The TC 50 of amantadine as a single agent was 37-40 mg/mL, whereas the TC 50 of ribavirin and oseltamivir carboxylate as single agents were .100 mg/mL (Table S2) . These values are more than 10-fold higher than the highest concentration of each drug used in the combination experiments (Table S1 ). Furthermore, synergy analysis of the double and triple combinations revealed no synergistic cytotoxicity for any double combination or the TCAD regimen within the concentration ranges tested (data not shown). For example, cells treated with the TCAD regimen at the highest concentrations tested for all three drugs used in the combination experiments (3.2 mg/mL amantadine, 10 mg/mL ribavirin, and 3.2 mg/mL oseltamivir carboxylate) exhibited 97% viability, which was not statistically different than the cell control (P = 0.47 as determined by Student's t-test, Figure S4 ).