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Effects of CYP3A5 Genetic Polymorphism on the Pharmacokinetics of Tacrolimus in Renal Transplant Recipients
Effects of CYP3A5 Genetic Polymorphism on the Pharmacokinetics of Tacrolimus in Renal Transplant Recipients R. Mac Guada, N.L. Zaharana, Z. Chika, Z. Mohameda, N.K. Pengb, and W.A.H.W.M. Adnanb,* a Department of Pharmacology, and bDivision of Nephrology, Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
ABSTRACT Background. The aim of this study was to compare the within-patient variability trough levels (Co), dose-adjusted Co, and dose requirements of Prograf and Advograf with CYP3A5 polymorphisms in Malaysia renal transplant recipients. Methods. Stable posterenal transplantation patients switched from Prograf to Advograf were retrospectively identified from University Malaya Medical Centre (n ¼ 28). Co and concomitant tacrolimus dose 6 months preconversion and postconversion were examined. CYP3A5 was genotyped using reverse transcriptase polymerase chain reaction. Wilcoxon signed rank test and Mann-Whitney U test were used to compare Co and dose between formulations and according to genotypes. Results. There was a significant difference in the whole-blood tacrolimus Co between the 2 groups (6.16 1.74 ng/mL vs 4.90 1.06 ng/mL; P ¼ .0001). The mean daily maintenance dose of Prograf was 3.9 2.0 mg/kg (0.06 mg/kg/d), which was reduced to 3.3 1.7 mg/d (0.04 mg/kg/d) with Advograf (P ¼ .01). The mean maintenance dose of tacrolimus required for those with CYP3A5*1/*1 (high-expressive) was significantly higher than those with CYP3A5*1/*3 (intermediate-expressive) and CYP3A5*3/*3 (lowexpressive) (P < .01) for both formulations. Comparing those with CYP3A5*1/*1, the average dose-adjusted Co was significantly higher in patients with CYP3A5*3/*3 with Advograf (P < .05). Conclusions. The requirement for daily maintenance dose was higher in those with CYP3A5*1/*1 variants in both tacrolimus formulations in the Malaysian patients. Furthermore, those with CYP3A5*3/*3 demonstrated significantly higher dose-adjusted Co with Advograf.
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INCE the approval of tacrolimus by the U.S. Food and Drug Administration (FDA) in April 1994 for allogenic liver transplant recipients, it has emerged as an alternative to cyclosporine in renal transplantation for the prevention of allograft rejection. In fact, currently more than two thirds of all renal transplant recipients are prescribed tacrolimus as part of their immunosuppressant regimen [1]. One of the drawbacks of tacrolimus is its wide within-patient and interpatient variabilities [2], which lead to this drug having a narrow therapeutic index [3]. In addition, for more than 10 years, oral tacrolimus has only been available as a standard twice-daily formulation manufactured by Astellas Pharma Europe Ltd (Staines, United Kingdom) as Prograf. As in the case of any drugs that have ª 2016 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
Transplantation Proceedings, 48, 81e87 (2016)
to be consumed multiple times daily, adherence to medication is a recognized challenge [4]. A newer, prolonged-release formulation of tacrolimus (Advograf), which only needs to be taken once-daily, has been recently marketed and is a welcomed alternative to the standard formulation as it offers greater convenience and
Supported by a University of Malaya research grant (UMRG) RG506-13HTM. *Address correspondence to Dr Wan Ahmad Hafiz Wan Md Adnan, Division of Nephrology, Department of Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia. E-mail: wahafi[email protected] 0041-1345/16 http://dx.doi.org/10.1016/j.transproceed.2016.01.001
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flexibility to patients. This initial optimism was favored by clinical studies that have demonstrated its safety and efficacy [5] and comparable systemic drug exposure to the twice-daily Prograf [6]. In addition, it was suggested that Advograf may have better patient and graft survivals and reduction in biopsy-proven acute rejection in comparison with Prograf in a small observational study [7]. Advograf is also likely to improve medication adherence in renal transplantation patients, especially in geriatric patients [8] with comorbidities and polypharmacy [9]. Although this newer formulation has been available in Western countries since 2007, Advograf has just made its way to South East Asian countries recently and patients have started to be switched to this formulation slowly. Although bioequivalence was demonstrated between Advograf and Prograf, several reports have shown a significant decrease in tacrolimus exposure upon conversion to Advograf [10e12]. Crespo et al [13] reported that a 50% higher dose of Advograf during the first 6 months was required to achieve trough level (C0) equivalent to Prograf in renal transplant recipients. Other studies have demonstrated a 10% lower systemic steady state exposure with Advograf, regardless of gender, race, or presence of diabetes [14]. Reports of these differences in pharmacokinetic profiles upon conversion are mostly derived from stable European and American populations, whereas there is a dearth of studies looking at this problem in the Asian population [15]. Variations in the individuals’ pharmacokinetics profiles may be partly explained by the variable expression of functional alleles or polymorphisms for cytochrome P450 3A5 gene (CYP3A5) [16]. Among the several variants of alleles in the CYP3A5 gene, the ‘wild-type’ allele (CYP3A5*1) and the nonfunctional allele (CYP3A5*3) are the most relevant [17]. These subtle genetic polymorphisms may influence the dose requirement widely from person to person. The CYP3A5*3 allele leads to aberrant CYP3A5 messenger RNA splicing that causes alterations and differing levels of CYP3A5 expression [16]. This pattern in turn alters CYP3A5 activities, resulting in a seismic shift in medication dosage requirement. Thus, CYP3A5*1 carriers with a functional CYP3A5 require a higher dose of tacrolimus, and, by contrast a nonfunctional allele CYP3A5*3 demonstrates the opposite effect. CYP3A5 polymorphisms are more common in populations whose genetic origin is closer to the earth equator [18], with nearly half of the South Asians being CYP3A5 expressers (CYP3A5*1) [19]. Our study is the first to examine the variability of trough levels and daily dose of tacrolimus when renal transplant recipients were switched from Prograf to Advograf in the Malaysian population. With the switch from Prograf to Advograf in our population once it become available, it is of interest to examine the changes in the variability of C0 and dosing following conversion in our multiethnic population, which is quite representative of the South East Asian population. It is also important to examine if the differences in C0 and dosage requirement between these 2 formulations are partly explained by different variants of the CYP3A5.
MAC GUAD, ZAHARAN, CHIK ET AL
METHODS Patient Selection All procedures performed in studies involving human participants were in accordance with the ethical standards of the University of Malaya Medical Centre (UMMC) ethics committee (reference number 989.7) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. For the purpose of the study, posterenal transplantation patients who had undergone milligram-for-milligram switch from twice-daily (Prograf) to once-daily (Advograf) tacrolimus formulations were recruited from the UMMC, Kuala Lumpur, Malaysia. This center is one of the main tertiary referral centers for care of posterenal transplantation patients in Malaysia. Written informed consent was obtained from all participants prior to the study. Inclusion criteria included stable Prograf dosage and having been switched to Advograf for at least 6 months, no rejection episodes within the last 1 year, no transplantation with other organs, and not receiving other nonimmunosuppressive drugs that may interact with the pharmacokinetics of tacrolimus. Triple immunosuppression regimen used in this center was a combination of prednisolone, tacrolimus, and azathioprine or mycophenolate mofetil/acid.
Pharmacokinetic Parameters of Tacrolimus Five readings of steady-state C0 of Prograf, as determined using therapeutic drug monitoring (TDM), were obtained within the last 6 months prior to conversion to Advograf. For Advograf, C0 were obtained starting from the first month of the conversion (first, second, third, fourth, and sixth month). The corresponding dosage of both formulations of tacrolimus for each C0 was obtained from their medical records. According to the UMMC protocol on renal transplantation, tacrolimus dosing will be adjusted to attain the target tacrolimus C0 as follows: 12e15 ng/mL during the first 3 months after kidney transplantation, 8e12 ng/mL from months 4 months to 1 year, and 3e8 ng/mL thereafter. Nevertheless, the daily tacrolimus dose was adjusted according to clinical judgement of the attending clinicians, especially in cases of suspected toxicity or underdosing. In addition, biochemical parameters, including creatinine, albumin (Alb), aspartate transferase (AST), alanine transferase (ALT), and hematocrit (Hct), which may affect the trough levels of tacrolimus [20], were obtained concurrently.
