Structural insight into the dual-antagonistic mechanism of AB928 on adenosine A₂ receptors

The adenosine subfamily G protein-coupled receptors A_2AR and A_2BR have been identified as promising cancer immunotherapy candidates. One of the A_2AR/A_2BR dual antagonists, AB928, has progressed to a phase II clinical trial to treat rectal cancer. However, the precise mechanism underlying its dual-antagonistic properties remains elusive. Herein, we report crystal structures of the A_2AR complexed with AB928 and a selective A_2AR antagonist 2–118. The structures revealed a common binding mode on A_2AR, wherein the ligands established extensive interactions with residues from the orthosteric and secondary pockets. In contrast, the cAMP assay and A_2AR and A_2BR molecular dynamics simulations indicated that the ligands adopted distinct binding modes on A_2BR. Detailed analysis of their chemical structures suggested that AB928 readily adapted to the A_2BR pocket, while 2–118 did not due to intrinsic differences. This disparity potentially accounted for the difference in inhibitory efficacy between A_2BR and A_2AR. This study serves as a valuable structural template for the future development of selective or dual inhibitors targeting A_2AR/A_2BR for cancer therapy.