Fig. 1.

Surrogate viral load data generated assuming PEG-IFNα2b was given on days 0, 7, 14, 21 and 28 and HCV RNA was sampled at day 0, 1, 2, 3, 4, 7, 14, 21 and 28. Closed circles represent the surrogate data obtained by numerical simulation of the PK/PD model [2,4]. Solid lines in the top row show the viral kinetics predicted by the CE model [1] with the best-fit parameters. Here, the assumed detection limit of the HCV RNA assay is 50 IU/mL (dashed lines). The dotted and solid lines in bottom row are the actual effectiveness and the estimated effectiveness by the CE model, respectively. The parameters used to generate the surrogate data in the figures are: (a) k_a = 2/day, EC₅₀ = 0.1 µg/L, k_e = 0.2/day, n = 1, (b) k_a = 7/day, EC₅₀ = 0.6 µ/L, k_e = 0.7/day, n = 1, (c) k_a = 7/day, EC₅₀ = 0.4 µg/L, k_e = 0.2/day, n = 3 and (d) k_a = 0.19/day, EC₅₀ = 0.6 µg/L, k_e = 0.2/day, n = 3, respectively. The viral clearance rate, c, was fixed at 9.9/day. The estimated values of δ (δ̂), average of estimated effectiveness (ɛ̂ _a) and the average of actual effectiveness (ε_a) for the four panels were

Panels	(a)	(b)	(c)	(d)
δ/(day)	0.30	0.15	0.26	0.57
ɛ̂a	0.88	0.41	0.88	0.36
εa	0.88	0.24	0.83	0.58