Cited 48 times since 2005 (2.4 per year) source: EuropePMC Clinical cancer research : an official journal of the American Association for Cancer Research, Volume 11, Issue 20, 1 1 2005, Pages 7398-7404 Effect of common CYP3A4 and CYP3A5 variants on the pharmacokinetics of the cytochrome P450 3A phenotyping probe midazolam in cancer patients. Lepper ER, Baker SD, Permenter M, Ries N, van Schaik RH, Schenk PW, Price DK, Ahn D, Smith NF, Cusatis G, Ingersoll RG, Bates SE, Mathijssen RH, Verweij J, Figg WD, Sparreboom A
Purpose
To evaluate the effect of naturally occurring variants in genes encoding the cytochrome P450 (CYP) isoforms CYP3A4 and CYP3A5 in patients with cancer receiving midazolam as a phenotyping probe.
Experimental design
Five variants in CYP3A4 and CYP3A5 were evaluated in 58 patients (21 women and 37 men) receiving a short i.v. bolus of midazolam (dose, 0.0145 or 0.025 mg/kg). Midazolam concentrations in plasma were determined using liquid chromatography-mass spectrometry, and pharmacokinetic variables were calculated using noncompartmental analysis. Genomic DNA was characterized for the variants by PCR-RFLP, and all genotypes were confirmed by direct nucleotide sequencing.
Results
The mean clearance of midazolam was 24.4 +/- 9.12 L/h, and phenotypic CYP3A activity varied about 4-fold in this population (range, 10.8-44.3 L/h). There were six carriers of the CYP3A4*1B allele (allele frequency, 0.061). No variant alleles for CYP3A4*17, CYP3A4*18A, or CYP3A5*6 were identified. Forty-eight of the 58 patients were homozygous variant for CYP3A5*3C, eight were heterozygous, and two were homozygous wild type (allele frequency, 0.897). No associations were noted between any of the studied genotypes and the phenotypic measures (P > or = 0.16). Likewise, a common variant in exon 26 in the gene encoding P-glycoprotein [i.e., ABCB1 (MDR1) 3435C>T] that was previously reported to be linked to CYP3A4 mRNA levels was unrelated to any of the studied phenotypic measures (P > or = 0.49).
Conclusions
The studied genetic variants in CYP3A4 and CYP3A5 are unlikely to have an important functional significance to phenotypic CYP3A activity in patients with cancer.