Genotyping Approximately 4 mL of venous blood was withdrawn from each patient and DNA was extracted using a QIAamp Blood kit (Qiagen, Hilden, Germany) according to the manufacturer’s protocol. Genotyping for CYP3A5 polymorphisms was performed using Taqman genotyping assays (Applied Biosystems, Foster City, United States) on an ABI PRISM 7500 Step-One Plus Real-Time Polymerase Chain Reaction machine according to a standardized protocol. Genotyping assays were replicated in separate experiments.
Statistical Analysis Dose-adjusted trough level was calculated by dividing the trough level (ng/mL) with the dose given per kilogram of weight of the patient (mg/[kg.day]). Continuous data are presented as mean standard deviation. Patients’ genotypes were considered as categorical variables. Carriers for variant CYP3A5*1/*1, CYP3A5*1/*3, and CYP3A5*3/*3 genotypes were categorized into “highexpressor,” “intermediate-expressor,” and “low-expressor” groups, respectively. Trough levels, dose-adjusted trough levels, and dosage
CYP3A5 GENETIC POLYMORPHISM were compared between the 2 formulations of the tacrolimus using Wilcoxon signed rank test. The comparisons of the above parameters with the different CYP3A5 groups were performed using the Mann-Whitney U test. One-way analysis of variance (ANOVA) or Kruskal-Wallis test were used for multiple comparison analyses between groups. Statistical analyses were performed using SPSS version 22 (SPSS, Inc., Chicago, Ill, United States), and P < .05 is considered to be statistically significant.
RESULTS Patients Demographic
This study included 28 stable, posterenal transplantation patients (79% male; 79% of Chinese ethnicity; mean age, 35.7 10.9 years) in which renal transplantation took place between 1985 and 2014 (mean duration of conversion posttransplantation, 7.4 5.62 years). The baseline demographics and clinical characteristics of these patients are presented in Table 1. Of those, more than half had the lowexpressive genotype (CYP3A5*3/*3), a third had intermediate-expressive genotype (CYP3A5*1/*3), whereas only a minority had the high-expressive genotype (CYP3A5*1/*1) of CYP3A5 (Table 1). Renal functions as measured by creatinine levels were similar comparing between treatment with Prograf 6 months preconversion and within 6 months postconversion to Advograf as shown in Table 2. There were no significant differences between the 2 groups in terms of other biochemical parameters, such as Alb, ALT, AST, and Hct (Table 2). There were no episodes of rejection or clinical infection recorded during this study period. Comparison of Pharmacokinetic Parameters Between Two Different Tacrolimus Formulations (Prograf vs Advograf)
The whole blood tacrolimus C0 as obtained from TDM for Advograf and Prograf was maintained within the predefined target ranges before and after conversion (target range, 3e8 ng/mL). Overall, there was a significant difference in the whole-blood tacrolimus C0 between the 2 groups (6.16 1.74 ng/mL vs 4.90 1.06 ng/mL, P ¼ .0001). The overall mean dose of tacrolimus during this 1-year study period was 3.6 1.8 mg/d. The mean daily maintenance dose of Prograf was 3.9 2.0 mg, corresponding to 0.06 mg/kg/d (range, 0.06e0.07 mg/kg/d) within the last 6 months of Prograf. This was significantly reduced to 3.3 1.7 mg/d (0.04 mg/kg/d) after 6 months conversion to Advograf (P ¼ .01; Table 2). Although the conversion was made on the range of 1.0 to 1.2 mg daily doses in 96% of the patients, 89% experienced a decrease in C0, whereas 46% experienced a decrease in the tacrolimus C0 of >20% (Table 3). Interestingly, only 14% required escalation of their daily dose to maintain target C0. CYP3A5 Polymorphism and Pharmacokinetic Parameters Between Two Different Tacrolimus Formulations
Overall, there were no significant differences in the mean C0 between the different variants of CYP3A5 as presented in Table 3. Those high-expresser (CYP3A5*1/*1) variants
83 Table 1. Baseline Demographic and Clinical Characteristics of Renal Transplant Recipients Who Were Converted From Prograf to Advograf Characteristics
Gender Males Type of transplant Cadaveric Living Race Chinese Indian Malay Body mass index (kg/m2) Age group at study (y) Age group at transplantation (y) Transplant duration (mo) Duration of dialysis prior to transplantation (mo) Primary kidney disease Hypertensive nephropathy Glomerulopathy Immunoglobulin A nephropathy Bilateral small kidneys Diabetic nephropathy Polycystic kidney disease Others Immunosuppresant drugs Steroid, tacrolimus, azathioprine Steroid, tacrolimus, mycophenolic acid Steroid, tacrolimus, mycophenolic acid Steroid, tacrolimus, mycophenolic mofetil Steroid, tacrolimus, mycophenolic mofetil Allele frequencies of CYP3A5 genotypes CYP3A5*1/*1 CYP3A5*1/*3 CYP3A5*3/*3
Frequency (%) or Means SD
22 (79%) 11 (39%) 17 (61%) 22 (79%) 2 (7%) 4 (14%) 24.9 6.0 43.1 13.0 35.7 10.9 7.4 5.6 31.5 46.1
6 5 4 4 2 1 6
(21%) (18%) (14%) (14%) (7%) (4%) (21%)
3 15 5 2 3
(11%) (54%) (18%) (7%) (11%)
4 (14%) 9 (32%) 15 (54%)
Note: CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediateexpressive genotype; CYP3A5*3/*3, low-expressive genotype.
showed a decrease in C0, whereas a total of 79% showed a decreased C0 in the low-expressive genotype. All patients with intermediate-expressive genotype showed a decreased C0 (Table 4). However, the mean maintenance dose of tacrolimus required for those with CYP3A5*1/*1 (highexpressive) was significantly higher than those with CYP3A5*1/*3 (intermediate-expressive) and CYP3A5*3/*3 (low-expressive) (P < .01) for both Advograf and Prograf (Table 4). Comparing those with CYP3A5*1/*1, the average dose-adjusted C0 of tacrolimus was significantly higher in patients with CYP3A5*3/*3 when switched to Advograf (P < .05). The trends of C0, dose, and dose-adjusted C0 for both Prograf and Advograf for the different CYP3A5 variants within each 6-month study period are presented in Figs 1e3, respectively. Patients with CYP3A5*1/*1 genotype required significantly larger daily doses of tacrolimus of approximately 1.3-fold higher than the CYP3A5*1/*3 genotype and 2-fold higher than CYP3A5*3/*3 in both periods of formulations. The C0 of tacrolimus did not show
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Table 2. Comparison of Mean Biochemical Parameters and Pharmacokinetics Parameters of Renal Transplant Recipients Before and After Switch From Prograf to Advograf Treatment Prograf Mean SD
Parameters
Creatinine (mg/dL) Alb (mg/dL) ALT (IU/L) AST (IU/L) Hct (%) Mean trough level of tacrolimus (ng/mL) Mean daily maintenance dose of tacrolimus (mg/d) Mean daily dose-adjusted trough level (ng.kg.day/ mg.mL) Mean daily relative tacrolimus dose (mg/[kg/d])
135.89 40.10 28.78 20.16 0.39 6.16
59.32 3.29 12.75 6.01 0.06 1.74
3.91 2.02
Advograf Mean SD
133.81 40.45 33.06 20.88 0.40 4.90
56.32 4.43 21.51 7.89 0.04 1.06
P
NS NS NS NS NS .0001
3.26 1.72 .014
135.65 88.52 123.32 56.82 NS
0.06 0.04
0.05 0.03 .03
Abbreviation: NS, not significant.
