The development of selective agonists and antagonists of the four subtypes of adenosine receptors (ARs) has been extensively explored.1–3 Antagonists of the Gs protein-coupled A2AAR are sought for as agents for treating neurodegenerative conditions such as Parkinson's disease (PD) and Alzheimer's disease (AD), and for coadministration with cancer immunotherapy.4–7 Caffeine, the most consumed psychostimulant in the world, acts as a nonselective AR antagonist and readily enters the brain to antagonize the A2AAR at doses generally consumed. The gene discussed is AR; the disease is Parkinson disease.