Iralukast is a cysteinyl-leukotriene antagonist (CysLT) with a pKi of 7.8 for CysLT1.
Both Iralukast and CGP 57698 are able to compete for the two sites labelled by [3H]-LTD4. As in all the G-protein coupled receptors, Iralukast and CGP 57698 do not discriminate between the high and the low affinitystates of the CysLT receptor labelled by LTD4 (Ki1=Ki2=16.6 nM±36% CV and Ki1=Ki2=5.7 nM±19% CV, respectively). Iralukast, displays a slow bindingkinetic, because preincubation (15 min) increases its antagonist potency. Iralukast and CGP 57698 antagonize LTD4-induced contraction of humanbronchi, with pA2 values of 7.77±4.3% CV and 8.51±1.6% CV, respectively, and slopes not significantly different from unity[2].
[1]. Magnus B?ck, et al. Update on leukotriene, lipoxin and oxoeicosanoid receptors: IUPHAR Review 7. Br J Pharmacol. 2014 Aug; 171(15): 3551-3574. [2]. Valérie Capra, et al. Pharmacological characterization of the cysteinyl-leukotrieneantagonists CGP 45715A (iralukast) and CGP 57698 in human airways in vitro.Br J Pharmacol. 1998 Feb; 123(3): 590-598.