Influence of ABCB1 genetic polymorphisms on cyclosporine intracellular concentration in transplant recipients

OBJECTIVE: The expression on lymphocytes of P-glycoprotein, an efflux transporter encoded by the ABCB1 gene, might influence cyclosporine intracellular concentration. METHODS: ABCB1 genotypes, cyclosporine intracellular and blood concentrations were determined in 64 stable renal, liver or lung transplant recipients. RESULTS: Cyclosporine intracellular concentration correlated moderately with blood concentration (r=0.30, P<0.00005). The ABCB1 1199A carriers presented a 1.8-fold decreased cyclosporine intracellular concentration (P=0.04), whereas the 3435T carriers presented a 1.7-fold increase (P=0.02) as well as a 1.2-fold increased blood concentration (P=0.04). In contrast, ABCB1 61A>G, 1236C>T and 2677G>T polymorphisms did not influence cyclosporine intracellular and blood concentrations. CONCLUSION: This is the first report demonstrating that ABCB1 polymorphisms influence cyclosporine intracellular concentration. Interestingly, its influence on intracellular concentration is significantly higher than on blood concentration (P<0.002). This may therefore modulate cyclosporine immunosuppressive activity.     

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.     

Association study of ABCB1 and CYP3A5 gene polymorphisms with sirolimus trough concentration and dose requirements in Chinese renal transplant recipients

The objective of this study was to investigate the possible association of the ABCB1 gene C3435 T polymorphism and the CYP3A5 gene A6986G polymorphism with sirolimus (SRL) trough concentration and dose requirements in Chinese stable renal transplant recipients. Blood samples were collected from 105 healthy volunteers and 50 renal transplant patients, whose polymorphisms of the ABCB1 and CYP3A5 genes were determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). Plasma concentrations of SRL were determined with HPLC. The allele frequencies of the ABCB1 mutation in Chinese healthy volunteers and renal transplant recipients were 51.0% and 44.0% (p>0.05), while the allele frequencies of the CYP3A5 mutation were 72.9% and 71.0% (p>0.05). The SRL concentration/dose ratio (C/D) in patients with CYP3A5 (*)3/(*)3 were significantly higher than that of those with (*)1 allele (p<0.05). However, no significant differences were observed between C/D and ABCB1 SNPs (p>0.05). These results confirm that when treated with a SRL-based therapy and low-dose steroids, patients carrying the CYP3A5(*)1 allele required significantly more SRL to achieve adequate blood trough concentrations. In patients with SRL-based therapy, genotyping of the CYP3A5 genes may help to optimize the SRL management in renal transplant recipients.     

回顾性研究细胞色素P4503A5基因多态性对肾移植病人环孢素浓度的影响

目的 回顾性研究稳定期肾移植的病人在合用地尔硫卓后,CYP3A5基因多态性对环孢素(免疫抑制剂)浓度的影响.方法 用RFLP-PCR检测CYP3A5基因型;采用回顾性研究方法,分析肾移植病人CYP3A5基因型与环孢素血药浓度的关系.结果 合用地尔硫卓的病人,按CYP3A5不同基因型分组,3组病人之间的环孢素剂量和剂量调整浓度有明显差异;而不用地尔硫卓的病人进行分组后,环孢素剂量调整浓度也存在显著差异;环孢素剂量调整浓度,CYP3A5表达者显著低于不表达者组.结论 CYP3A5基因型对稳定期肾移植病人环孢素药代动力学有显著影响,且此相关性不受合用地尔硫卓影响.     

肝移植患者他克莫司血药浓度与细胞色素P450 3A5 1*3基因多态性的关系

目的研究细胞色素P450 3A5 1*3基因多态性对肝移植患者他克莫司(免疫抑制剂)血药浓度的影响,探讨他克莫司在不同个体间吸收、代谢差异的基因背景。方法观察150例肝移植术后常规使用他克莫司 吗替麦考酚酯胶囊 醋酸泼尼松三联免疫抑制治疗的成年患者,分别测定术后1、3、6个月和12月的他克莫司全血药浓度,采用等位基因特异PCR测定细胞色素P450 3A5 1*3基因多态性,比较不同基因型之间他克莫司的浓度/剂量比的差异。结果在口服相同剂量的他克莫司时,1个月内CYP3A5 1*1、CYP3A5 1*3和CYP3A5 3*3三种基因型的浓度/剂量比,差异不显著;但3个月后,差异显著;6个月和12个月的浓度/剂量比,差异非常显著。结论CYP3A5 1*3多态性与肝移植患者他克莫司血药浓度具有非常显著的相关性,携带等位基因1*1和1*3患者的血药浓度明显低于3*3纯合子患者。     

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.     

