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

Aberrantly elevated adenosine in the tumor microenvironment exerts its immunosuppressive functions through adenosine receptors A 2A R and A 2B R. Antagonism of A 2A R and A 2B R 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 2A R/A 2B R activity and selectivity of novel 2-aminopyrimidine compounds. Substituting indole at the 4-/5-position produced potent A 2A R/A 2B R dual antagonism, whereas the 6-position of indole substitution gave highly selective A 2B R 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 2A R. Of note, dual A 2A R/A 2B R 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 2A R/A 2B R or A 2B R antagonists by fine-tuning structural modification.