Inhibitory effect of Schisandrin on the pharmacokinetics of poziotinib in vivo and in vitro by UPLC-MS/MS

Background: As a pan-HER tyrosine kinase inhibitor with a promising application prospect, poziotinib is likely to be coadministered with Schisandrins in clinical treatment due to its anticancer activities. Methods: Eighteen Sprague-Dawley rats were randomly divided into three groups: Schisandrin A group and Schisandrin B group (20 mg/kg daily for 1 week), and control group (vehicle). On day 8, poziotinib (2 mg/kg) was administered by oral gavage 30 min later. An in vitro study was developed to identify the possible mechanisms of Schisandrins on poziotinib metabolism. All analytes were detected by UPLC/MS-MS, and molecular docking was performed by AutoDock Tools. Results: When rats were preadministered with Schisandrin A, AUC((0-infinity)) and Cmax of poziotinib were obviously increased by 0.79- and 1.17-fold, whereas the Vz/F and CLz/F values were dramatically decreased. The results in Schisandrin B group presented similarly. Both Schisandrin A and Schisandrin B were mixed inhibitors of poziotinib in RLMs, and Schisandrin B showed stronger inhibitory activity with IC50 values of 2.55 mu M for M1 and 6.97 mu M for M2. Molecular docking analysis demonstrated that Schisandrin A and Schisandrin B exhibited a strong binding ability towards CYP2D6 as compared to CYP3A4. Conclusion: All results provided the direct evidence of the pharmacokinetic drug-drug interactions (DDIs) between Schisandrin and poziotinib. Thus, particular attention should be paid when poziotinib is taken together with Schisandrins in clinical practice.