Prediction of in silico fm
The fm can be also calculated based on predicted major CYP enzyme kinetics (in vivo Km and Vmax), combining compound’s structure and quantitative structure activity relationship (QSAR) model defaulted in ADMET Predictor module of GastroPlus. The clearance of each enzyme (ClCYP,i) is expressed as the Mieman equation:
ClCYP,i = Vmax,i / (Km,i+ S)
Then the fm of CYP3A4 (that is in silicofm ) could be shown in GastroPlus using the ClCYP3A4 divided by the sum of ClCYP,ifor each enzyme contributed on drug metabolism.