Subtle Structural Changes across the Boundary between A_2AR/A_2BR Dual Antagonism and A_2BR 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.