HEp2 cells were treated with ascending doses of test compounds and infected immediately thereafter with RSV A2 for five days. Parallel cytotoxicity assays were performed with uninfected cells. Relative viable cell counts were normalized to infected, untreated cells (0% viable) and uninfected, DMSO-treated cells (100% viable). The selected compounds showed dose-dependent inhibition of RSV-induced CPE with at least a ten-fold window between the antiviral effect and any observed cytotoxicity. Panels A, B, and C show compounds from Series 1, 2, and 3, respectively. EC50 and CC50 values are provided in Table 1.