CYP3A4 Activity in Patients With Prostate Cancer Versus Male Patients With Other Solid Tumours

The hepatic enzyme, cytochrome P450 3A4 (CYP3A4) is important for the metabolism of many drugs including taxanes. Previous reported studies reported a decreases in docetaxel exposure in prostate cancer patients compared to patients with other solid tumours. The difference was 1.8-fold for intravenous administration and 2.8-fold for oral administration. The underlying mechanism for these observations remains to be elucidated. The lower docetaxel exposure with IV and oral docetaxel treatment might be related to a higher CYP3A4 activity in prostate cancer patients. Therefore, it is important to directly compare the CYP3A4 activity with a phenotyping test in prostate cancer patients and patients with other types of solid tumours. This is an in vivo phenotyping studying using midazolam as a probe for CYP3A4 activity in patients with prostate cancer and patients with other solid tumours. The primary objective is the comparison of CYP3A4 activity in prostate cancer patients versus male patients with other types of solid tumours by use of an oral midazolam phenotyping test. Secondary objectives are: (1) measurement of plasma concentrations of midazolam and it's two primary metabolites (1'-hydroxy midazolam and 4'-hydroxy midazolam), (2) determination of the metabolite pharmacokinetics of midazolam. (3) retrospective assessment of single nucleotide polymorphisms of CYP3A4. The exploratory objective is to differentiate between gastro-intestinal and hepatic CYP3A4 activity with oral and intravenous administration of midazolam.