Impact of CYP3A5 and CYP3A4 gene polymorphisms on dose requirement of calcineurin inhibitors, cyclosporine and tacrolimus, in renal allograft recipients of North India

The present study investigated pharmacogenetic associations of common cytochrome P450 3A (CYP3A5 and CYP3A4) polymorphisms with dose requirements of calcineurin inhibitors, cyclosporine (CsA) and tacrolimus (Tac) in renal transplant recipients of North India. Two hundred twenty four patients on CsA and 73 patients on Tac-based immunosuppression regimen were genotyped for CYP3A5*3 (6986A>G) and CYP3A4*1B (-290A>G) and correlated with CsA/Tac dose requirement (mg/kg/day) and dose-adjusted CsA (C₂)/Tac (T ₀) blood levels (concentration/dose ratio) at 1 month and 3 months posttransplantation. The dose-adjusted levels were significantly lower in CYP3A5 expressers for CsA (p = 0.037; 3 months) and Tac (p < 0.001; 1 month and p < 0.001; 3 months) compared to the non-expressers, suggesting that for a given dose their CsA/Tac blood concentration is lower. The CYP3A5 non-expresser genotype was associated with reduced risk for allograft rejection (HR-0.18, 95% CI 0.03–0.99). No influence of CYP3A4*1B on CsA/Tac pharmacokinetics was observed. CYP3A5 expressers were associated with significantly lower dose-adjusted CsA/Tac concentrations and higher allograft rejection episodes in patients on Tac therapy.     

Effect of genetic polymorphisms of CYP3A5 and MDR1 on cyclosporine concentration during the early stage after renal transplantation in Chinese patients co-treated with diltiazem

Objective  The aim of this study was to assess the influence of the cytochrome (CYP450)3A5 and multidrug resistance (MDR1) gene polymorphisms on cyclosporine A (CsA) trough concentration during the early stage after renal transplantation in Chinese patients co-treated with diltiazem. Methods   CYP3A5*3 (A6986G) and MDR1 C1236T, G2677T/A and C3435T polymorphisms were determined by PCR followed by restriction fragment length polymorphism (RFLP) analysis. A total of 112 Chinese renal transplant patients were enrolled in the study. The whole blood trough concentration was measured at 7 days after transplantation, and the dose-adjusted trough levels were compared among the different genotypes. Results  The dose-adjusted trough levels of CsA were significantly higher in MDR1 2677TT carriers than in GG plus GT carriers (59.5 ± 15.9 vs. 34.5 ± 9.4 vs. 43.2 ± 13.6 ng/mL per mg per kg; P < 0.0001). In patients who were co-treated with diltiazem, compared with carriers of haplotype T-T-C, the carriers of haplotype C-G-C and haplotype T-G-T had significantly lower dose-adjusted trough blood concentrations of CsA than the non-carrier group (P = 0.002, P = 0.000 and P = 0.000, respectively). However, no evidence was found that there was a relationship between the CYP3A5*3, MDR1 C1236T and MDR1 C3435T polymorphisms and CsA dose-adjusted trough concentrations. Conclusion  This study demonstrated that the G2677T/A single nucleotide polymorphisms in MDR1 and MDR1 haplotypes C-G-C, T-G-T and T-T-C are associated with the CsA concentration during the very early post-transplant period in Chinese renal transplant patients co-treated with diltiazem. These polymorphisms may be useful for determining the appropriate initial dose of CsA after renal transplantation.     

CYP3A4*18B基因多态性与他克莫司血药浓度的相关性研究

目的:探讨中国汉族肾移植患者CYP3A 4* 18B基因型对术后1个月内他克莫司谷浓度的影响.方法:采用限制性片段长度多态性技术分析了30例汉族患者CYP3A4* 18B基因型,采用酶增强免疫测定技术测定患者他克莫司谷浓度.将血药浓度标准化后对不同基因型患者剂量调整谷浓度差异进行t检验.结果:测得CY P3A 4*18B等位基因频率为0.333,符合Hardy-Weinberg平衡.将患者分成*1/*1型慢代谢组和*1/*18B合并*18B/*18B型快代谢组,两组标准化谷浓度分别为(98.02±18.56) ng·kg·mL-1· mg-1和(62.91±18.15) ng· kg· mL-1· mg-1 (P＜0.01),慢代谢组的FK506剂量调整谷浓度显著高于快代谢组.结论:CYP3A 4* 18B基因多态性与他克莫司剂量调整谷浓度显著相关,该突变可能导致CYP3A4酶活性的提高.     