a significant difference with respect to the different variants of CYP3A5 in both formulations, which were monitored at every clinic visit. DISCUSSION
Our study is the first to examine the variability of trough levels and daily dose of tacrolimus when patients were switched from Prograf to Advograf in Malaysian renal transplant recipients. The results from the present study demonstrated that there was a significant decrease in mean C0 and daily dose of tacrolimus when patients were switched from Prograf to Advograf. The requirement for daily tacrolimus maintenance dose was significantly higher in those with CYP3A5*1/*1 than CYP3A5*1/*3 and CYP3A5*3/*3 variants in the maintenance phase for both formulations. It is also interesting to note that those with CYP3A5*3/*3 demonstrated significantly higher doseadjusted C0 with the Advograf formulation. Our study found that a significantly lower C0 was observed when patients were switched to Advograf. This is similar to findings from other studies on different populations, such as the Dutch, Spanish, and Chinese populations [15,21e23]. In contrast, a cross-over pharmacokinetic study of the 2 formulations performed in the United States showed an increase in C0 with Advograf [14], whereas other comparative pharmacokinetic studies performed in other major European countries and Australia demonstrated that the measurements of C0 were similar for both formulations over a 6- to 8-week study period [6,9]. Most of these studies were designed as industry-sponsored initiative, crossover replication pharmacokinetic studies. Ours was a pharmacokinetic study in which patients were switched from Prograf to Advograf, which was based on real clinical practice. It may also be possible that the lower C0 observed in our study was intentional to maintain the target C0 levels given that there was also a concurrent reduction of
Table 3. Summary of Association Between Different CYP3A5 Variants With Ratio of Conversion and Changes in Dose and Trough Level of Tacrolimus Formulations Patient
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Variants
CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*1/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3
Ratio of Dose of Reduction/ Trough of Reduction/ Conversion Increment (%) Increment (%)
1:1 1:0.6 1:1 1:1 1:1.8 1.7:1 1.4:1 1.2:1 1:1 1:1 1.5:1 1:1 1.1:1 3.5:1 1:1.3 1.3:1 1.2:1 1:1.6 1:1.1 1:1 1.2:1 1:1 1:1 1:1 2:1 1:1 1.3:1 1.2:1
0 (No change) Y44 0 (No change) 0 (No change) [44 Y40 Y26 Y17 0 (No change) 0 (No change) Y33 0 (No change) Y12 Y71 [33 Y20 Y17 [60 [7 0 (No change) Y17 0 (No change) 0 (No change) 0 (No change) Y50 0 (No change) Y20 Y14
Y31 [16 Y12 Y18 Y9 Y17 Y25 Y26 Y15 Y14 Y3 Y45 Y22 [37 Y17 Y2 Y54 Y22 Y24 Y20 Y28 Y18 Y17 Y32 0 (No change) Y29 Y39 Y31
the maintenance dose. The C0 of tacrolimus in our study was in the lower range of the recommended target, probably because the study population consisted mainly of low-risk patients (panel-reactive antibodies [PRA] <10% at transplantation, no acute rejection episodes in >12 months, and no previous graft loss for immunologic reasons prior to participation in the study). Nevertheless, the no biopsyproven acute rejection rate suggested that the lower C0 of tacrolimus as a surrogate of exposure was sufficient to avoid rejection episodes. Lower doses of tacrolimus were required when patients were switched to Advograf in our population. This is in contrast to a 12-week clinical study in a stable Chinese population that reported a significant escalation of dose after 8 weeks of conversion to Advograf to achieve similar C0 [24]. Another study in a Spanish population also showed an increase in dose in Advograf formulations [13]. Our study followed patients for 6 months postconversion, which provided a reasonable period of observation that could possibly explain the differing result. The conversion ratios used in the present study ranged between 1:0.6 mg and 1:3.5 mg, which were wider compared with the study in the Chinese population (1:1 mg) [24]. Another important contributory factor may be drug interactions, with corticosteroid
CYP3A5 GENETIC POLYMORPHISM
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Table 4. Summary of Whole-Blood Tacrolimus Pharmacokinetic Parameters of Renal Transplant Recipients Before and After Switch From Prograf to Advograf Treatment in Different Variants of CYP3A5 Whole-Blood Tacrolimus Pharmacokinetic Parameters Characteristics
Prograf Mean SD
Advograf Mean SD
Tacrolimus trough level (ng/mL) CYP3A5*1/*1 6.32 0.83 5.57 0.40 CYP3A5*1/*3 6.41 1.61 5.07 1.02 CYP3A5*3/*3 5.96 2.03 4.61 1.14 P (high- vs intermediateNS NS vs low-expressive) Tacrolimus dose (mg/d) CYP3A5*1/*1 6.20 2.97 5.10 1.52 CYP3A5*1/*3 4.39 1.69 4.27 1.74 CYP3A5*3/*3 3.01 1.35 2.17 0.76 P (high- vs intermediate.008 <.001 vs low-expressive) Relative tacrolimus dose (mg/[kg/d]) CYP3A5*1/*1 0.11 0.06 0.08 0.02 CYP3A5*1/*3 0.07 0.03 0.07 0.03 CYP3A5*3/*3 0.04 0.02 0.03 0.01 P (high- vs intermediate.003 <.001 vs low-expressive) Dose-adjusted trough level of tacrolimus (ng.kg.day/mg.mL) CYP3A5*1/*1 74.89 42.79 77.81 27.55 CYP3A5*1/*3 106.23 57.73 87.52 47.72 CYP3A5*3/*3 169.50 99.89 156.94 50.81 P (high- vs intermediateNS .002 vs low-expressive)
Fig 2. Comparison of whole-blood dose-adjusted level of renal transplant recipients before and after switch from Prograf to Advograf treatment in different variants of CYP3A5 Note: Data were presented as mean SD. CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediate-expressive genotype; CYP3A5*3/*3, low-expressive genotype.
having an influence on pharmacokinetics of tacrolimus even at a low dose [25]. Wu et al (2013) reported that corticosteroid was discontinued 1 year after transplantation in the Chinese study [15]. In our study population, corticosteroid was part of the triple regimen throughout the study period.
In addition, the calculation of dose requirement differs according to body weight (mg/kg/d). However, the body mass indexes in our population and the Chinese populations were quite similar (24.9 6.0 vs 24.6 3.0). In addition, 19% of retransplantation patients were included in the Spanish study. The prevalence of expressive-genotype in our population reveals a reliable genotypeephenotype association across a wide range of ethnic and geographically different populations: CYP3A5*1/*1 (4%), CYP3A5*1/*3 (9%), and CYP3A5*3/*3 (15%) [19]. This distribution is consistent with another study on renal transplant recipients conducted in Taiwan [26]. For both formulations, this study demonstrated that patients with CYP3A5*3/*3 required significantly lower daily maintenance doses as demonstrated by higher tacrolimus daily dose requirements and lower relative tacrolimus dose to reach desired C0 when compared
Fig 1. Comparison of whole-blood trough level of renal transplant recipients before and after switch from Prograf to Advograf treatment in different variants of CYP3A5. Note: Data were presented as mean SD. CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediate-expressive genotype; CYP3A5*3/*3, low-expressive genotype.
Fig 3. Comparison of whole-blood daily maintenance dose (mean SD) of renal transplant recipients before and after switch from Prograf to Advograf treatment in different variants of CYP3A5 Note: CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediate-expressive genotype; CYP3A5*3/*3, low-expressive genotype.
Note: CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediateexpressive genotype; CYP3A5*3/*3, low-expressive genotype.
