Midazolam may be used as a probe drug for CYP3A activity to predict docetaxel clearances, hence reducing interindividual variability. Homozygotes for CYP3A5*3 and C3435T of MDR1 are common in our population, and their effects on pharmacokinetics of relevant substrates should be studied further.

The objectives of the present study were (i) to study the pharmacogenetics of UGT1A1*6, UGT1A1*28 and ABCG2 c.421C> > > >A in three distinct healthy Asian populations (Chinese, Malays and Indians), and (ii) to investigate the polygenic influence of these polymorphic variants in irinotecan-induced neutropenia in Asian cancer patients. Pharmacokinetic and pharmacogenetic analyses were done after administration of irinotecan as a 90-min intravenous infusion of 375 mg/m 2 once every 3 weeks (n = = = = 45). Genotypic-phenotypic correlates showed a non-significant influence of UGT1A1*28 and ABCG2 c.421C> > > >A polymorphisms on the pharmacokinetics of SN-38 (P > > > > 0.05), as well as severity of neutropenia (P > > > > 0.05). Significantly higher exposure levels to SN-38 (P = = = = 0.018), lower relative extent of glucuronidation (REG; P = = = = 0.006) and higher biliary index (BI; P = = = = 0.003) were found in cancer patients homozygous for the UGT1A1*6 allele compared with patients harboring the reference genotype. The mean absolute neutrophil count (ANC) was 85% lower and the prevalence of grade 4 neutropenia (ANC ≤ ≤ ≤ ≤ 500/µ µ µ µL) was 27% in patients homozygous for UGT1A1*6 compared with the reference group. Furthermore, the presence of the UGT1A1*6 allele was associated with an approximately 3-fold increased risk of developing severe grade 4 neutropenia compared with patients harboring the reference genotype. These exploratory findings suggest that homozygosity for UGT1A1*6 allele may be associated with altered SN-38 disposition and may increase the risk of severe neutropenia in Asian cancer patients, particularly in the Chinese cancer patients who comprised 80% (n = = = = 36) of the patient population in the present study. (Cancer Sci 2007; 98: 1461-1467)

Clinical recovery after a small-for-size transplant is characterized by significant functional impairment associated with paradoxical histologic changes typical of ischemia. These changes apparently are due to graft injury, which can only be the result of small graft size. These findings have significant implications for the extension of LRLT to adults.

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