CYP3A5~*3和CYP3A4~*18B基因多态性对肾移植患者环孢素药代动力学的影响

目的回顾性研究肾脏移植后1mon,CYP3A5*3和CYP3A4*18B基因多态性对CsA药代动力学参数的影响。方法采用PCR-RFLP方法分析了63名肾脏移植患者CYP3A5*3和CYP3A4*18B基因型;荧光偏正免疫法用于检测肾移植患者静脉全血中的CsA浓度。结果在63名肾移植患者中,CYP3A5*3和CYP3A4*18B突变等位基因发生频率分别为0.770(95CI:0.767～0.773),0.235(95CI:0.235～0.241),而且这些等位基因表现出完全连锁不平衡。在移植术后1mon内,携带CYP3A4*1/*1野生型纯合子患者的C0以及剂量校正谷血浓度(C0/D)均明显高于携带CYP3A4*1/*18B杂合子或CYP3A4*18B/*18B突变型纯合子患者(P<0.05,Mann-WhitneyUtest);CYP3A5*1/*1基因型组的给药剂量明显高于CYP3A5*1/*3或CYP3A5*3/*3基因型组(P=0.004<0.01,Kruakal-Wallistest);CYP34*18B和CYP3A5*3联合考虑,对于CYP3A5表达组,同样发现C0、C0/D在CYP3A4*1/*1组C0以及C0/D均明显高于CYP3A4*1/*18B或CYP3A4*18B/*18B组(P<0.05,Mann-WhitneyUtest);而其他药动学参数在CYP3A5*3及CYP3A4*18B各组间相比差异则没有统计学意义。结论CYP3A5*3和(或)CYP3A4*18B基因多态性对肾移植后1monCsA药代动力学有一定影响,移植前CYP3A5*3基因型的分析仍需进一步研究。     

Effect of <Emphasis Type="Italic">CYP3A5*3</Emphasis> genotype on the pharmacokinetics and antiplatelet effect of clopidogrel in healthy subjects

Objective Clopidogrel is activated by cytochrome P450 3A (CYP3A) to generate an active metabolite that inhibits adenosine diphosphate (ADP)-induced platelet aggregation through irreversible binding to the platelet P2Y12 receptor. The objective of this study was to assess the effect of the CYP3A5 genotype on the pharmacokinetics and antiplatelet effect of clopidogrel in healthy subjects. Methods Twenty-two healthy subjects (CYP3A5*1/*1, n = 6; CYP3A5*1/*3, n = 8; CYP3A5*3/*3, n = 8) were recruited. After the administration of a loading dose of 300 mg of clopidogrel followed by 75 mg once daily for 6 days, plasma concentrations of clopidogrel and SR26334, an inactive metabolite, were measured for 24 h. The antiplatelet effect of clopidogrel was also measured, by determining the inhibition of ADP-induced platelet aggregation for 168 h, according to CYP3A5 genotype. Results Mean plasma concentration profiles of clopidogrel and SR26334 were comparable between CYP3A5 genotype groups. In addition, the CYP3A5 genotype did not affect the pharmacokinetics of either clopidogrel or SR26334. CYP3A5 genotype also did not modulate the inhibitory effect of clopidogrel on platelet aggregation. Conclusion The CYP3A5*3 genotype plays a minor role in causing interindividual variability of the disposition of clopidogrel and its antiplatelet effect in humans.     

Serum concentrations of sertraline and N-desmethyl sertraline in relation to CYP2C19 genotype in psychiatric patients

Objective  To investigate the impact of CYP2C19 genotype on serum concentrations of sertraline and N-desmethyl sertraline in psychiatric patients. Methods  Patients treated with sertraline (n = 121) were divided into six subgroups according to CYP2C19 genotype: CYP2C19*17/*17, CYP2C19*1/*17, CYP2C19*1/*1, CYP2C19*17/def, CYP2C19*1/def and CYP2C19def/def (def = allele encoding defective CYP2C19 metabolism, i.e. *2 and *3). Dose-adjusted serum concentrations were compared by linear mixed model analyses using the CYP2C19*1/*1 subgroup as reference. Results  Subgroups carrying one or two alleles encoding defective CYP2C19 metabolism achieved significantly higher mean dose-adjusted serum concentrations of sertraline and N-desmethyl sertraline compared to the CYP2C19*1/*1 subgroup (P < 0.05). The effect of CYP2C19 genotype was expressed as 3.2-fold (sertraline) and 4.5-fold (N-desmethyl sertraline) higher dose-adjusted serum concentrations in the CYP2C19def/def subgroup compared to the CYP2C19*1/*1 subgroup (P < 0.01). The CYP2C19*17 allele had no influence on the dose-adjusted serum concentrations of sertraline and N-desmethyl sertraline. Conclusion  The significantly higher serum concentrations associated with alleles encoding defective CYP2C19 metabolism might be of relevance for the clinical outcome of sertraline treatment.     

