Orally bioavailable allosteric CCR8 antagonists inhibit dendritic cell, T cell and eosinophil migration

The chemokine receptor CCR8 is associated with asthma. Herein, we describe that both mature and immature dendritic cells (DC) express CCR8, whereas only mature DC migrate towards CCL1. Moreover, transient LPS challenge significantly down-regulates CCR8 expression hence attenuating CCL1 chemotaxis. To inhibit CCR8 pathophysiology, we recently developed a novel series of small molecule CCR8 antagonists containing a diazaspiroundecane scaffold, which had micromolar potency. However, these first generation antagonists had high lipophilicity that endowed the compounds with poor physicochemical properties, and were thus not suitable for further development. By introducing polar bicyclic groups on the N-benzyl substituent and building in further polar interactions on the amide group we now show second generation diazospiroundecane antagonists with significantly improved overall properties. Potency is substantially improved from micromolar to nanomolar potency in CCR8 binding and inhibition of chemotaxis in human primary T cells, DC and in an eosinophil cell line. In addition to high potency, the most attractive antagonist, AZ084 showed excellent selectivity, high metabolic stability in vitro and an attractive in vivo PK profile with a long half-life in rat. Interestingly, in ligand saturation experiments and in wash-off experiments. CCL1 was shown to have two binding sites to CCR8 with K-d at 1.2/68 pM respectively, and on-off rates of 0.004 and 0.0035/0.02 pM min, respectively. The lead antagonist, AZ084, appears to act as an allosteric inhibitor with a K-i at 0.9 nM. Taken together, we herein report a novel oral allosteric CCR8 antagonist with predicted low once-daily dosing capable of potent inhibition of both human T cell and DC functions. (C) 2012 Elsevier Inc. All rights reserved.