Pharmacological characterization of the first potent and selective antagonist at the cysteinyl leukotriene 2 (CysLT2) receptor

Background and purpose: Cysteinyl leukotrienes (CysLTs) have been implicated in the pathophysiology of inflammatory and cardiovascular disorders. Their actions are mediated by CysLT(1) and CysLT(2) receptors. Here we report the discovery of 3-({[(1S,3S)-3-carboxycyclohexyl]amino}carbonyl)-4-(3-{4-[4-(cyclo-hexyloxy)butoxy]phenyl}propoxy) benzoic acid (HAMI3379), the first potent and selective CysLT(2) receptor antagonist. Experimental approach: Pharmacological characterization of HAMI3379 was performed using stably transfected CysLT(1) and CysLT(2) receptor cell lines, and isolated, Langendorff-perfused, guinea pig hearts. Key results: In a CysLT(2) receptor reporter cell line, HAMI3379 antagonized leukotriene D-4- (LTD4-) and leukotriene C-4- (LTC4-) induced intracellular calcium mobilization with IC50 values of 3.8 nM and 4.4 nM respectively. In contrast, HAMI3379 exhibited very low potency on a recombinant CysLT(1) receptor cell line (IC50 > 10 000 nM). In addition, HAMI3379 did not exhibit any agonistic activity on both CysLT receptor cell lines. In binding studies using membranes from the CysLT(2) and CysLT(1) receptor cell lines, HAMI3379 inhibited [3H]-LTD4 binding with IC50 values of 38 nM and > 10 000 nM respectively. In isolated Langendorff-perfused guinea pig hearts HAMI3379 concentration-dependently inhibited and reversed the LTC4-induced perfusion pressure increase and contractility decrease. The selective CysLT(1) receptor antagonist zafirlukast was found to be inactive in this experimental setting. Conclusions and implications: HAMI3379 was identified as a potent and selective CysLT(2) receptor antagonist, which was devoid of CysLT receptor agonism. Using this compound, we showed that the cardiac effects of CysLTs are predominantly mediated by the CysLT(2) receptor.