Effects of the CYP3A5 genotype on omeprazole sulfoxidation in CYP2C19 PMs

Objective Omeprazole is metabolized by the two cytochrome P450 isoforms, CYP3A (sulfoxidation) and CYP2C19 (hydroxydation). The aim of this study was to determine whether the CYP3A5 genotype is an important determinant of inter-individual variability of total CYP3A activity in vivo. Methods Plasma levels of omeprazole and omeprazole sulfone were analyzed by high-performance liquid chromatography in blood samples drawn 4–5 h after 43 CYP2C19 poor metabolizers (PMs) had ingested a single oral 40 mg dose of omeprazole. The CYP3A5*3 allele was identified using a PCR-restriction fragment length polymorphism assay. Results Among the 43 CYP2C19 PMs, 24 were CYP3A5*3/*3 carriers and 19 were CYP3A5*1 carriers (CYP3A5*1/*1 in one subject and CYP3A5*1/*3 in 18 subjects). No significant difference was found between the mean log10(metabolic ratio) of the CYP3A5*3/*3 carriers (0.314 ± 0.369) and CYP3A5*1 carriers (0.330 ± 0.313). Conclusions The CYP3A5 genotype was not an important factor underlying the inter-individual variation in the metabolic ratio of omeprazole to omeprazole sulfone in our study cohort, although genotype can be considered to be responsible for the inter-individual variation of many CYP3A substrates in vivo.     

Tacrolimus Elimination in Four Patients With a CYP3A5*3/*3 CYP3A4*22/*22 Genotype Combination

Cytochrome P450 3A5 (CYP3A5) and cytochrome P450 3A4 (CYP3A4) are the predominate enzymes responsible for tacrolimus metabolism. The presence of CYP3A4 and CYP3A5 genetic variants significantly affects tacrolimus clearance and dose requirements. CYP3A5*3 is a loss‐of‐function variant resulting in no CYP3A5 enzyme production. CYP3A4*22 is a variant that reduces production of functional CYP3A4 protein. Caucasians commonly carry these variant alleles but are very rarely homozygous for both CYP3A5*3 and CYP3A4*22. This report describes four kidney transplant recipients who carry a rare genotype combination (CYP3A5*3/*3 and CYP3A4*22/*22). These patients were identified from a larger cohort of Caucasian kidney transplant recipients (n=1366). To understand the significance of this genotype combination on tacrolimus troughs and doses, we compared these patients to recipients without this combination. Patients homozygous for both variants are at risk for profound reductions in metabolism of CYP3A substrates. A 342% and a 90.6% increase in the median dose‐normalized trough was observed, when the CYP3A5*3/*3 and CYP3A4*22/*22 genotype combination was compared to the CYP3A5*1/*1 and CYP3A4*1/*1 genotype combination and the CYP3A5*3/*3 and CYP3A4*1/*1 genotype combination, respectively. These four individuals only required on average 2.5 mg/day of tacrolimus. Knowledge of these genotypes would be useful in selecting appropriate tacrolimus doses to avoid overexposure.     

Association of CYP3A4*18B polymorphisms with the pharmacokinetics of cyclosporine in healthy subjects

The aim of this study is to evaluate the association of the CYP3A4*18B genotype with the cyclosporine metabolism in healthy subjects. We employed PCR–RFLP assays for analysis of the CYP3A4*18B genotype. Each of 26 subjects, comprising 12 CYP3A4*1/*1, 12 CYP3A4*1/*18B and 2 CYP3A4*18B/*18B, was given a single oral dose of cyclosporine (4?mg?kg^?1). The plasma concentrations of cyclosporine were measured for up to 24?h post dose by high-performance liquid chromatography–electrospray mass spectrometry. We found that the mean C_max (95% confidence intervals) of cyclosporine were 2237 (2905, 1859) (*1/*1), 2247 (2916, 1869) (*1/*18B), and 905 (1192, 506) ng?ml^?1 (*18B/*18B) (p?=?0.037) and the mean AUC0-4 were 5026 (6181, 4372) (*1/*1), 4434 (5481, 3841) (*1/*18B) and 2561 (3155, 1736) ng ml-1?h (*18B/*18B) (p?=?0.021). The CL in the *18B/*18B group was significantly higher than in the *1/*1 group. However, T_max exhibited no difference among the three genotypes. *18B/*18B group showed 50% reduction in concentration at 2?h post dose compared with *1/*18B (p?=?0.062) or *1/*1 (p?=?0.047), but no statistical significance was detected between*1/*1 and *1/*18B groups (p?>?0.05). The data suggest that the CYP3A4*18B genotype affects cyclosporine pharmacokinetics probably resulting from a higher enzymatic activity of this mutation in healthy subjects.     

