Subtle Structural Changes across the Boundary between A2AR/A2BR Dual Antagonism and A2BR Antagonism: A Novel Class of 2-Aminopyrimidine-Based Derivatives

Aberrantly elevated adenosine in the tumor microenvironment exerts its immunosuppressive functions through adenosine receptors A_2AR and A_2BR. Antagonism of A_2AR and A_2BR has the potential to suppress tumor growth. Herein, we report a systemic assessment of the effects of an indole modification at position 4, 5, 6, or 7 on both A_2AR/A_2BR activity and selectivity of novel 2-aminopyrimidine compounds. Substituting indole at the 4-/5-position produced potent A_2AR/A_2BR dual antagonism, whereas the 6-position of indole substitution gave highly selective A_2BR antagonism. Molecular dynamics simulation showed that the 5-cyano compound 7ai had a lower binding free energy than the 6-cyano compound 7aj due to water-bridged hydrogen bond interactions with E169 or F168 in A_2AR. Of note, dual A_2AR/A_2BR antagonism by compound 7ai can profoundly promote the activation and cytotoxic function of T cells. This work provided a strategy for obtaining novel dual A_2AR/A_2BR or A_2BR antagonists by fine-tuning structural modification.