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with those with CYP3A5*1/*1 or CYP3A5*1/*3. This is consistent with other studies across a range of adult populations in Germany and France following conversion or comparable pharmacokinetic study [27,28]. Increased activity in hepatic CYP3A5 microsomal enzymes caused by the presence of a CYP3A5*1 allele leads to rapid drug clearance and hence higher dose requirements are needed [29]. Interestingly, compared with the patients with CYP3A5*1/*1 genotype, the average dose-adjusted C0 of tacrolimus was significantly higher in patients with CYP3A5*1/*3 or CYP3A5*3/*3 genotypes for both formulations. This is consistent with the findings by Hamzah et al that have shown that CYP3A5 polymorphisms significantly impact tacrolimus C0 in the Malaysian renal transplantation population [30]. However, the study by Hamzah et al was focused on the twice-daily tacrolimus formulation, Prograf. Advograf is a prolonged-release tacrolimus formulation that is released slowly but distributed further in the tissues of stomach, jejunum, and ileum [10]. A wide interindividual expression of CYP3A5 messenger RNA, which influences the protein translation in each of these tissues in the gastrointestinal tract [31], would have significant impact on the differences of its pharmacokinetics compared with Prograf formulations. Interestingly, compared with our study, the mean tacrolimus C0 was no longer significant among variants after 3 months posttransplantation but, similarly, the overall dose-adjusted levels were nearly 2-fold higher in CYP3A5*3/*3 genotypes than in CYP3A5*1/*1 genotypes in the Korean population [32]. This study has several strengths. This study added valuable insight into the influence of CYP3A5 polymorphism on the pharmacokinetics of tacrolimus of different formulations in the South East Asian population. This population differs genetically from the white and African population in which most other studies are based. Clinical factors, such as time from transplantation, patient age and race, food administration, Alb and Hct values, liver function, gastrointestinal motility, and concomitant medication, which could affect the pharmacokinetics of tacrolimus [10], were monitored as best that we could. The use of validated assay methods in determining tacrolimus concentrations ensures accurate measures of systemic exposure. In addition, the 6month preconversion and postconversion period of observation is adequate to show the differences in tacrolimus formulation pharmacokinetics. The relatively small patient population of this study may have limited our ability to detect a biologically meaningful difference. This is due to the fact that Advograf has only recently become available in Malaysia, and patients have been slowly switched to this formulation. However, our center has the highest number of patients on this new formulation compared with other centers caring for renal transplantation patients in Malaysia. It is of interest to note that despite the small number of patients, we were able to demonstrate significant differences in the pharmacokinetic profiles as well as the association between CYP3A5 and
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dose requirements. Our patients were switched to Advograf without washout periods. The lack of washout periods between formulations may have resulted in carryover effects. Furthermore, patients or their caretakers were advised to take the medication before their meal but we cannot exclude if some did not adhere to this instruction, which could affect the overall drug exposure [12]. Due to the nature of our population, which consists of several ethnicities, a small number of patients were pooled together and the effect of CYP3A5 in each ethnicity could not be examined. In addition, there is a variation in the duration of transplant before switching of tacrolimus formulations. This may induce great variability in the C0 because the dose adjustment depends over time on the clinician evaluations and TDM result. This study only focused on CYP3A5, whereas other polymorphisms such as hepatic cytochrome CYP3A4 gene and drug transporter MDR1 gene were not investigated. In summary, this is the first study conducted in a heterogenous group of stable Malaysian renal transplant recipients that showed that the requirement for daily maintenance dose of tacrolimus differed between CYP3A5 variants in which daily maintenance dose was higher in those with CYP3A5*1/*1 variants. In addition, those carrying CYP3A5*3/*3 demonstrated significantly higher doseadjusted C0 with Advograf. As our hospitals are in the phases of converting renal transplant recipients to the more convenient Advograf formulations, the identification of CYP3A5 polymorphism would be a useful way to optimize personalized immunosuppressive therapy of tacrolimus before conversion to minimize the risk for undertherapeutic or overtherapeutic regimens and to avoid incidence of chronic rejection associated with long-term outcome of renal allografts in our renal transplant recipients. ACKNOWLEDGMENTS We gratefully acknowledge the patients for their participation in this study, as well as the staff nurses and transplantation team of the hospital for their assistance in recruiting the patients.
REFERENCES [1] Zuo XC, Ng CM, Barrett JS, Luo AJ, Zhang BK, Deng CH, et al. Effects of CYP3A4 and CYP3A5 polymorphisms on tacrolimus pharmacokinetics in Chinese adult renal transplant recipients: a population pharmacokinetic analysis. Pharmacogenet Genomics 2013;23(5):251e61. [2] Barraclough KA, Isbel NM, Johnson DW, Hawley CM, Lee KJ, Mcwhinney BC, et al. A limited sampling strategy for the simultaneous estimation of tacrolimus, mycophenolic acid and unbound prednisolone exposure in adult kidney transplant recipients. Nephrology 2012;17(3):294e9. [3] Tada H, Tsuchiya N, Satoh S, Kagaya H, Li Z, Sato K, et al. Impact of CYP3A5 and MDR1(ABCB1) C3435T polymorphisms on the pharmacokinetics of tacrolimus in renal transplant recipients. Transplant Proc 2005;37(4):1730e2. [4] Ichimaru N, Kakuta Y, Abe T, Okumi M, Imamura R, Isaka Y, et al. Treatment adherence in renal transplant recipients: a questionnaire survey on immunosuppressants. Transplant Proc 2008.