Influence of ABCB1, CYP3A4*18B and CYP3A5*3 polymorphisms on cyclosporine A pharmacokinetics in bone marrow transplant recipients

The aim of this study was to retrospectively evaluate the effect of polymorphisms in the CYP3A4, CYP3A5 and ABCB1 genes on the dose-adjusted concentration and dose requirement of cyclosporine A (CsA) in Chinese recipients during the early period after bone marrow or hematopoietic stem cell transplantation. Ninety-one bone marrow transplant recipients were genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay or by direct sequencing for the C1236T, G2677T/A and C3435T polymorphisms in CYP3A4*18B, CYP3A5*3, and ABCB1, respectively. The concentration at zero before administration (C₀) and concentration at 2 h after administration (C₂) of whole blood CsA were measured by fluorescence polarization immunoassay. Dose-adjusted C₀ and C₂ were determined and compared among groups with different genotypes. Compared with CYP3A5*3/*3 individuals, CYP3A5*1/*1 subjects have a significantly lower dose-adjusted C₀ and C₂ at days 1–10 and a higher dose requirement for CsA at days 16–30 (p < 0.05). In addition, homozygotes for the ABCB1 3435T mutant have a significantly higher dose-adjusted C₀ and C₂ and a lower dose requirement compared with wildtype (p < 0.05). Similar results were also derived for carriers of the T-G-C haplotype in CYP3A5 producers compared with non-carriers (p < 0.05 and p < 0.01, respectively). In summary, the ABCB1 3435T SNP, T-G-C haplotype in CYP3A5 producers, and CYP3A5*3 SNP are all associated with differences in CsA pharmacokinetics and dose requirements during the first month after bone marrow or hematopoietic stem cell transplantation. Genetic testing can therefore help to determine initial dosage and individualize immunosuppressive therapy.     

Influence of pharmacogenetics on indinavir disposition and short-term response in HIV patients initiating HAART

Aims  To assess the relationship between genetic polymorphisms and indinavir pharmacokinetic variability and to study the link between concentrations and short-term response or metabolic safety. Methods  Forty protease inhibitor-naive patients initiating highly active antiretroviral therapy (HAART) including indinavir/ritonavir and enrolled in the COPHAR 2–ANRS 111 trial were studied. At week 2, four blood samples were taken before and up to 6 h following drug intake. A population pharmacokinetic analysis was performed using the stochastic approximation expectation maximization (SAEM) algorithm implemented in MONOLIX software. The area under the concentration–time curve (AUC) and maximum (C_max) and trough concentrations (C_trough) of indinavir were derived from the population model and tested for their correlation with short-term viral response and safety measurements, while for ritonavir, these same three parameters were tested for their correlation with short-term biochemical safety Results  A one-compartment model with first-order absorption and elimination best described both indinavir and ritonavir concentrations. For indinavir, the estimated clearance and volume of distribution were 22.2 L/h and 97.3 L, respectively. The eight patients with the *1B/*1B genotype for the CYP3A4 gene showed a 70% decrease in absorption compared to those with the *1A/*1B or *1A/*1A genotypes (0.5 vs. 2.1, P = 0.04, likelihood ratio test by permutation). The indinavir AUC and C_trough were positively correlated with the decrease in human immunodeficiency virus RNA between week 0 and week 2 (r = 0.4, P = 0.03 and r = -0.4, P = 0.03, respectively). Patients with the *1B/*1B genotype also had a significantly lower indinavir C_max (median 3.6, range 2.1–5.2 ng/mL) than those with the *1A/*1B or *1A/*1A genotypes (median 4.4, range 2.2–8.3 ng/mL) (P = 0.04) and a lower increase in triglycerides during the first 4 weeks of treatment (median 0.1, range −0.7 to 1.4 vs. median 0.6, range −0.5 to 1.7 mmol/L, respectively; P = 0.02). For ritonavir, the estimated clearance and volume of distribution were 8.3 L/h and 60.7 L, respectively, and concentrations were not found to be correlated to biochemical safety. Indinavir and ritonavir absorption rate constants were found to be correlated, as well as their apparent volumes of distribution and clearances, indicating correlated bioavailability of the two drugs. Conclusion  The CYP3A4*1B polymorphism was found to influence the pharmacokinetics of indinavir and, to some extent, the biochemical safety of indinavir.     

