L-699333

L-699333 is a 5-lipoxygenase (5-LO) inhibitor belonging to the thieno[2,3,4-cd]indole class. This compound has a 2-ethoxybutyric acid side chain and is a potent inhibitor of the biosynthesis of 5-HPETE and LTB4 produced from human 5-LO, with ICm values of 22 nM, 7 nM, and 3.8 pM for human neutrophils and whole blood, respectively. L-699333 has shown anti-inflammatory and antiasthmatic effects in a variety of animal models, including rat pleurisy models, antigen-induced wheezing models, and awake macaque and sheep asthma models. Its inhibition of 5-LO is highly selective, with higher ICm values or stronger competitive inhibition in FLAP binding assays compared to inhibition of human 15-LO, porcine 12-LO, and ram epididymal cyclooxygenase. The racemic enantiomer 14g of L-699333 is the most potent enantiomer to date, with inhibitory effects similar to those of the known MK-0591, which has been shown in clinical trials to inhibit the biochemical effects of LTB4 biosynthesis in vitro and LTE4 excretion in urine.