibitor that does not reduce the active site iron. Moreover, chiral HPLC separation of several of the racemic lead molecules revealed a strong preference for the (−)-enantiomer (IC ~ 0.4μM) compared to > 25μM for the (+)-enantiomer, indicating a fine degree of selectivity in the active site due to chiral geometry. The small molecule probe ML127 (CID-44460175) and its related analogs represent the most potent and selective 12-hLO inhibitors reported thus far.