Pharmacogenomics of CYP2A6, CYP2B6, CYP2C19, CYP2D6, CYP3A4, CYP3A5 and MDR1 in Vietnam

Aim  The aim of this study was to obtain pharmacogenetic data in a Vietnamese population on genes coding for proteins involved in the elimination of drugs currently used for the treatment of malaria and human immunodeficiency virus/acquired immunodeficiency syndrome. Method  The main polymorphisms on the cytochrome P450 (CYP) genes, CYP2A6, CYP2B6, CYP2C19, CYP2D6, CYP3A4 and CYP3A5, and the multi-drug resistance 1 gene (MDR1) were genotyped in 78 healthy Vietnamese subjects. Pharmacokinetic metrics were available for CYP2A6 (coumarin), CYP2C19 (mephenytoin), CYP2D6 (metoprolol) and CYP3As (midazolam), allowing correlations with the determined genotype. Results  In the CYP2 family, we detected alleles CYP2A6*4 (12%) and *5 (15%); CYP2B6*4 (8%), *6 (27%); CYP2C19*2 (31%) and *3 (6%); CYP2D6*4, *5, *10 (1, 8 and 44%, respectively). In the CYP3A family, CYP3A4*1B was detected at a low frequency (2%), whereas CYP3A5 *3 was detected at a frequency of 67%. The MDR1 3435T allele was present with a prevalence of 40%. Allele proportions in our cohort were compared with those reported for other Asian populations. CYP2C19 genotypes were associated to the S-4′-OH-mephenytoin/S-mephenytoin ratio quantified in plasma 4 h after intake of 100 mg mephenytoin. While CYP2D6 genotypes were partially reflected by the α-OH-metroprolol/metoprolol ratio in plasma 4 h after dosing, no correlation existed between midazolam plasma concentrations 4 h post-dose and CYP3A genotypes. Conclusions  The Vietnamese subjects of our study cohort presented allele prevalences in drug-metabolising enzymes that were generally comparable with those reported in other Asian populations. Deviations were found for CYP2A6*4 compared to a Chinese population (12 vs. 5%, respectively; P = 0.023), CYP2A6*5 compared with a Korean population (15 vs. <1%, respectively; P < 0.0001), a Malaysian population (1%; P < 0.0001) and a Chinese population (1%; P < 0.0001); CYP2B6*6 compared with a Korean population (27 vs. 12%; P = 0.002) and a Japanese population (16%; P = 0.021). Pharmacokinetic metrics versus genotype analysis reinforces the view that the predictive value of certain globally common variants (e.g. CYP2D6 single nucleotide polymorphisms) should be evaluated in a population-specific manner.     

Effects of CYP3A4*1G and CYP3A5*3 polymorphisms on pharmacokinetics of tylerdipine hydrochloride in healthy Chinese subjects

1. The aim of this analysis was to explore the influence of CYP3A4*1G and CYP3A5*3 polymorphisms on the pharmacokinetics of tylerdipine in healthy Chinese subjects.

2. A total of 64 and 63 healthy Chinese subjects were included and identified as the genotypes of CYP3A4*1G and CYP3A5*3, respectively. Plasma samples were collected for up to 120?h post-dose to characterize the pharmacokinetic profile following single oral dose of the drug (5, 15, 20, 25 and 30?mg). Plasma levels were measured by a high-performance liquid chromatography-mass spectrometry (LC-MS/MS). The pharmacokinetic parameters were calculated using non-compartmental method. The maximum concentration (C_max) and the area under the curve (AUC_0–24?h) were all corrected by the dose given.

3. In the wild-type group, the mean dose-corrected AUC_0–24?h was 1.35-fold larger than in CYP3A4*1G carriers (p?=?.018). Among the three CYP3A5 genotypes, there showed significantly difference (p?=?.008) in the t_1/2, but no significant difference was observed for the AUC_0–24?h and C_max. In subjects with the CYP3A5*3/*3 genotype, the mean t_1/2 was 1.35-fold higher than in CYP3A5*1/*1 group (p?=?.007). And the t_1/2 in CYP3A5*3 carriers also was 1.32-fold higher than in the wild-type group (p?=?.004).

