CYP3A5 variant allele frequencies in Dutch Caucasians

BACKGROUND: Enzymes of the cytochrome P450 3A (CYP3A) family are responsible for the metabolism of >50% of currently prescribed drugs. CYP3A5 is expressed in a limited number of individuals. The absence of CYP3A5 expression in approximately 70% of Caucasians was recently correlated to a genetic polymorphism (CYP3A5*3). Because CYP3A5 may represent up to 50% of total CYP3A protein in individuals polymorphically expressing CYP3A5, it may have a major role in variation of CYP3A-mediated drug metabolism. Using sequencing, have been identified (Hustert et al. Pharmacogenetics 2001;11:773-9; Kuehl et al. Nat Genet 2001;27:383-91) variant alleles *2 through *7 for CYP3A5. Detection of CYP3A5 variant alleles, and knowledge about their allelic frequency in specific ethnic groups, is important to establish the clinical relevance of screening for these polymorphisms to optimize pharmacotherapy. METHODS: In a group of 500 healthy Dutch Caucasian blood donors, we determined the allelic frequency of the CYP3A5*2, *3, *4, *5, *6, and *7 alleles by use of newly developed PCR-restriction fragment length polymorphism assays. RESULTS: The frequency of the defective CYP3A5*3 allele in the Dutch Caucasian population was 91%, followed by the CYP3A5*2 (1%) and CYP3A5*6 (0.1%) alleles. The CYP3A5*4, *5, and *7 alleles were not detected. CONCLUSIONS: On the basis of its allelic frequency, screening for the CYP3A5*3 allele in the Caucasian population is extremely relevant. In addition, screening for the CYP3A5*2 allele may be taken into consideration in individuals heterozygous for the CYP3A5*3 allele. The CYP3A5*4, *5, *6, and *7 alleles have low allelic frequencies that do not support initial screening

The interactions of age, genetics, and disease severity on tacrolimus dosing requirements after pediatric kidney and liver transplantation

Purpose: In children, data on the combined impact of age, genotype, and disease severity on tacrolimus (TAC) disposition are scarce. The aim of this study was to evaluate the effect of these covariates on tacrolimus dose requirements in the immediate post-transplant period in pediatric kidney and liver recipients. Methods: Data were retrospectively collected describing tacrolimus disposition, age, CYP3A5 and ABCB1 genotype, and pediatric risk of mortality (PRISM) scores for up to 14 days post-transplant in children receiving liver and renal transplants. Initial TAC dosing was equal in all patients and adjusted using therapeutic drug monitoring. We determined the relationship between covariates and tacrolimus disposition. Results: Forty-eight kidney and 42 liver transplant recipients (median ages 11.5 and 1.5 years, ranges 1.5-17.7 and 0.05-14.8 years, respectively) received TAC post-transplant. In both transplant groups, younger children (<5 years) needed higher TAC doses than older children [kidney: 0.15 (0.07-0.35) vs. 0.09 (0.02-0.20) mg/kg/12h, p = 0.046, liver: 0.12 (0.04-0.32) vs. 0.09 (0.01-0.18) mg/kg/12h, p

MDR1 gene polymorphisms are associated with neuropsychiatric adverse effects of mefloquine.