Association of MDR1, CYP3A4*18B, and CYP3A5*3 polymorphisms with cyclosporine pharmacokinetics in Chinese renal transplant recipients

Objective  The objective of this study was to retrospectively evaluate the effects of MDR1, CYP3A4*18B, and CYP3A5*3 genetic polymorphisms on cyclosporine A (CsA) pharmacokinetics in Chinese renal transplant patients during the first month after transplantation. Methods  A total of 103 renal transplant recipients receiving CsA were genotyped for MDR1 (C1236T, G2677T/A, and C3435T), CYP3A4*18B, and CYP3A5*3. The predose and 2-h postdose concentrations of CsA (C₀ and C₂, respectively) were determined by fluorescence polarization immunoassay, and their relationships with corresponding genotypes and haplotypes were investigated. Results  Patients with a CYP3A4*1/*1 genotype were found to have a higher dose-adjusted concentration compared with those with CYP3A4*18B/*18B, as follows: for C₂, 19.3% (P = 0.008) during days 8-15, 35.2% (P = 0.008) during days 16–30, and for C₀, 39.7% (P = 0.012) during days 16–30. The dose-adjusted C₀ was higher in patients with MDR1 1236CC compared with those with 1236TT in the first month postoperation. The dose-adjusted C₀ in patients with the CYP3A5*3/*3 genotype was 25.5% and 30.7% higher than those with the wild-type genotype during days 8–15 (P = 0.011) and days 16–30 (P = 0.015), respectively. Haplotype analysis revealed that the dose-adjusted C₀ was higher in the first month following surgery in carriers of haplotype MDR1 CAC than in noncarriers. Polymorphisms of MDR1 and CYP3A5*3 did not affect dose-adjusted C_2. Conclusion  The data suggests that the CYP3A4*18B genotype affects CsA pharmacokinetics during the first month following surgery in Chinese renal transplant recipients. Patients with CYP3A4*18B alleles may require higher doses of CsA to reach the target levels. Large prospective studies may be needed to further explore the impact of MDR1 and CYP3A5*3 polymorphisms on CsA pharmacokinetics in renal transplant recipients.     

Associations of ABCB1, NFKB1, CYP3A,and NR1I2 polymorphisms with cyclosporine trough concentrations in Chinese renal transplant recipients

Aim:

Cyclosporine requires close therapeutic drug monitoring because of its narrow therapeutic index and marked inter-individual pharmacokinetic variation. In this study, we investigated the associations of CYP3A4, CYP3A5, ABCB1, NFKB1, and NR1I2 polymorphisms with cyclosporine concentrations in Chinese renal transplant recipients in the early period after renal transplantation.

Methods:

A total of 101 renal transplant recipients receiving cyclosporine were genotyped for CYP3A4^*1G, CYP3A5^*3, ABCB1 C1236T, G2677T/A, C3435T, NFKB1 −94 ins/del ATTG, and NR1I2 polymorphisms. Cyclosporine whole blood levels were measured by a fluorescence polarization immunoassay. Trough concentrations of cyclosporine were determined for days 7-18 following transplantation.