CYP3A5 GENETIC POLYMORPHISM [5] Shah DS, Shrestha S, Kafle MP. Renal transplantation in Nepal: beginning of a new era! Nephrology 2013;18(5):369e75. [6] Wlodarczyk Z, Squifflet JP, Ostrowski M, Rigotti P, Stefoni S, Citterio F, et al. Pharmacokinetics for once- versus twicedaily tacrolimus formulations in de novo kidney transplantation: a randomized, open-label trial. Am J Transplant 2009;9(11):2505e13. [7] Alloway R, Steinberg S, Khalil K, Gourishankar S, Miller J, Norman D, et al. Two years postconversion from a prograf-based regimen to a once-daily tacrolimus extended-release formulation in stable kidney transplant recipients. Transplantation 2007;83(12): 1648e51. [8] Kramer A, Stel V, Zoccali C, Heaf J, Ansell D, GronhagenRiska C, et al. An update on renal replacement therapy in Europe: ERA-EDTA Registry data from 1997 to 2006. Nephrol Dial Transplant 2009;24(12):3557e66. [9] van Hooff J, Van der Walt I, Kallmeyer J, Miller D, Dawood S, Moosa MR, et al. Pharmacokinetics in stable kidney transplant recipients after conversion from twice-daily to once-daily tacrolimus formulations. Ther Drug Monit 2012;34(1):46e52. [10] Barraclough KA, Isbel NM, Johnson DW, Campbell SB, Staatz CE. Once-versus twice-daily tacrolimus. Drugs 2011;71(12): 1561e77. [11] Hougardy J-M, de Jonge H, Kuypers D, Abramowicz D. The once-daily formulation of tacrolimus: a step forward in kidney transplantation? Transplantation 2012;93(3):241e3. [12] Staatz CE, Tett SE. Clinical pharmacokinetics of once-daily tacrolimus in solid-organ transplant patients. Clin Pharmacokinet 2015. [13] Crespo M, Mir M, Marin M, Hurtado S, Estadella C, Guri X, et al. De novo kidney transplant recipients need higher doses of Advagraf compared with Prograf to get therapeutic levels. Transplant Proc 2009. [14] Alloway R, Steinberg S, Khalil K, Gourishankar S, Miller J, Norman D, et al. Conversion of stable kidney transplant recipients from a twice daily Prograf-based regimen to a once daily modified release tacrolimus-based regimen. Transplant Proc 2005. [15] Wu S-W, Tsai H-C, Tsai P-Y, Hung T-W, Chang H-R, Lian J-D. Conversion to prolonged release tacrolimus formulation in stable kidney transplant recipients. Age (years) 2013;54:10.4. [16] Anglicheau D, Legendre C, Beaune P, Thervet E. Cytochrome P450 3A polymorphisms and immunosuppressive drugs: an update. 2007. [17] Jacobson PA, Oetting WS, Brearley AM, Leduc R, Guan W, Schladt D, et al. Novel polymorphisms associated with tacrolimus trough concentrations: results from a multicenter kidney transplant consortium. Transplantation 2011;91(3):300e8. [18] Thompson EE, Kuttab-Boulos H, Witonsky D, Yang L, Roe BA, Di Rienzo A. CYP3A variation and the evolution of saltsensitivity variants. Am J Hum Genet 2004;75(6):1059e69. [19] MacPhee IA, Holt DW. A pharmacogenetic strategy for immunosuppression based on the CYP3A5 genotype. Transplantation 2008;85(2):163e5. [20] Niioka T, Satoh S, Kagaya H, Numakura K, Inoue T, Saito M, et al. Comparison of pharmacokinetics and
87 pharmacogenetics of once- and twice-daily tacrolimus in the early stage after renal transplantation. Transplantation 2012;94(10): 1013e9. [21] Roodnat M, Kho MM, Weimar W, Dennis A, Hesselink M. Conversion from twice-daily to once-daily tacrolimus does not reduce intra-patient variability in tacrolimus exposure. 2014. [22] Hougardy JM, Broeders N, Kianda M, Massart A, Madhoun P, Le Moine A, et al. Conversion from Prograf to Advagraf among kidney transplant recipients results in sustained decrease in tacrolimus exposure. Transplantation 2011;91(5):566e9. [23] Guirado L, Cantarell C, Franco A, Huertas E, Fructuoso A, Fernández A, et al. Efficacy and safety of conversion from twicedaily to once-daily tacrolimus in a large cohort of stable kidney transplant recipients. Am J Transplant 2011;11(9):1965e71. [24] Ma MK, Kwan LP, Mok MM, Yap DY, Tang CS, Chan TM. Significant reduction of Tacrolimus trough level after conversion from twice daily Prograf to once daily Advagraf in Chinese renal transplant recipients with or without concomitant diltiazem treatment. Ren Fail 2013;35(7):942e5. [25] Press RR, Ploeger BA, den Hartigh J, van der Straaten T, van Pelt J, Danhof M, et al. Explaining variability in tacrolimus pharmacokinetics to optimize early exposure in adult kidney transplant recipients. Ther Drug Monit 2009;31(2):187e97. [26] Wu M-J, Chang C-H, Cheng C-Y, Shu K-H, Chen C-H, Cheng C-H, et al. Reduced variability of tacrolimus trough level in once-daily tacrolimus-based Taiwanese kidney transplant recipients with high-expressive genotype of cytochrome P450 3A5. Transplant Proc 2014. [27] Wehland M, Bauer S, Brakemeier S, Burgwinkel P, Glander P, Kreutz R, et al. Differential impact of the CYP3A5* 1 and CYP3A5* 3 alleles on pre-dose concentrations of two tacrolimus formulations. Pharmacogenet Genomics 2011;21(4): 179e84. [28] Glowacki F, Lionet A, Hammelin J-P, Labalette M, Provôt F, Hazzan M, et al. Influence of cytochrome P450 3A5 (CYP3A5) genetic polymorphism on the pharmacokinetics of the prolonged-release, once-daily formulation of tacrolimus in stable renal transplant recipients. Clin Pharmacokinet 2011;50(7):451e9. [29] Dai Y, Hebert MF, Isoherranen N, Davis CL, Marsh C, Shen DD, et al. Effect of CYP3A5 polymorphism on tacrolimus metabolic clearance in vitro. Drug Metab Dispos 2006;34(5): 836e47. [30] Hamzah S, Teh LK, Siew JSK, Ahmad G, Wong HS, Zakaria ZA, et al. Pharmacogenotyping of CYP3A5 in predicting dose-adjusted trough levels of tacrolimus among Malaysian kidneytransplant patients. Can J Physiol Pharmacol 2013;92(1):50e7. [31] Canaparo R, Finnström N, Serpe L, Nordmark A, Muntoni E, Eandi M, et al. Expression of CYP3A isoforms and pglycoprotein in human stomach, jejunum and ileum. Clin Exp Pharmacol Physiol 2007;34(11):1138e44. [32] Kim I-W, Moon YJ, Ji E, Im Kim K, Han N, Kim SJ, et al. Clinical and genetic factors affecting tacrolimus trough levels and drug-related outcomes in Korean kidney transplant recipients. Eur J Clin Pharmacol 2012;68(5):657e69.
ABSTRACT Background. The aim of this study was to compare the within-patient variability trough levels (Co), dose-adjusted Co, and dose requirements of Prograf and Advograf with CYP3A5 polymorphisms in Malaysia renal transplant recipients. Methods. Stable posterenal transplantation patients switched from Prograf to Advograf were retrospectively identified from University Malaya Medical Centre (n ¼ 28). Co and concomitant tacrolimus dose 6 months preconversion and postconversion were examined. CYP3A5 was genotyped using reverse transcriptase polymerase chain reaction. Wilcoxon signed rank test and Mann-Whitney U test were used to compare Co and dose between formulations and according to genotypes. Results. There was a significant difference in the whole-blood tacrolimus Co between the 2 groups (6.16 1.74 ng/mL vs 4.90 1.06 ng/mL; P ¼ .0001). The mean daily maintenance dose of Prograf was 3.9 2.0 mg/kg (0.06 mg/kg/d), which was reduced to 3.3 1.7 mg/d (0.04 mg/kg/d) with Advograf (P ¼ .01). The mean maintenance dose of tacrolimus required for those with CYP3A5*1/*1 (high-expressive) was significantly higher than those with CYP3A5*1/*3 (intermediate-expressive) and CYP3A5*3/*3 (lowexpressive) (P < .01) for both formulations. Comparing those with CYP3A5*1/*1, the average dose-adjusted Co was significantly higher in patients with CYP3A5*3/*3 with Advograf (P < .05). Conclusions. The requirement for daily maintenance dose was higher in those with CYP3A5*1/*1 variants in both tacrolimus formulations in the Malaysian patients. Furthermore, those with CYP3A5*3/*3 demonstrated significantly higher dose-adjusted Co with Advograf.
