Effects of baicalein and fangchinoline on abemaciclib metabolism in vivo and in vitro and molecular docking analysis

The primary objective of this study was to investigate the effects of baicalein and fangchinoline on the metabolism of abemaciclib. We hypothesized that these two natural compounds could significantly affect the metabolism of abemaciclib by inhibiting the activity of the CYP3A4 enzyme, thus potentially increasing its concentration in the body. In vitro, rat liver microsomes (RLM) and human liver microsomes (HLM) were employed to explore the inhibitory effects and mechanisms of baicalein and fangchinoline on abemaciclib. In vivo, twelve healthy male Sprague-Dawley (SD) rats were randomly assigned to three groups: Group A (control group), Group B (baicalein), and Group C (fangchinoline). The concentrations of abemaciclib and its metabolite N-desethylabemaciclib (M2) were evaluated using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Finally, molecular docking method was employed to understand the interaction between abemaciclib and baicalein. It was indicated by the in vitro findings that both baicalein and fangchinoline inhibited abemaciclib metabolism in RLM through a mixed mechanism of competitive and non-competitive inhibition pathway. In HLM, baicalein inhibited abemaciclib metabolism by employing a hybrid mechanism of uncompetitive and non-competitive inhibition, while fangchinoline exhibited its inhibition in a competitive manner. In vivo, pharmacokinetic experiments revealed significant increases for AUC_(0-t) and AUC_(0-∞) of abemaciclib in Group B and Group C when compared to Group A, while the plasma clearance (CLz/F) of abemaciclib exhibited significant reductions. Moreover, molecular docking studies showed that both abemaciclib and baicalein docked to the active pocket of CYP3A4. This study demonstrated that the co-administration of baicalein or fangchinoline significantly affected the metabolism of abemaciclib, providing valuable insights for its clinical application.