Results:

The dose-adjusted trough concentration (C₀) of cyclosporine in ABCB1 2677 TT carriers was significantly higher than that in GG carriers together with GT carriers [90.4±24.5 vs 67.8±26.8 (ng/mL)/(mg/kg), P=0.001]. ABCB1 3435 TT carriers had a significantly higher dose-adjusted C₀ of cyclosporine than CC carriers together with CT carriers [92.0±24.0 vs 68.4±26.5 (ng/mL)/(mg/kg), P=0.002]. Carriers of the ABCB1 1236TT-2677TT-3435TT haplotype had a considerably higher CsA C₀/D than carriers of other genotypes [97.2±21.8 vs 68.7±26.9 (ng/mL)/(mg/kg), P=0.001]. Among non-carriers of the ABCB1 2677 TT and 3435 TT genotypes, patients with the NFKB1 −94 ATTG ins/ins genotype had a significantly higher dose-adjusted C₀ than those with the −94 ATTG del/del genotype [75.9±32.9 vs 55.1±15.1 (ng/mL)/(mg/kg), P=0.026].

Conclusion:

These results illustrate that the ABCB1 and NFKB1 genotypes are closely correlated with cyclosporine trough concentrations, suggesting that these SNPs are useful for determining the appropriate dose of cyclosporine.     

CYP3A4,CYP3A5和MDR1基因多态性对环孢素处置的影响

环孢素是一个广泛用于器官移植患者的免疫抑制剂,具有治疗指数窄,不同个体间药代动力学差异较大的特点。它主要通过肝脏和小肠的CYP3A4和CYP3A5代谢;同时它又是药物转运体的底物。不同个体间药物代谢酶和转运体活性的差异可能是造成不同器官移植患者环孢素药代动力学差异的主要原因。而遗传因素即编码药物代谢酶和转运体基因序列的差异可能是其产生活性差异的分子机制。因此,从编码药物代谢酶和转运体的基因入手,可能会为器官移植患者提供最优的治疗方案。     

CYP3A基因多态性与心脏移植术后环孢素肾毒性的相关性

目的：探讨心脏移植受者CYP3A基因多态性与环孢素（CsA）所致肾毒性易感性的关系。方法：应用飞行时间质谱技术分析66例CsA免疫抑制治疗发生肾毒性（20例）和未发生肾毒性（46例）心脏移植术后患者的CYP3A基因多态性,并通过统计学分析CYP3A各单核苷酸多态性（SNP）位点基因型与CsA所致肾毒性之间的关系。结果：筛选出8个标签位点的等位基因在肾毒性和非肾毒性组间的分布差异均无统计学意义。经非条件性二元Logistic回归分析,在AIC定义的共显性和显性遗传模型下,未发现CYP3A基因8个SNP位点与CsA肾毒性的发生有显著性关联。结论：本研究显示心脏移植受者本次调查的CYP3A基因位点与CsA所致肾毒性无显著性关联。     

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。     

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.     

肾移植病人中CYP3A4基因多态性对环孢素A代谢的影响

目的 用基因分析技术对CsA代谢酶CYP3A4进行基因分型,以阐述CYP3A4基因多态性对环孢素A代谢的影响及相互关系,从而预测血药浓度及安全性。方法 用聚合酶链反应结合限制性片段长度多态性分析法分别建立了CYP3A的CYP3A4基因亚型3个新突变点(CYP3A4~*4,~*5,~*6)的基因分型方法,并对中国肾移植人群进行基因分型,同时测定CsA及其代谢物浓度,以原形药与代谢物浓度的比值MR作为表型验证指标。结果CYP3A4~*4,*~5,*~6等位基因在中国肾移植人群中的突变率为:2/133,3/197,3/200。野生型病人中肝肾功能正常和异常者测得MR均值分别为0.47±0.13和0.82±0.21。3种突变型病人MR均值为0.90±0.30。结论CYP3A4~*4,~*5,~*6等位基因的存在有可能降低了药物代谢酶CYP3A4的活性,从而使环孢素A的代谢减慢。     

The effect of CYP3A5 and MDR1 (ABCB1) polymorphisms on cyclosporine and tacrolimus dose requirements and trough blood levels in stable renal transplant patients

