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.

NCX-4016, a nitric oxide non-steroidal anti-inflammatory drug (NO-NSAID) which can inhibit cyclooxygenase as well as release nitric oxide, is under development by NicOx as a potential treatment for thrombosis, inflammation and rheumatoid arthritis. NCX-4016 possesses a broad spectrum of antithrombotic and antiinflammatory activities. NCX-4016 has been shown to inhibit platelet activation in vitro more effectively than aspirin, to inhibit smooth muscle cell proliferation, to exert an endothelial cell protective activity and to suppress the function of several inflammatory cells potentially involved in atherothrombosis. In animal models, NCX-4016 protected from platelet thromboembolism, prevented restenosis in atherosclerosis-prone animals, protected the heart from ischemia/reperfusion injury, and induced neoangiogenesis in critically ischemic limbs. Moreover, it displayed little or no gastric toxicity and appeared to protect stomach from noxious stimuli, including aspirin. NCX-4016 has been evaluated in healthy volunteers and found to inhibit platelet cyclo-oxygenase-1 (COX-1) similarly to or slightly less than aspirin, to raise the circulating levels of NO-degradation products, and to have little or no gastric toxicity in short term studies. NCX-4016 was in Phase II clinical trials for the treatment of vascular disorders such as peripheral vascular disease and other cardiovascular diseases including thrombosis, complications of endothelium-related diseases such as diabetes and other. But this research was discontinued.

MK-571 is a selective, orally active leukotriene D4/E4 (LTD4/E4) receptor antagonist patented by Merck Frosst Canada, Inc. for the treatment bronchoconstriction. In ex vivo models MK-571 competitively antagonizes contractions of guinea pig trachea and ileum induced by leukotriene (LT) D4 and LTE4 and contractions of human trachea induced by LTD4. MK-571 antagonizes bronchoconstriction induced in anesthetized guinea pigs by i.v. LTC4, LTD4, and LTE4 but do not block bronchoconstriction to arachidonic acid. In clinical trials, MK-571 is a potent antagonist of LTD4-induced bronchoconstriction in both normal volunteers and asthmatic patients.