Curve-fitting, half-maximal Effective Concentration (EC50) and 50% Cytotoxic Concentration (CC50) determination and Selectivity Index (SI)

A custom hyperbolic fit function [y = a+bx/(1+cx)] in Igor Pro software (WaveMetrics, Inc., Portland, OR, USA) was used for fitting DENV-2 NS1 expression and PF-429242 inhibition curves and for determining EC₅₀ value. The same function was used for fitting cell viability (O.D. at 490 nm) when treated with PF-429242 or DMSO. The reported EC₅₀ and CC₅₀ values are the average of the values calculated from at least two independent experiments (± SEM). The selectivity index (SI) was determined as the ratio of CC₅₀ to EC₅₀ concentration.