Cyclosporine and tacrolimus are immunosuppressive drugs largely used in renal transplantation. They are characterized by a wide inter-individual variability in their pharmacokinetics with a potential impact on their therapeutic efficacy or induced toxicity. CYP3A5 and P-glycoprotein appear as important determinants of the metabolism of these drugs. The objective of this study was to investigate the effect of CYP3A5 and MDR1 (ABCB1) polymorphisms on cyclosporine and tacrolimus dose requirements and trough blood concentrations in stable transplant patients. Stable renal transplant recipients receiving cyclosporine (n = 50) or tacrolimus (n = 50) were genotyped for CYP3A5*3 and *6, and MDR1 C1236T, G2677T/A and C3435T. Dose-adjusted trough blood levels (ng/ml per mg/kg body weight) as well as doses (mg/kg body weight) required to achieve target blood concentrations were compared among patients according to allelic status for CYP3A5 and MDR1. Dose-adjusted trough concentrations were three-fold and 1.6-fold higher in CYP3A5*3/*3 patients than in CYP3A5*1/*3 patients for tacrolimus and cyclosporine, respectively. In the case of tacrolimus, the difference was even more striking when considering CYP3A5*1/*1 patients showing dose-adjusted trough concentrations 5.8-fold lower than CYP3A5*3/*3 patients. For both drugs, no association was found between trough blood concentrations or dose requirement and MDR1 genotype. Multiple regression analyses showed that CYP3A5*1/*3 polymorphism explained up to 45% of the variability in dose requirement in relation to tacrolimus use. Given the importance of rapidly achieving target blood concentrations after transplantation, further prospective studies should consider the immediate post-graft period and assess the influence of this specific polymorphism. Beside non-genetic factors (e.g. steroids dosing, drugs interactions), CYP3A5 pharmacogenetic testing performed just before transplantation could contribute to a better individualization of immunosuppressive therapy.     

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.     

PXR基因多态性与心脏移植术后稳定期环孢素血药浓度的相关性

目的：探讨心脏移植患者术后口服免疫抑制剂环孢素的血药浓度与PXR基因多态性的相关性。方法：应用飞行时间质谱技术对59例心脏移植术后稳定期患者的PXR基因型进行检测,全自动化学免疫分析仪测定环孢素的血药浓度,并通过统计学分析PXR各单核苷酸多态性（SNP）位点基因型对环孢素血药浓度的影响。结果：PXR基因筛选出的8个Tag SNP位点次要等位基因频率（MAF）与NCBI的dbSNP数据库中中国人的数据相近。对于59名稳定期心脏移植患者PXR基因8个Tag SNP中,仅携带PXR rs1523127（C 24381 A）位点AA型基因的患者血药浓度及校正血药浓度明显低于CA型,CA型又低于CC型患者,差异均具有统计学意义（P＜0.05）。其他7个Tag SNP rs3814056T＞G、rs7643645A＞G、rs11917714C＞T、rs2276705C＞A、rs2472681T＞C、rs2472682C＞A、rs4440154C＞T各基因型组间环孢素血药浓度的差异均无统计学意义。结论：PXR rs1523127（C 24381 A）基因型与心脏移植稳定期患者环孢素血药浓度显著相关,提示该SNP可能会在环孢素个体化用药中发挥重要作用。     

Frequencies and roles of CYP3A5, CYP3A4 and ABCB1 single nucleotide polymorphisms in Italian teenagers after kidney transplantation

The main genes involved in the pharmacokinetics of immunosuppressive drugs are those encoding cytochrome P450 (CYP) family enzymes and multidrug resistance 1 (ABCB1). In this study, 87 Italian teenagers with transplanted kidneys (mean age 11.6 ± 4.8 years) receiving calcineurin inhibitors (CNIs) were genotyped for the single nucleotide polymorphisms (SNPs) CYP3A5*1/3 and CYP3A4*1B for CYP3A, and C1236T, G2677T/A, C3435T and IVS21+49 for ABCB1, and retrospectively evaluated for the influence of the screened SNPs on CNI blood level at different post-transplantation times. The CYP3A5*1 allele was present in 7% of the patients, and the CYP3A4*1B allele was present in 3% of patients. The ABCB1 C1236T, G2677T/A and C3435T SNPs C, G and T occurred frequently (55%, 53% and 54%, respectively). The frequency of the T allele of IVS21+49 was 86%. The frequency of SNPs in both genes was comparable with that reported in other European Caucasian populations but different from that found in Asians or Afro-Americans. None of the cyclosporine (CsA) pharmacokinetic parameters were associated with the CYP3A5 genetic polymorphism, whereas the presence of the A allele in some patients was responsible for the required administration of a significantly increased dose of tacrolimus (Tac) that was necessary to reach therapeutic target levels. None of the Tac pharmacokinetic parameters were associated with ABCB1 SNPs, but ABCB1 SNPs had early effects on the CsA exposure index and dose requirements. In conclusion, because SNPs of the CYP3A and ABCB1 genes may be associated with CNI pharmacokinetic parameters and exposure indices, pre-transplant genetic screening should be considered in order to avoid immunosuppressant-related adverse events.     

