ADA and neoplasm: Different strategies have been adopted to modulate the immunosuppressive effect of adenosine, such as inhibiting ectonucleotidases activity to reduce the conversion of ATP into adenosine, blocking the binding of adenosine with T cell receptor, and degrading intracellular adenosine using adenosine deaminase (ADA).[6] However, these strategies have the limitations of poor selectivity and low safety because the antagonists and enzymes show unsatisfactory accumulation in targeting tumor sites.