S
INCE the approval of tacrolimus by the U.S. Food and Drug Administration (FDA) in April 1994 for allogenic liver transplant recipients, it has emerged as an alternative to cyclosporine in renal transplantation for the prevention of allograft rejection. In fact, currently more than two thirds of all renal transplant recipients are prescribed tacrolimus as part of their immunosuppressant regimen [1]. One of the drawbacks of tacrolimus is its wide within-patient and interpatient variabilities [2], which lead to this drug having a narrow therapeutic index [3]. In addition, for more than 10 years, oral tacrolimus has only been available as a standard twice-daily formulation manufactured by Astellas Pharma Europe Ltd (Staines, United Kingdom) as Prograf. As in the case of any drugs that have ª 2016 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
Transplantation Proceedings, 48, 81e87 (2016)
to be consumed multiple times daily, adherence to medication is a recognized challenge [4]. A newer, prolonged-release formulation of tacrolimus (Advograf), which only needs to be taken once-daily, has been recently marketed and is a welcomed alternative to the standard formulation as it offers greater convenience and
Supported by a University of Malaya research grant (UMRG) RG506-13HTM. *Address correspondence to Dr Wan Ahmad Hafiz Wan Md Adnan, Division of Nephrology, Department of Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia. E-mail: wahafi[email protected] 0041-1345/16 http://dx.doi.org/10.1016/j.transproceed.2016.01.001
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flexibility to patients. This initial optimism was favored by clinical studies that have demonstrated its safety and efficacy [5] and comparable systemic drug exposure to the twice-daily Prograf [6]. In addition, it was suggested that Advograf may have better patient and graft survivals and reduction in biopsy-proven acute rejection in comparison with Prograf in a small observational study [7]. Advograf is also likely to improve medication adherence in renal transplantation patients, especially in geriatric patients [8] with comorbidities and polypharmacy [9]. Although this newer formulation has been available in Western countries since 2007, Advograf has just made its way to South East Asian countries recently and patients have started to be switched to this formulation slowly. Although bioequivalence was demonstrated between Advograf and Prograf, several reports have shown a significant decrease in tacrolimus exposure upon conversion to Advograf [10e12]. Crespo et al [13] reported that a 50% higher dose of Advograf during the first 6 months was required to achieve trough level (C0) equivalent to Prograf in renal transplant recipients. Other studies have demonstrated a 10% lower systemic steady state exposure with Advograf, regardless of gender, race, or presence of diabetes [14]. Reports of these differences in pharmacokinetic profiles upon conversion are mostly derived from stable European and American populations, whereas there is a dearth of studies looking at this problem in the Asian population [15]. Variations in the individuals’ pharmacokinetics profiles may be partly explained by the variable expression of functional alleles or polymorphisms for cytochrome P450 3A5 gene (CYP3A5) [16]. Among the several variants of alleles in the CYP3A5 gene, the ‘wild-type’ allele (CYP3A5*1) and the nonfunctional allele (CYP3A5*3) are the most relevant [17]. These subtle genetic polymorphisms may influence the dose requirement widely from person to person. The CYP3A5*3 allele leads to aberrant CYP3A5 messenger RNA splicing that causes alterations and differing levels of CYP3A5 expression [16]. This pattern in turn alters CYP3A5 activities, resulting in a seismic shift in medication dosage requirement. Thus, CYP3A5*1 carriers with a functional CYP3A5 require a higher dose of tacrolimus, and, by contrast a nonfunctional allele CYP3A5*3 demonstrates the opposite effect. CYP3A5 polymorphisms are more common in populations whose genetic origin is closer to the earth equator [18], with nearly half of the South Asians being CYP3A5 expressers (CYP3A5*1) [19]. Our study is the first to examine the variability of trough levels and daily dose of tacrolimus when renal transplant recipients were switched from Prograf to Advograf in the Malaysian population. With the switch from Prograf to Advograf in our population once it become available, it is of interest to examine the changes in the variability of C0 and dosing following conversion in our multiethnic population, which is quite representative of the South East Asian population. It is also important to examine if the differences in C0 and dosage requirement between these 2 formulations are partly explained by different variants of the CYP3A5.
MAC GUAD, ZAHARAN, CHIK ET AL
METHODS Patient Selection All procedures performed in studies involving human participants were in accordance with the ethical standards of the University of Malaya Medical Centre (UMMC) ethics committee (reference number 989.7) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. For the purpose of the study, posterenal transplantation patients who had undergone milligram-for-milligram switch from twice-daily (Prograf) to once-daily (Advograf) tacrolimus formulations were recruited from the UMMC, Kuala Lumpur, Malaysia. This center is one of the main tertiary referral centers for care of posterenal transplantation patients in Malaysia. Written informed consent was obtained from all participants prior to the study. Inclusion criteria included stable Prograf dosage and having been switched to Advograf for at least 6 months, no rejection episodes within the last 1 year, no transplantation with other organs, and not receiving other nonimmunosuppressive drugs that may interact with the pharmacokinetics of tacrolimus. Triple immunosuppression regimen used in this center was a combination of prednisolone, tacrolimus, and azathioprine or mycophenolate mofetil/acid.
Pharmacokinetic Parameters of Tacrolimus Five readings of steady-state C0 of Prograf, as determined using therapeutic drug monitoring (TDM), were obtained within the last 6 months prior to conversion to Advograf. For Advograf, C0 were obtained starting from the first month of the conversion (first, second, third, fourth, and sixth month). The corresponding dosage of both formulations of tacrolimus for each C0 was obtained from their medical records. According to the UMMC protocol on renal transplantation, tacrolimus dosing will be adjusted to attain the target tacrolimus C0 as follows: 12e15 ng/mL during the first 3 months after kidney transplantation, 8e12 ng/mL from months 4 months to 1 year, and 3e8 ng/mL thereafter. Nevertheless, the daily tacrolimus dose was adjusted according to clinical judgement of the attending clinicians, especially in cases of suspected toxicity or underdosing. In addition, biochemical parameters, including creatinine, albumin (Alb), aspartate transferase (AST), alanine transferase (ALT), and hematocrit (Hct), which may affect the trough levels of tacrolimus [20], were obtained concurrently.
Genotyping Approximately 4 mL of venous blood was withdrawn from each patient and DNA was extracted using a QIAamp Blood kit (Qiagen, Hilden, Germany) according to the manufacturer’s protocol. Genotyping for CYP3A5 polymorphisms was performed using Taqman genotyping assays (Applied Biosystems, Foster City, United States) on an ABI PRISM 7500 Step-One Plus Real-Time Polymerase Chain Reaction machine according to a standardized protocol. Genotyping assays were replicated in separate experiments.
Statistical Analysis Dose-adjusted trough level was calculated by dividing the trough level (ng/mL) with the dose given per kilogram of weight of the patient (mg/[kg.day]). Continuous data are presented as mean standard deviation. Patients’ genotypes were considered as categorical variables. Carriers for variant CYP3A5*1/*1, CYP3A5*1/*3, and CYP3A5*3/*3 genotypes were categorized into “highexpressor,” “intermediate-expressor,” and “low-expressor” groups, respectively. Trough levels, dose-adjusted trough levels, and dosage
CYP3A5 GENETIC POLYMORPHISM were compared between the 2 formulations of the tacrolimus using Wilcoxon signed rank test. The comparisons of the above parameters with the different CYP3A5 groups were performed using the Mann-Whitney U test. One-way analysis of variance (ANOVA) or Kruskal-Wallis test were used for multiple comparison analyses between groups. Statistical analyses were performed using SPSS version 22 (SPSS, Inc., Chicago, Ill, United States), and P < .05 is considered to be statistically significant.
RESULTS Patients Demographic
This study included 28 stable, posterenal transplantation patients (79% male; 79% of Chinese ethnicity; mean age, 35.7 10.9 years) in which renal transplantation took place between 1985 and 2014 (mean duration of conversion posttransplantation, 7.4 5.62 years). The baseline demographics and clinical characteristics of these patients are presented in Table 1. Of those, more than half had the lowexpressive genotype (CYP3A5*3/*3), a third had intermediate-expressive genotype (CYP3A5*1/*3), whereas only a minority had the high-expressive genotype (CYP3A5*1/*1) of CYP3A5 (Table 1). Renal functions as measured by creatinine levels were similar comparing between treatment with Prograf 6 months preconversion and within 6 months postconversion to Advograf as shown in Table 2. There were no significant differences between the 2 groups in terms of other biochemical parameters, such as Alb, ALT, AST, and Hct (Table 2). There were no episodes of rejection or clinical infection recorded during this study period. Comparison of Pharmacokinetic Parameters Between Two Different Tacrolimus Formulations (Prograf vs Advograf)
The whole blood tacrolimus C0 as obtained from TDM for Advograf and Prograf was maintained within the predefined target ranges before and after conversion (target range, 3e8 ng/mL). Overall, there was a significant difference in the whole-blood tacrolimus C0 between the 2 groups (6.16 1.74 ng/mL vs 4.90 1.06 ng/mL, P ¼ .0001). The overall mean dose of tacrolimus during this 1-year study period was 3.6 1.8 mg/d. The mean daily maintenance dose of Prograf was 3.9 2.0 mg, corresponding to 0.06 mg/kg/d (range, 0.06e0.07 mg/kg/d) within the last 6 months of Prograf. This was significantly reduced to 3.3 1.7 mg/d (0.04 mg/kg/d) after 6 months conversion to Advograf (P ¼ .01; Table 2). Although the conversion was made on the range of 1.0 to 1.2 mg daily doses in 96% of the patients, 89% experienced a decrease in C0, whereas 46% experienced a decrease in the tacrolimus C0 of >20% (Table 3). Interestingly, only 14% required escalation of their daily dose to maintain target C0. CYP3A5 Polymorphism and Pharmacokinetic Parameters Between Two Different Tacrolimus Formulations
Overall, there were no significant differences in the mean C0 between the different variants of CYP3A5 as presented in Table 3. Those high-expresser (CYP3A5*1/*1) variants
83 Table 1. Baseline Demographic and Clinical Characteristics of Renal Transplant Recipients Who Were Converted From Prograf to Advograf Characteristics
Gender Males Type of transplant Cadaveric Living Race Chinese Indian Malay Body mass index (kg/m2) Age group at study (y) Age group at transplantation (y) Transplant duration (mo) Duration of dialysis prior to transplantation (mo) Primary kidney disease Hypertensive nephropathy Glomerulopathy Immunoglobulin A nephropathy Bilateral small kidneys Diabetic nephropathy Polycystic kidney disease Others Immunosuppresant drugs Steroid, tacrolimus, azathioprine Steroid, tacrolimus, mycophenolic acid Steroid, tacrolimus, mycophenolic acid Steroid, tacrolimus, mycophenolic mofetil Steroid, tacrolimus, mycophenolic mofetil Allele frequencies of CYP3A5 genotypes CYP3A5*1/*1 CYP3A5*1/*3 CYP3A5*3/*3
Frequency (%) or Means SD
22 (79%) 11 (39%) 17 (61%) 22 (79%) 2 (7%) 4 (14%) 24.9 6.0 43.1 13.0 35.7 10.9 7.4 5.6 31.5 46.1
6 5 4 4 2 1 6
(21%) (18%) (14%) (14%) (7%) (4%) (21%)
3 15 5 2 3
(11%) (54%) (18%) (7%) (11%)
4 (14%) 9 (32%) 15 (54%)
Note: CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediateexpressive genotype; CYP3A5*3/*3, low-expressive genotype.
