Correlation between triphosphate levels versus potencies in human PBMCs. For the PBMC triphosphate level, different prodrugs (compounds 12, 5, 17, 14, and 18) were incubated in human PBMCs at 10 μM for 24 h, and then the intracellular triphosphate concentration was measured by LC-MS/MS. Data were obtained from at least two biological replicates. The DENV-2 EC50 was obtained from the human PBMCs plaque assay. See Materials and Methods for further details.