4. CYP3A4*1G and CYP3A5*3 polymorphisms may influence tylerdipine pharmacokinetic in healthy Chinese subjects.

     

Effects of genetic polymorphisms of CYP3A4, CYP3A5 and MDR1 on cyclosporine pharmacokinetics after renal transplantation

1. The calcineurin inhibitor cyclosporine is widely used to prevent allograft rejection after solid organ transplantation. It has a narrow therapeutic index and shows considerable interindividual differences in its pharmacokinetics. Interindividual differences in the activity and expression of the metabolising enzymes cytochrome P450 (CYP) 3A4 and 3A5 and the multidrug efflux pump P-glycoprotein (P-gp) contribute considerably to cyclosporine pharmacokinetics. Variability in the activity of CYP3A4, CYP3A5 and P-gp could be considered to result from genetic polymorphisms encoding their genes. 2. The aim of the present study was to evaluate retrospectively the effects of genetic polymorphisms of CYP3A4, CYP3A5 and MDR1 on cyclosporine dose adjusted trough blood concentration during the early period after renal transplantation in Chinese patients. 3. One hundred and six renal transplant recipients in China were genotyped by polymerase chain reaction-restriction fragment length polymorphism for CYP3A4*18A, CYP3A5*3 and MDR1 C3435T. Cyclosporine whole blood levels were measured by fluorescence polarization immunoassay. Dose-adjusted trough blood concentrations (C(0)) were determined and compared among the different genotype groups. 4. The frequency of the CYP3A4*18A, CYP3A5*3 and MDR1 C3435T variant alleles were 0.005 (95% confidence interval (CI) 0.048, 0.0049), 0.783 (95% CI 0.781, 0.785) and 0.528 (95% CI 0.526, 0.531), respectively, and these alleles exhibited incomplete linkage disequilibrium. The median cyclosporine dose-adjusted C(0) in CYP3A5*1/*1 genotype subjects (n = 6) was 14.8 ng/mL per mg per kg (range 11.1-26.8 ng/mL per mg per kg), in CYP3A5*1/*3 patients (n = 34) it was 23.7 ng/mL per mg per kg (range 9.0-61.0 ng/mL per mg per kg) and for CYP3A5*3/*3 patients (n = 66) it was 26.4 ng/mL per mg per kg (range 9.8-85.8 ng/mL per mg per kg; P = 0.012, Kruskal-Wallis test). Accordingly, cyclosporine dose-adjusted C0 was larger in CYP3A5 non-expressors than expressors in the first week after renal transplantation. In addition, wild-type homozygotes (n = 21) for MDR1 C3435T had a slight but significantly lower dose-adjusted C0 compared with heterozygotes (n = 58): 17.7 (10.3-60.8) versus 26.4 (9.0-67.3) ng/mL per mg per kg, respectively (P = 0.014, Mann-Whitney U-test). 5. In conclusion, the present study shows that genetic polymorphisms in CYP3A5 may be responsible, in part, for the large interindividual variability of cyclosporine pharmacokinetics during the early phase after renal transplantation in Chinese patients. Patients with the CYP3A5*3 variant genotype require a low dose of cyclosporine to reach target levels compared with those with the CYP3A5*1 allele.     

Influence of the MDR1 haplotype and CYP3A5 genotypes on cyclosporine blood level in Chinese renal transplant recipients

1. The purpose of the study was to elucidate the influence of multidrug resistance gene (MDR1) haplotype and CYP3A5 genotype on cyclosporine (CsA) blood level in Chinese renal transplant recipients.

2. CsA trough level (C₀) and peak level (C₂) of 115 patients 1 week and 1 month after renal transplantation were determined. MDR1 C1236T, G2677T/A, C3435T and CYP3A5*3 genotypes were determined by polymerase chain reaction (PCR) assays based on amplification refractory mutation.

3. Dose-adjusted C₀ (C₀/D), C₂ (C₂/D) were 50.5?±?22.5, 267.8?±?110.1 ng·kg·(ml·mg)^?1 after 1 week of therapy, and 79.3?±?29.4, 406.0?±?135.3 ng·kg·(ml·mg)^?1 after 1 month of therapy. Frequencies of MDR1 haplotype TTT, CGC, and TGC were 27.0%, 25.2% and 20.0%, respectively. After 1 month of therapy, C₂/D of TTT/TTT patients were 30% (p = 0.057) and 53% (p = 0.003) higher than CGC/TTT and CGC/CGC patients. C₀/D of CYP3A5 *1/*1, *1/*3 and *3/*3 patients after 1 month of therapy were 51.8?±?25.0, 71.5?±?27.6, and 86.7?±?28.6 ng·kg·(ml·mg)^?1 (p < 0.05).

