Figure 4. Demonstration of QSAR using a small panel of RSV fusion inhibitors.

(A) Chemical structures of the inhibitors (BTA-1 to 7 and TMC-353121) used in the assay validation. (B–D) Tabular IC₅₀ and corresponding scatter plots demonstrating a high correlation between the impedance based assays, whether in 96- or 384-well format with other standard assays over a wide range of inhibitor potencies. Tabulated summary of compound IC₅₀ or EC₅₀ values (log₁₀ M, SE shown in parentheses) measured either by cellular electrical impedance (in 96- and 384-well formats), luciferase reporter cell content mixing assay or a cytopathic effect (CPE) assay. A spread of IC₅₀ values over three orders of magnitude was observed using both fusion assays against live virus infection in a 96-well format and a spread of two orders of magnitude is observed for transiently expressed recombinant F (recF) based fusion assays in a 384-well format. The SE reported for the impedance fusion assay is generally smaller than the corresponding luciferase reporter, cell content mixing assay. R² values shown were obtained via linear regression analysis.