Fig. 9.
PK-PD modeling process. Data from control group were used to develop the tumor natural growth model, and Koch’s model was chosen to describe the tumor growth. Data from AX monotherapy groups were used to develop the model of AX’s effect on tumor growth with parameter estimates from tumor natural growth model fixed. It was shown that AX could be best described to have tumor cell-damaging effect through an Emax E–C relation. With previous parameter estimates fixed, data from AX and DA combination therapy groups were used to describe the influence of DA on AX’s effect on tumor growth. The kmax enhancement and kC50 reduction effect models both fitted the data well. Finally, both two models were used to characterize the pool data from the whole PD study, and the models were then validated and compared to each other to choose a better one