4. MDR1 haplotypes and CYP3A5*3 genotypes can be related to C₂ and C₀ of CsA, respectively.

     

Influence of CYP3A5 genetic polymorphism on cyclosporine A metabolism and elimination in Chinese renal transplant recipients

AIM: To investigate whether the CYP3A5*3 polymorphism would affect cyclosporine A (CsA) metabolism in Chinese renal transplant patients. METHODS: The CYP3A5*3 genotype was determined in Chinese renal transplant recipients using polymerase chain reaction and amplification of specific alleles (PCR-ASA). The concentrations of CsA and metabolites were separately measured by fluorescence polarization immunoassay and dose-adjusted trough concentrations and metabolic ratio (MR) values were calculated. RESULTS: The trough concentrations adjusted with the dose was significantly higher in the wild allele carriers compared to both the homozygous (*3*3) and heterozygous variants (*1*3). However, no significant difference was found for the dose-adjusted metabolite concentrations. The MR values for the 3 genotype groups were as follows: 0.92+/-0.62 for CYP3A5*3/ *3 (n=14), 0.99+/-0.51 for CYP3A5*1/*3 (n=15), and 1.45+/-0.62 for CYP3A5*1/*1 (n=9), respectively. Post hoc comparisons showed that only the MR values between the CYP3A5*3/*3 group and the CYP3A5*1/*1 group were significantly different. CONCLUSION: The CYP3A5*3 polymorphism exerted little effect on cyclosporine metabolism. The MR may be a more accurate indicator for therapeutic drug monitoring, considering its integrated information on body exposure of both parent drugs and metabolites.     

CYP2C19 genotypes and omeprazole metabolism after single and repeated dosing when combined with clarithromycin

Objectives: Omeprazole is metabolized mainly by CYP2C19 which has two major mutations (CYP2C19*2 in exon5 and CYP2C19*3 in exon4) associated with the poor metabolizer (PM) phenotype. The aim of this study was to examine the relationship between genetic polymorphism of CYP2C19 and metabolism of omeprazole administrated as a single dose or as repeated-doses, which were in both cases co-administered with clarithromycin. Methods: Twelve healthy Japanese subjects were typed for CYP2C19 polymorphism. In the single-dose study, plasma levels of omeprazole and its metabolites were measured for 24 h after administration of 20 mg omeprazole and 400 mg clarithromycin to six healthy Japanese subjects. In the repeated-dose study, plasma levels of omeprazole and its metabolites were measured after repeated oral administration of 20 mg omeprazole and 400 mg clarithromycin twice daily for 6 days and then after 20 mg omeprazole and 400 mg clarithromycin once on the 7th day to the other 6 healthy Japanese subjects. Results: In the single-dose study, the areas under the plasma concentration-versus-time curve (AUCs) of omeprazole of homozygotes for the wild-type allele (*1/*1 n = 2), heterozygotes (n = 3) for the CYP2C19*2 (*1/*2) or for the CYP2C19*3 (*1/*3) and heterozygote (n = 1) for the two defects (*2/*3) were on average 450, 1007 and 6710 ng · h⁻¹ · ml⁻¹, respectively. The ratios of AUCs of omeprazole/5-hydroxyomeprazole for *1/*1, *1/*2 or *1/*3 and *2/*3 were 1, 2 and 30, respectively. In the repeated-dose study, the AUCs of omeprazole for *1/*1, *1/*2 or *1/*3 and *2/*3 were 4041 (n = 2), 3149 (n = 3) and 6684 (n = 1) ng · h⁻¹ · ml⁻¹, respectively. The ratios of AUCs of omeprazole/5-hydroxyomeprazole for *1/*1, *1/*2 or *1/*3 and *2/*3 were 7, 11 and 30, respectively. In the repeated-dose study, the AUC of omeprazole of *1/*1 genotypes was nine-fold higher, that of *1/*2 and *1/*3 genotypes was three-fold higher, and the C_max value of omeprazole was three-fold higher compared with subjects with the same genotype in the single-dose study. However, there were few differences in the AUC and C_max of omeprazole between the *2/*3 genotype in the single-dose study and the homozygote for the CYP2C19*2 (*2/*2) in the repeated-dose study. Conclusion: Subjects with *1/*1, *1/*2 and *1/*3 genotypes in the repeated-dose study had lower CYP2C19 activity than subjects of the same genotype in the single-dose study. The difference in omeprazole metabolism between subjects with different genotypes observed on day 1 seemed to disappear after 7 days of repeated-dose administration. Received: 5 June 1998 / Accepted in revised form: 27 October 1998     

Association of CYP3A polymorphisms with the pharmacokinetics of cyclosporine A in early post-renal transplant recipients in China

Aim:

To evaluate retrospectively the association of cytochrome P450 3A (CYP3A) and ATP-binding cassette sub-family B member 1 (ABCB1) gene polymorphisms with the pharmacokinetics of cyclosporine A (CsA) in Chinese renal transplant patients.

