Inhibition of Axitinib on Buspirone Metabolism in vitro and in vivo.

Objective: To evaluate the effect of axitinib on buspirone metabolism in vitro and in vivo. Methods: A microsome incubation assay was performed to study the effect and mechanism of axitinib on buspirone metabolizing. In vivo, buspirone was administered with or without axitinib to Sprague-Dawley rats. Plasma samples were collected and subjected to ultra-performance liquid chromatography-tandem mass spectrometry. Results: In both human liver microsomes (HLMs) and rat liver microsomes (RLMs), axitinib (100 µM) decreased buspirone hydroxylation and N-dealkylation by >85%. Axitinib inhibited buspirone hydroxylation and N-dealkylation, with an IC50 of 15.76 and 9.74 for RLMs, and 10.63 and 9.902 for HLMs. Axitinib showed noncompetitive inhibition of both 6'-hydroxylation and N-dealkylation. Moreover, coadministration of axitinib and buspirone led to an increase in the maximum plasma concentration (C max ) and area under the plasma concentration-time curve (AUC) of buspirone by 4.3- and 5.3-fold, respectively, compared with the control group. Conclusion: Axitinib inhibited buspirone metabolism in vivo and in vitro, which increases the risk of the side effects of buspirone in the clinic. When coadministered with axitinib, a lower dosage of buspirone should be defined to avoid a toxic response. Axitinib is suspected to function as an inhibitor of CYP3A4.

Evaluation of the inhibition effects of apatinib on human and rat cytochrome P450.

Apatinib, a small molecule anti-angiogenic drug, is proven to be safe and effective for treatment of advanced gastric cancer (AGC). It is also a single drug that significantly prolongs survival after failure of standard chemotherapy for AGC, which has attracted the research interest. The purpose of this study is to evaluate the inhibition effects of apatinib on human and rat cytochrome P450, including CYP3A2/4, CYP2B1/6, CYP2C9/11, CYP2D1/6, and CYP2E1. The IC50 and IC50-shift results indicated that apatinib might not be a time-dependent inhibitor. Apatinib was a weak inhibitor of human CYP2E1 (IC50>10 µM) but inhibited CYP2B6/2B1 and CYP2D6/2D1 in a competitive way (Ki = 3.84/0.59 and 5.41/0.87 µM), and inhibited CYP3A4/3A2 and rat CYP2E1 in a mixed way (Ki = 11.50/1.83 and 13.06 µM). On CYP2C9, apatinb exhibited the noncompetitive inhibition (Ki = 0.71 µM) while it inhibited CYP2C11 uncompetitively (Ki = 3.30 µM).