Emerging adenosine receptor agonists: an update.

Adenosine receptors (ARs), the major targets of caffeine and theophylline, comprise four receptor subtypes designated as A(1), A(2A), A(2B) and A(3). Over a dozen AR agonists are currently in clinical trials for various conditions, including cardiac arrhythmias, neuropathic pain, myocardial perfusion imaging, cardiac ischemia, inflammatory diseases and cancer. Adenosine (nonselective), regadenoson (A(2A)) and dipyridamole (act indirectly via ARs) have received regulatory approval for clinical use. The present editorial will give a brief update on the current status of AR agonists in clinical trials.