Methods:

One hundred and twenty-six renal transplant patients were recruited. Blood samples were collected, and corresponding clinical indices were recorded on the seventh day after the procedure. The patients were genotyped for CYP3A4*1G, CYP3A5*3C, ABCB1 1236 C>T, ABCB1 2677 G>T/A, and ABCB1 3435 C>T polymorphisms. Whole blood trough concentrations of CsA at time zero (C₀) were measured before the drug administration. A multiple regression model was developed to analyze the effects of genetic factors on the CsA dose-adjusted C₀ (C₀/dose) based on several clinical indices.

Results:

The CYP3A5*3C polymorphism influenced the C₀ and C₀/dose of CsA, which were significantly higher in patients with the GG genotype than in patients with the AA or GA genotypes. No significant differences were detected for other SNPs (CYP3A4*1G, ABCB1 1236 C>T, ABCB1 2677 G>T/A, and ABCB1 3435 C>T). In a univariate analysis using Pearson''s correlation test, age, hemoglobin, blood urea nitrogen and blood creatinine levels were significantly correlated with the log-transformed CsA C₀/dose. In the multiple regression model, CYP3A5*3C, age, hemoglobin and blood creatinine level were associated with the log-transformed CsA C₀/dose.

Conclusion:

CYP3A5*3C correlates with the C₀/dose of CsA on the seventh day after renal transplantation. The allele is a putative indicator for the optimal CsA dosage in the early phase of renal transplantation in the Chinese population.     

Lack of differences in diclofenac (a substrate for CYP2C9) pharmacokinetics in healthy volunteers with respect to the single CYP2C9 * 3 allele

Objectives: Evidence exists to suggest that diclofenac is metabolised by CYP2C9. The present study was undertaken in order to evaluate the effect of the single CYP2C9*3 variant on drug metabolism using diclofenac as a probe drug. Methods: A single dose of diclofenac was administered orally to 12 healthy subjects in whom the genotype of CYP2C9 had been determined previously. The disposition kinetics of diclofenac were compared between homozygotes for the wild type (CYP2C9*1/*1, n=6) and heterozygotes for the Leu359 variant (CYP2C9*1/*3, n=6). Results: For diclofenac, the following kinetic parameters were observed in the CYP2C9*1/*1 and CYP2C9*1/*3 subjects, respectively (mean ± SD): apparent oral clearance (ml/kg/h) 355.8 ± 56.9 and 484.4 ± 155.3; area under plasma concentration–time curve (μg h/ml) 2.7 ± 0.7 and 1.9 ± 0.6. The formation clearance of 4′-hydroxydiclofenac (ml/kg/h) was 63.6 ± 19.1 in the CYP2C9*1/*1 subjects compared with 75.9 ± 27.6 in the CYP2C9*1/*3 subjects. There were no significant differences in any of the kinetic parameters for either diclofenac disposition or formation clearance of 4′-hydroxydiclofenac between the two genotype groups. Conclusion: Since the disposition kinetics of diclofenac does not change in subjects with the single CYP2C9*3 mutant allele, it is suggested that the effects of CYP2C9 polymorphisms on the drug metabolism tend to be substrate specific. Received: 4 October 1999 / Accepted in revised form: 12 January 2000     

<Emphasis Type="Italic">CYP3A5 *1</Emphasis> allele associated with tacrolimus trough concentrations but not subclinical acute rejection or chronic allograft nephropathy in Japanese renal transplant recipients

Purpose  We assessed reported associations of CYP3A5 *1 allele with a delay in achieving target tacrolimus concentrations, and occurrence of biopsy-confirmed subclinical acute rejection (SAR) and chronic allograft nephropathy (CAN) in Japanese subjects. Methods  Forty-one renal allograft recipients were studied. The targeted tacrolimus trough concentrations were 20–25 ng/mL up to 2 weeks post-transplantation, 10–15 ng/mL up to 6 weeks, and 5–10 ng/mL thereafter. At 1 month and 1 year post-transplantation, allograft biopsies were performed. Results  The CYP3A5 *1/*1 + *1/*3 (expresser) and *3/*3 (nonexpresser) alleles were detected in 19 and 22 patients, respectively. Although the mean trough concentrations were lower in CYP3A5 expressers than nonexpressers for the first 3 weeks, no difference in frequency of SAR among CYP3A5 genotypes was found. The mean trough concentrations were lower from 8 to 12 months post-transplantation, and the frequency of CAN was lower in CYP3A5 expressers. Conclusions  In contrast to the previous reports, the CYP3A5 *1 allele was not associated with the frequency of SAR or CAN, suggesting that further studies of different immunosuppressive strategies using tacrolimus are needed to confirm the adequate dosing and concentration of tacrolimus for each CYP3A5 genotype.