Midazolam as a phenotyping probe to predict sunitinib exposure in patients with cancer

Purpose Patients treated with sunitinib show substantial inter-patient variability in drug exposure (~30–40 %), which is largely unexplained. Since sunitinib is metabolized by cytochrome P450(CYP)3A4, variability in the activity of this enzyme may explain a considerable proportion of this inter-patient variability. Midazolam is widely used as a phenotyping probe to assess CYP3A4-activity. The objective of this study was to prospectively evaluate the relationship between midazolam and sunitinib exposure. Additionally, the correlation between sunitinib trough levels and exposure and the influence of sunitinib on midazolam exposure was determined.