Quantification and comparison of cellular nucleoside triphosphate (TP) levels of R1479, 2′F-4′N3-C, and 2′diF-4′N3-C. (a). R1479-TP levels were measured in 4 different cell types (HeLa, Huh7, SK-N-MC, and NCI-H358) after 24 h of treatment at 50 μM. (b) Levels of triphosphorylated R1479, 2′F-4′N3-C, and 2′diF-4′N3-C in HeLa cells (black bars) and NCI-H358 cells (gray bars) after 24 h of treatment at 50 μM. Graphs and error bars indicate mean values and standard deviations for each compound in each cell line performed at minimum in biological triplicates.