EC 50 , TC 50 , and Synergy Calculations EC 50 , TC 50 , and synergy calculations were done as described previously [10] . Briefly, EC 50 and TC 50 calculations for single agents were made by normalizing the NR data for each well against the cell and virus controls, which was assumed to represent 100% cell viability and 0% cell viability, respectively. Normalized data were plotted as percent cell viability versus compound concentration. The data points were then fitted using fourparameter curve fitting in Graphpad Prism (Graphpad Software, La Jolla, CA) to derive the EC 50 and TC 50 . Statistical comparisons between best-fit EC 50 values for any two curves were performed in Prism using the extra sum-of-squares F test; differences in EC 50 values between two curves with a P-value of ,0.05 were considered significant.