ADK and COVID-19: Based on these current results and previous data [24–27], we can conclude that, first, riboprine and forodesine can be further in vivo and clinically investigated for repurposing against COVID-19 and, second, the expected potent clinical inhibitory effects of riboprine and forodesine against SARS-CoV-2 replication may be principally attributed to the triple synergistic inhibitory activities against the three enzymes RdRp, ExoN, and adenosine kinase (ADK), i.e., may be closely related to RdRp, ExoN, and ADK inhibitory activities of riboprine and forodesine.