BACKGROUND: Mefloquine, a drug used for treatment and prophylaxis of malaria, is known for its neuropsychiatric adverse effects. We hypothesized that neuropsychiatric adverse effects of mefloquine are associated with polymorphisms in the MDR1/ABCB1 gene that encodes for the efflux pump P-glycoprotein. METHODS: The association between MDR1 C1236T, G2677T, and C3435T single-nucleotide polymorphisms and the occurrence of neuropsychiatric adverse effects was examined in a prospective cohort study of 89 healthy white travelers taking mefloquine. RESULTS: Of the subjects, 27 (28%) reported neuropsychiatric adverse effects, women significantly more frequently than men. Allele frequencies of the C1236T, G2677T, and C3435T polymorphisms were similar to those found in other white populations, and there was no significant association between any of the individual polymorphisms and neuropsychiatric adverse effects. However, women with the 1236TT, 2677TT, and 3435TT genotypes had a higher risk of neuropsychiatric adverse effects than the reference groups of women with heterozygous and homozygous CC or GG genotypes, with odds ratios of 6.3 (95% confidence interval [CI], 1.1-36.9), 10.5 (95% CI, 1.1-100.6), and 5.4 (95% CI, 1.1-30.0), respectively. The association for women homozygous for the 1236-2677-3435 TTT haplotype was even stronger (P = .004) than the effect of any of the individual polymorphisms. No associations with mefloquine blood levels were observed. CONCLUSION: In this study the MDR1 1236TT, 2677TT, and 3435TT genotypes, along with the 1236-2677-3435 TTT haplotype, were associated with neuropsychiatric adverse effects of mefloquine in women. MDR1 polymorphisms may play an important role in predicting the occurrence of neuropsychiatric adverse effects of mefloquine, particularly in female travelers

A new CYP3A5 variant, CYP3A5*11, is shown to be defective in nifedipine metabolism in a recombinant cDNA expression system

A new CYP3A5 variant, CYP3A5*11, was found in a white European subject by DNA sequencing. The CYP3A5*11 allele contains a single nucleotide polymorphism (SNP) (g.3775A>G) in exon 2, which results in a Tyr53Cys substitution, and a g.6986A>G splice change, the latter SNP previously reported in the defective CYP3A5*3 allele. However, the CYP3A5*3 is not a null allele because this variant is associated with leaky splicing, resulting in small amounts of functional protein still being produced. Therefore, we constructed a cDNA coding for the newly identified CYP3A5.11 protein by site-directed mutagenesis, expressed it in Escherichia coli, and partially purified it. Whereas bacteria transformed with wild-type CYP3A5*1 cDNA expressed predominantly cytochrome P450 (P450), those transfected with CYP3A5*11 expressed a significant amount of denatured cytochrome P420 in addition to P450, suggesting the protein to be unstable. CYP3A5.11 exhibited a 38% decrease in the Vmaxfor nifedipine metabo

A new functional CYP3A4 intron 6 polymorphism significantly affects tacrolimus pharmacokinetics in kidney transplant recipients.

Tacrolimus (Tac) is a potent immunosuppressant with considerable toxicity. Tac pharmacokinetics varies between individuals and thus complicates its use in preventing rejection after kidney transplantation. This variability might be caused by genetic polymorphisms in metabolizing enzymes

Interpatient variability in the pharmacokinetics of the HIV non-nucleoside reverse transcriptase inhibitor efavirenz: the effect of gender, race, and CYP2B6 polymorphism

Contains fulltext : 50827.pdf (publisher's version ) (Closed access)AIMS: To characterize the demographic and pharmacogenetic factors that influence interpatient variability in the plasma concentrations of the HIV non-nucleoside reverse transcriptase inhibitor efavirenz. METHODS: Data from all samples analyzed for efavirenz in our TDM service in 2002 and 2003 were reviewed. Information on gender, age, body weight, height, race, hormonal contraceptive use (in a subset of patients), and time between sampling and last intake was recorded. PCR-restriction fragment length polymorphism analysis was performed to detect the cytochrome P450 2B6 (CYP2B6) C1459T variant (present in CYP2B6*6 and CYP2B6*7) which is associated with low CYP2B6 activity. RESULTS: A total of 255 patients were included in this analysis. The median plasma efavirenz concentration was 2.50 (interquartile range: 1.85-3.55) mg l(-1). Eight patients (3.1%) were considered to have a subtherapeutic plasma concentration (4.0 mg l(-1)). Gender, time after last intake, and race were the only factors that were significantly related to plasma efavirenz concentration in a multivariate analysis. No influence was observed for body weight, hormonal contraceptive use, and the presence of the CYP2B6 C1459T polymorphism. CONCLUSIONS: Gender and race are important factors in determining interpatient variability in plasma efavirenz concentrations which were unaffected by the presence of the CYP2B6 C1459T polymorphism. Physicians should be particularly alert for signs of efavirenz-induced toxicity in females and non-Caucasian patients