Genetic polymorphisms of the CYP3A4, CYP3A5, CYP3A7 and CYP1A2 among the Jordanian population

Cytochromes P450 (CYP450) plays an extremely vital role in oxidation, reduction, and peroxidation of numerous endogenous and exogenous compounds, like drugs and procarcinogens. Mainly, expression occurs in the liver, in varying polymorphic forms. Therefore, proposed as biomarkers of susceptibility to carcinogenicity and toxicity. The objective of this study was to find the allelic frequencies of CYP3A5*2,*3,*4,*5,*6,*7, CYP3A4*1B, CYP3A7*1C and CYP1A2*1C, *1D, *1E, *1F enzymes in Jordanians, and to compare them with other ethnic groups. We used polymerase chain reaction-restriction fragment length (PCR-RFLP) to genotype alleles, and we calculated frequencies using Hardy Weinberg's equation (HWE). Allelic frequencies results were: CYP3A5*2 (0.2%), CYP3A5*3 (86.6%), CYP3A5*6 (1.7%), CYP*3A5*4,*5*7 not detected, CYP3A4*1B (11.7%), CYP3A7*1C (1.7%). Finally 6.5%, 18.2%, 6.0%, 67.3% were the results of CYP1A2*1C, 1D, 1E and 1F, respectively. In conclusion, genotyping method and results of this study can be adopted or used in pharmacotherapy, toxicity and carcinogenic studies in Jordan.     

Population pharmacokinetic analysis of cilostazol in healthy subjects with genetic polymorphisms of CYP3A5, CYP2C19 and ABCB1

AIMS

To investigate the influence of genetic polymorphisms in the CYP3A5, CYP2C19 and ABCB1 genes on the population pharmacokinetics of cilostazol in healthy subjects.

METHODS

Subjects who participated in four separate cilostazol bioequivalence studies with the same protocols were included in this retrospective analysis. One hundred and four healthy Korean volunteers were orally administered a single 50- or 100-mg dose of cilostazol. We estimated the population pharmacokinetics of cilostazol using a nonlinear mixed effects modelling (nonmem) method and explored the possible influence of genetic polymorphisms in CYP3A (CYP3A5*3), CYP2C19 (CYP2C19*2 and CYP2C19*3) and ABCB1 (C1236T, G2677T/A and C3435T) on the population pharmacokinetics of cilostazol.

RESULTS

A two-compartment model with a first-order absorption and lag time described the cilostazol serum concentrations well. The apparent oral clearance (CL/F) was estimated to be 12.8 l h⁻¹. The volumes of the central and the peripheral compartment were characterized as 20.5 l and 73.1 l, respectively. Intercompartmental clearance was estimated at 5.6 l h⁻¹. Absorption rate constant was estimated at 0.24 h⁻¹ and lag time was predicted at 0.57 h. The genetic polymorphisms of CYP3A5 had a significant (P < 0.001) influence on the CL/F of cilostazol. When CYP2C19 was evaluated, a significant difference (P < 0.01) was observed among the three genotypes (extensive metabolizers, intermediate metabolizers and poor metabolizers) for the CL/F. In addition, a combination of CYP3A5 and CYP2C19 genotypes was found to be associated with a significant difference (P < 0.005) in the CL/F. When including these genotypes, the interindividual variability of the CL/F was reduced from 34.1% in the base model to 27.3% in the final model. However, no significant differences between the ABCB1 genotypes and cilostazol pharmacokinetic parameters were observed.

CONCLUSIONS

The results of the present study indicate that CYP3A5 and CYP2C19 polymorphisms explain the substantial interindividual variability that occurs in the metabolism of cilostazol.