Establishment and assessment of a novel in vitro bio-PK/PD system in predicting the in vivo pharmacokinetics and pharmacodynamics of cyclophosphamide.

1. A novel bio-pharmacokinetic/pharmacodynamic (PK/PD) system was established and assessed in predicting the PK parameters and PD effects of the model drug cyclophosphamide (CP) considering the interrelationships between drug metabolism, pharmacological effects and dynamic blood circulation processes in vitro. 2. The system contains a peristaltic pump, a reaction chamber with rat liver microsomes (RLMs) encapsulated in pluronic F127-acrylamide-bisacrylamide (FAB) hydrogels, an effector cell chamber and a recirculating pipeline. The metabolism and pharmacological effects of CP (5, 10 and 20 mM) were measured by HPLC and MTT assay. A mathematical model based on mass balance was used to predict the in vitro clearance of CP. In vivo clearance of CP was estimated by in vitro to in vivo extrapolations (IVIVE) and simulations using Simcyp® software. 3. The predicted in vivo clearance of CP at concentrations of 5, 10 and 20 mM was 11.36, 10.12 and 10.68 mL/min/kg, respectively, within two-fold differences compared with the reported 11.1 mL/min/kg. The survival ratio of effector cells during the metabolism and circulation of CP was significantly enhanced. 4. This system may serve as an alternative approach to predict in vivo metabolism, pharmacological effects and toxicity of drugs, ensuring an efficient drug screening process.