Structural insights into dual-antagonize mechanism of AB928 on adenosine A2 receptors

The adenosine subfamily G protein-coupled receptors A2AR and A2BR were identified as promising candidates for cancer immunotherapy within recent years. One of the A2AR/A2BR dual antagonist, AB928, has progressed to phase II clinic trial for the treatment of rectal cancer. However, the precise mechanism underlying its dual-antagonistic properties remains elusive. Herein, we report crystal structures of A2AR in complex with AB928 and a selective A2AR antagonist, 2-118. The structures reveal a common binding mode on A2AR, wherein the ligands establish extensive interactions with residues from both the orthosteric pocket and the secondary pocket. Conversely, the cAMP assay together with molecular dynamics simulations conducted on both A2AR and A2BR indicate that the ligands adopt distinct binding modes on A2BR. Detailed analysis of their chemical structures suggests that AB928 can readily adapt to the A2BR pocket, while 2-118 cannot due to its intrinsic differences. This disparity potentially accounts for their divergent inhibitory efficacies between A2BR and A2AR. The findings from this study can serve as valuable structural templates for future development of selective or dual inhibitors targeting A2AR/A2BR in the context of cancer therapy.