Acebilustat (formerly CTX-4430) is an investigational oral drug under development by Celtaxsys. It is a potent inhibitor of the enzyme leukotriene A4 hydrolase (LTA4H), which catalyzes the rate‐limiting step in the formation of leukotriene B4 (LTB4), a potent chemoattractant and activator of inflammatory immune cells including neutrophils. Acebilustat is currently being tested in Phase 2 clinical trial as a modulator of inflammation in patients with cystic fibrosis (CF). The U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have granted orphan drug status to acebilustat as a treatment for cystic fibrosis.