showed a decrease in C0, whereas a total of 79% showed a decreased C0 in the low-expressive genotype. All patients with intermediate-expressive genotype showed a decreased C0 (Table 4). However, the mean maintenance dose of tacrolimus required for those with CYP3A5*1/*1 (highexpressive) was significantly higher than those with CYP3A5*1/*3 (intermediate-expressive) and CYP3A5*3/*3 (low-expressive) (P < .01) for both Advograf and Prograf (Table 4). Comparing those with CYP3A5*1/*1, the average dose-adjusted C0 of tacrolimus was significantly higher in patients with CYP3A5*3/*3 when switched to Advograf (P < .05). The trends of C0, dose, and dose-adjusted C0 for both Prograf and Advograf for the different CYP3A5 variants within each 6-month study period are presented in Figs 1e3, respectively. Patients with CYP3A5*1/*1 genotype required significantly larger daily doses of tacrolimus of approximately 1.3-fold higher than the CYP3A5*1/*3 genotype and 2-fold higher than CYP3A5*3/*3 in both periods of formulations. The C0 of tacrolimus did not show
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MAC GUAD, ZAHARAN, CHIK ET AL
Table 2. Comparison of Mean Biochemical Parameters and Pharmacokinetics Parameters of Renal Transplant Recipients Before and After Switch From Prograf to Advograf Treatment Prograf Mean SD
Parameters
Creatinine (mg/dL) Alb (mg/dL) ALT (IU/L) AST (IU/L) Hct (%) Mean trough level of tacrolimus (ng/mL) Mean daily maintenance dose of tacrolimus (mg/d) Mean daily dose-adjusted trough level (ng.kg.day/ mg.mL) Mean daily relative tacrolimus dose (mg/[kg/d])
135.89 40.10 28.78 20.16 0.39 6.16
59.32 3.29 12.75 6.01 0.06 1.74
3.91 2.02
Advograf Mean SD
133.81 40.45 33.06 20.88 0.40 4.90
56.32 4.43 21.51 7.89 0.04 1.06
P
NS NS NS NS NS .0001
3.26 1.72 .014
135.65 88.52 123.32 56.82 NS
0.06 0.04
0.05 0.03 .03
Abbreviation: NS, not significant.
a significant difference with respect to the different variants of CYP3A5 in both formulations, which were monitored at every clinic visit. DISCUSSION
Our study is the first to examine the variability of trough levels and daily dose of tacrolimus when patients were switched from Prograf to Advograf in Malaysian renal transplant recipients. The results from the present study demonstrated that there was a significant decrease in mean C0 and daily dose of tacrolimus when patients were switched from Prograf to Advograf. The requirement for daily tacrolimus maintenance dose was significantly higher in those with CYP3A5*1/*1 than CYP3A5*1/*3 and CYP3A5*3/*3 variants in the maintenance phase for both formulations. It is also interesting to note that those with CYP3A5*3/*3 demonstrated significantly higher doseadjusted C0 with the Advograf formulation. Our study found that a significantly lower C0 was observed when patients were switched to Advograf. This is similar to findings from other studies on different populations, such as the Dutch, Spanish, and Chinese populations [15,21e23]. In contrast, a cross-over pharmacokinetic study of the 2 formulations performed in the United States showed an increase in C0 with Advograf [14], whereas other comparative pharmacokinetic studies performed in other major European countries and Australia demonstrated that the measurements of C0 were similar for both formulations over a 6- to 8-week study period [6,9]. Most of these studies were designed as industry-sponsored initiative, crossover replication pharmacokinetic studies. Ours was a pharmacokinetic study in which patients were switched from Prograf to Advograf, which was based on real clinical practice. It may also be possible that the lower C0 observed in our study was intentional to maintain the target C0 levels given that there was also a concurrent reduction of
Table 3. Summary of Association Between Different CYP3A5 Variants With Ratio of Conversion and Changes in Dose and Trough Level of Tacrolimus Formulations Patient
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Variants
CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*3/*3 CYP3A5*1/*1 CYP3A5*1/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3 CYP3A5*3/*3 CYP3A5*1/*3
Ratio of Dose of Reduction/ Trough of Reduction/ Conversion Increment (%) Increment (%)
1:1 1:0.6 1:1 1:1 1:1.8 1.7:1 1.4:1 1.2:1 1:1 1:1 1.5:1 1:1 1.1:1 3.5:1 1:1.3 1.3:1 1.2:1 1:1.6 1:1.1 1:1 1.2:1 1:1 1:1 1:1 2:1 1:1 1.3:1 1.2:1
0 (No change) Y44 0 (No change) 0 (No change) [44 Y40 Y26 Y17 0 (No change) 0 (No change) Y33 0 (No change) Y12 Y71 [33 Y20 Y17 [60 [7 0 (No change) Y17 0 (No change) 0 (No change) 0 (No change) Y50 0 (No change) Y20 Y14
Y31 [16 Y12 Y18 Y9 Y17 Y25 Y26 Y15 Y14 Y3 Y45 Y22 [37 Y17 Y2 Y54 Y22 Y24 Y20 Y28 Y18 Y17 Y32 0 (No change) Y29 Y39 Y31
the maintenance dose. The C0 of tacrolimus in our study was in the lower range of the recommended target, probably because the study population consisted mainly of low-risk patients (panel-reactive antibodies [PRA] <10% at transplantation, no acute rejection episodes in >12 months, and no previous graft loss for immunologic reasons prior to participation in the study). Nevertheless, the no biopsyproven acute rejection rate suggested that the lower C0 of tacrolimus as a surrogate of exposure was sufficient to avoid rejection episodes. Lower doses of tacrolimus were required when patients were switched to Advograf in our population. This is in contrast to a 12-week clinical study in a stable Chinese population that reported a significant escalation of dose after 8 weeks of conversion to Advograf to achieve similar C0 [24]. Another study in a Spanish population also showed an increase in dose in Advograf formulations [13]. Our study followed patients for 6 months postconversion, which provided a reasonable period of observation that could possibly explain the differing result. The conversion ratios used in the present study ranged between 1:0.6 mg and 1:3.5 mg, which were wider compared with the study in the Chinese population (1:1 mg) [24]. Another important contributory factor may be drug interactions, with corticosteroid
CYP3A5 GENETIC POLYMORPHISM
85
Table 4. Summary of Whole-Blood Tacrolimus Pharmacokinetic Parameters of Renal Transplant Recipients Before and After Switch From Prograf to Advograf Treatment in Different Variants of CYP3A5 Whole-Blood Tacrolimus Pharmacokinetic Parameters Characteristics
Prograf Mean SD
Advograf Mean SD
Tacrolimus trough level (ng/mL) CYP3A5*1/*1 6.32 0.83 5.57 0.40 CYP3A5*1/*3 6.41 1.61 5.07 1.02 CYP3A5*3/*3 5.96 2.03 4.61 1.14 P (high- vs intermediateNS NS vs low-expressive) Tacrolimus dose (mg/d) CYP3A5*1/*1 6.20 2.97 5.10 1.52 CYP3A5*1/*3 4.39 1.69 4.27 1.74 CYP3A5*3/*3 3.01 1.35 2.17 0.76 P (high- vs intermediate.008 <.001 vs low-expressive) Relative tacrolimus dose (mg/[kg/d]) CYP3A5*1/*1 0.11 0.06 0.08 0.02 CYP3A5*1/*3 0.07 0.03 0.07 0.03 CYP3A5*3/*3 0.04 0.02 0.03 0.01 P (high- vs intermediate.003 <.001 vs low-expressive) Dose-adjusted trough level of tacrolimus (ng.kg.day/mg.mL) CYP3A5*1/*1 74.89 42.79 77.81 27.55 CYP3A5*1/*3 106.23 57.73 87.52 47.72 CYP3A5*3/*3 169.50 99.89 156.94 50.81 P (high- vs intermediateNS .002 vs low-expressive)
Fig 2. Comparison of whole-blood dose-adjusted level of renal transplant recipients before and after switch from Prograf to Advograf treatment in different variants of CYP3A5 Note: Data were presented as mean SD. CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediate-expressive genotype; CYP3A5*3/*3, low-expressive genotype.
