Chirality-Guided Optimization of A_2A Adenosine Receptor Antagonists for Enhanced Metabolic Stability and Antitumor Efficacy

Blockade of the A_2A adenosine receptor (A_2AAR) by small-molecule antagonists holds promise for enhancing the efficacy of immune checkpoint inhibitors such as PD-L1 antibodies. However, many A_2AAR antagonists suffer from limited clinical success due to poor metabolic stability. In this study, we introduce chirality into the A_2AAR antagonist scaffold to address this challenge. This approach led to the discovery of (<i>S</i>)-<b>E8</b>, a chiral compound with markedly improved binding affinity, cellular activity, and <i>in vivo</i> potency compared with AZD4635, a Phase II clinical candidate. In contrast, its enantiomer (<i>R</i>)-<b>E8</b> displays rapid metabolism and low efficacy, highlighting the importance of stereochemistry for therapeutic performance. Mechanistic studies identified CYP1A2 as the primary enzyme driving the metabolic differences among the enantiomers. These findings underscore the value of chirality-guided design in optimizing drug-like properties and reveal CYP1A2's pivotal role in enantioselective metabolism, offering a promising direction for the development of next-generation A_2AAR antagonists.