RT Journal Article SR Electronic T1 In Vitro Pharmacological Profile of KW-6356, a Novel Adenosine A2A Receptor Antagonist/Inverse Agonist JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 311 OP 324 DO 10.1124/molpharm.122.000633 VO 103 IS 6 A1 Yutaro Ohno A1 Michihiko Suzuki A1 Hidetsugu Asada A1 Tomoyuki Kanda A1 Mayumi Saki A1 Hikaru Miyagi A1 Mai Yasunaga A1 Chiyo Suno A1 So Iwata A1 Jun-ichi Saito A1 Shinichi Uchida YR 2023 UL http://molpharm.aspetjournals.org/content/103/6/311.abstract AB KW-6356 is a novel adenosine A2A (A2A) receptor antagonist/inverse agonist, and its efficacy as monotherapy in Parkinson’s disease (PD) patients has been reported. Istradefylline is a first-generation A2A receptor antagonist approved for use as adjunct treatment to levodopa/decarboxylase inhibitor in adult PD patients experiencing “OFF” episodes. In this study, we investigated the in vitro pharmacological profile of KW-6356 as an A2A receptor antagonist/inverse agonist and the mode of antagonism and compared them with istradefylline. In addition, we determined cocrystal structures of A2A receptor in complex with KW-6356 and istradefylline to explore the structural basis of the antagonistic properties of KW-6356. Pharmacological studies have shown that KW-6356 is a potent and selective ligand for the A2A receptor (the −log of inhibition constant = 9.93 ± 0.01 for human receptor) with a very low dissociation rate from the receptor (the dissociation kinetic rate constant = 0.016 ± 0.006 minute−1 for human receptor). In particular, in vitro functional studies indicated that KW-6356 exhibits insurmountable antagonism and inverse agonism, whereas istradefylline exhibits surmountable antagonism. Crystallography of KW-6356- and istradefylline-bound A2A receptor have indicated that interactions with His2506.52 and Trp2466.48 are essential for the inverse agonism, whereas the interactions at both deep inside the orthosteric pocket and the pocket lid stabilizing the extracellular loop conformation may contribute to the insurmountable antagonism of KW-6356. These profiles may reflect important differences in vivo and help predict better clinical performance.SIGNIFICANCE STATEMENT KW-6356 is a potent and selective adenosine A2A receptor antagonist/inverse agonist and exhibits insurmountable antagonism, whereas istradefylline, a first-generation adenosine A2A receptor antagonist, exhibits surmountable antagonism. Structural studies of adenosine A2A receptor in complex with KW-6356 and istradefylline explain the characteristic differences in the pharmacological properties of KW-6356 and istradefylline.