To investigate the potency of an adenosine A 3 receptor (A 3 AR) antagonist as an anti- asthmatic drug, a novel series of 4-phenyl-5-pyridyl-1, 3-thiazole derivatives was synthesized and evaluated in human adenosine A 1, A 2A and A 3 receptor and rat adenosine A 3 receptor binding assays. From investigation of the SAR study, compound 7af was identified as a highly potent human and rat A 3 AR antagonist. This compound ...