CMI977 is a potent 5-Lipoxygenase (5-LO) inhibitor. In Vitro: CMI977 is a potent 5-lipoxygenase (5-LO) inhibitor that intervenes in the production of leukotrienes and is presently being developed for the treatment of chronic asthma. It is a single enantiomer with an all-trans (2S,5S) configuration. Of the four isomers of CMI977, the S,S isomer is found to have the best biological activity and is selected for further development.