having an influence on pharmacokinetics of tacrolimus even at a low dose [25]. Wu et al (2013) reported that corticosteroid was discontinued 1 year after transplantation in the Chinese study [15]. In our study population, corticosteroid was part of the triple regimen throughout the study period.
In addition, the calculation of dose requirement differs according to body weight (mg/kg/d). However, the body mass indexes in our population and the Chinese populations were quite similar (24.9 6.0 vs 24.6 3.0). In addition, 19% of retransplantation patients were included in the Spanish study. The prevalence of expressive-genotype in our population reveals a reliable genotypeephenotype association across a wide range of ethnic and geographically different populations: CYP3A5*1/*1 (4%), CYP3A5*1/*3 (9%), and CYP3A5*3/*3 (15%) [19]. This distribution is consistent with another study on renal transplant recipients conducted in Taiwan [26]. For both formulations, this study demonstrated that patients with CYP3A5*3/*3 required significantly lower daily maintenance doses as demonstrated by higher tacrolimus daily dose requirements and lower relative tacrolimus dose to reach desired C0 when compared
Fig 1. Comparison of whole-blood trough level of renal transplant recipients before and after switch from Prograf to Advograf treatment in different variants of CYP3A5. Note: Data were presented as mean SD. CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediate-expressive genotype; CYP3A5*3/*3, low-expressive genotype.
Fig 3. Comparison of whole-blood daily maintenance dose (mean SD) of renal transplant recipients before and after switch from Prograf to Advograf treatment in different variants of CYP3A5 Note: CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediate-expressive genotype; CYP3A5*3/*3, low-expressive genotype.
Note: CYP3A5*1/*1, high-expressive genotype; CYP3A5*1/*3, intermediateexpressive genotype; CYP3A5*3/*3, low-expressive genotype.
86
with those with CYP3A5*1/*1 or CYP3A5*1/*3. This is consistent with other studies across a range of adult populations in Germany and France following conversion or comparable pharmacokinetic study [27,28]. Increased activity in hepatic CYP3A5 microsomal enzymes caused by the presence of a CYP3A5*1 allele leads to rapid drug clearance and hence higher dose requirements are needed [29]. Interestingly, compared with the patients with CYP3A5*1/*1 genotype, the average dose-adjusted C0 of tacrolimus was significantly higher in patients with CYP3A5*1/*3 or CYP3A5*3/*3 genotypes for both formulations. This is consistent with the findings by Hamzah et al that have shown that CYP3A5 polymorphisms significantly impact tacrolimus C0 in the Malaysian renal transplantation population [30]. However, the study by Hamzah et al was focused on the twice-daily tacrolimus formulation, Prograf. Advograf is a prolonged-release tacrolimus formulation that is released slowly but distributed further in the tissues of stomach, jejunum, and ileum [10]. A wide interindividual expression of CYP3A5 messenger RNA, which influences the protein translation in each of these tissues in the gastrointestinal tract [31], would have significant impact on the differences of its pharmacokinetics compared with Prograf formulations. Interestingly, compared with our study, the mean tacrolimus C0 was no longer significant among variants after 3 months posttransplantation but, similarly, the overall dose-adjusted levels were nearly 2-fold higher in CYP3A5*3/*3 genotypes than in CYP3A5*1/*1 genotypes in the Korean population [32]. This study has several strengths. This study added valuable insight into the influence of CYP3A5 polymorphism on the pharmacokinetics of tacrolimus of different formulations in the South East Asian population. This population differs genetically from the white and African population in which most other studies are based. Clinical factors, such as time from transplantation, patient age and race, food administration, Alb and Hct values, liver function, gastrointestinal motility, and concomitant medication, which could affect the pharmacokinetics of tacrolimus [10], were monitored as best that we could. The use of validated assay methods in determining tacrolimus concentrations ensures accurate measures of systemic exposure. In addition, the 6month preconversion and postconversion period of observation is adequate to show the differences in tacrolimus formulation pharmacokinetics. The relatively small patient population of this study may have limited our ability to detect a biologically meaningful difference. This is due to the fact that Advograf has only recently become available in Malaysia, and patients have been slowly switched to this formulation. However, our center has the highest number of patients on this new formulation compared with other centers caring for renal transplantation patients in Malaysia. It is of interest to note that despite the small number of patients, we were able to demonstrate significant differences in the pharmacokinetic profiles as well as the association between CYP3A5 and
MAC GUAD, ZAHARAN, CHIK ET AL
dose requirements. Our patients were switched to Advograf without washout periods. The lack of washout periods between formulations may have resulted in carryover effects. Furthermore, patients or their caretakers were advised to take the medication before their meal but we cannot exclude if some did not adhere to this instruction, which could affect the overall drug exposure [12]. Due to the nature of our population, which consists of several ethnicities, a small number of patients were pooled together and the effect of CYP3A5 in each ethnicity could not be examined. In addition, there is a variation in the duration of transplant before switching of tacrolimus formulations. This may induce great variability in the C0 because the dose adjustment depends over time on the clinician evaluations and TDM result. This study only focused on CYP3A5, whereas other polymorphisms such as hepatic cytochrome CYP3A4 gene and drug transporter MDR1 gene were not investigated. In summary, this is the first study conducted in a heterogenous group of stable Malaysian renal transplant recipients that showed that the requirement for daily maintenance dose of tacrolimus differed between CYP3A5 variants in which daily maintenance dose was higher in those with CYP3A5*1/*1 variants. In addition, those carrying CYP3A5*3/*3 demonstrated significantly higher doseadjusted C0 with Advograf. As our hospitals are in the phases of converting renal transplant recipients to the more convenient Advograf formulations, the identification of CYP3A5 polymorphism would be a useful way to optimize personalized immunosuppressive therapy of tacrolimus before conversion to minimize the risk for undertherapeutic or overtherapeutic regimens and to avoid incidence of chronic rejection associated with long-term outcome of renal allografts in our renal transplant recipients. ACKNOWLEDGMENTS We gratefully acknowledge the patients for their participation in this study, as well as the staff nurses and transplantation team of the hospital for their assistance in recruiting the patients.
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