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I. SURGERY
GENETIC POLYMORPHISM OF CYP3A5 AS A KEY REGULATOR OF PHARMACOKINETICS OF TACROLIMUS IN KIDNEY TRANSPLANT PATIENTS: EVIDENCE IN KAZAKH POPULATION
Baimakhanov B.B., Chormanov A.T., Medeubekov U.Sh., Syrymov Zh.M., Madadov I.K., Dabyltaeva K.S., Belgibaev E.B., Nabiev E.S., Saduakas N.T., Baiyz A.Zh., Aipov B.R.
JSC «National Scientific Center of Surgery named after A.N. Syzganov», Almaty, Kazakhstan
Abstract
Objectives: identification of relationship of CYP3A5 genetic polymorphism with tacrolimus pharmacokinetics in kidney transplant patients in Kazakh population.
Immunosuppressive therapy with the use of tacrolimus is one of the main ones in kidney transplantation. The survival and maintenance of satisfactory graft function in a technically perfect operation depends in most cases on immunological factors. At the same time, there is a question of a personal approach to immunosuppressive therapy of kidney recipients in patients of the Kazakh population before and after surgery. The genetic polymorphism of CYP3A5 is an important link affecting the concentration of tacrolimus and potentially able to predict the optimal dosage of tacrolimus in kidney recipients in the Kazakh population
We examined 80 kidney recipients for the presence of CYP3A5 genetic polymorphism. All the patients studied were selected from the ethnic population. Out of the total number of recipients: 37-men and 43-women. The median age was 37±8 years. All the studied patients underwent a related kidney transplant. The induction was performed using basilixamab or anti-thymocytic globulin (ATG). Immunesupressive regimen was Tacrolimus + Mycophenolic acid + corticosteroids. Postoperatively tacrolimus concentration was taken at 2, 5, 7, 10 and 14th day after the surgery.
БYйрек трансплантациясы бар наукастардагы такролимус фармакокинетикасыньщ непзп реттег^ ретшде CYP3A5 генетикалык полиморфизма казак популяциясындагы деректер
Баймаханов Б.Б., Чорманов А.Т., Медеубеков ¥.Ш., Сырымов Ж.М., Мададов И.К., Дабылтаева К.С., Белпбаев Е.Б., Набиев Е.С., Садуакас Н.Т., Байыз А.Ж., Аипов Б.Р.
«А. Н. Cbi3FaHOB атында?ы Улттык, ?ылыми хирургия орталь™» АК,, Алматы к,., Казахстан
МРНТИ 76.29.62
Baimakhanov B.B.
orcid.org/0000-0002-9839-6853
Chormanov A.T.
orcid.org/0000-0003-3513-1935
Medeubekov U.Sh.
orcid.org/0000-0003-2893-2996
Syrymov Zh.M.
orcid.org/0000-0002-7708-3284
Madadov I.K.
orcid.org/0000-0003-2241-8603
Dabyltaeva K.S.
orcid.org/0000-0003-1226-0005
Belgibaev E.B.
orcid.org/0000-0002-9439-2628 Nabiev E.S.
orcid.org/0000-0002-6167-1962 Saduakas N.T.
orcid.org/0000-0002-5249-1783 Baiyz A.Zh.
orcid.org/0000-0002-6075-2787 Aipov B.R.
orcid.org/0000-0003-2124-0065
Keywords
tacrolimus, kidney transplantation, genetic polymorphism, immuno-suppression
Ацдатпа
Мак,саты: казак популяциясында€ы бYЙрек трансплантациясынан кей1нп наукастардагы CYP3A5 генетикалык, полиморфизм/шц такролимустыц фармакокинетикасымен байланысын аныктау.
Такролимус колдануы иммуносупрессивт терапия бYЙрек трансплантациясыныц непзп эд1стер1шц б1р1 бо-лып табылады. Техникалык туртыда жаксы орындалган операция кезнде трансплантаттыц канагаттанарлык функциясыныц сакталуы жэне кызмет ету\ кеп жагдайда иммунологиялык факторларта байланысты. Бул ретте казак популяциясындагы пациенттерд1ц бYЙрек реципиенттер1н иммуносупрессивт терапиясына отага дей1нп жэне отадан кей1нп кезецдерде дербес кезкарас туралы мэселе туындайды. CYP3A5 генетикалык полиморфизмi такролимус концентрациясына эсер етет1нжэне казак популяциясындагы бYЙрек реципиенттер1нде такролимустыц оцтайлы дозасын болжаут ыктимал кабшет мацызды буын болып табылады.
Б1з CYP3A5 генетикалык полиморфизм/шц болуына бYЙректiц 80 реципиенттер1н зерттед1к. Зерттелген барлык наукастар этникалык популяциялардан тацдалды. Реципиенттердiц жалпы санынан: 37-ерлер жэне 43-эйелдер. Орташа жасы 37±8 жыл болды. Барлык зерттелген наукастарта бYЙрек трансплантациясы жасалды. Индукция базиликсамаб немесе анти-тимоцитарлык глобулин (АТГ) колдану аркылы журпз^. Иммуносупрессивт режим такролимус + микофенол кышкылы + стероидтер болды. Отадан кейнп кезецде такролимус концентрациясыныц 2,5,7,10 жэне 14 к/ндердеп ез^а зерттелдi.
Туйш сездер
такролимус, буйрек трансплантациясы, генетикалык полиморфизм, иммуносупрессия
Генетический полиморфизм CYP3A5 как ключевой регулятор фармакокинетики такролимуса у пациентов с трансплантацией почки: данные в казахской популяции
Ключевые слова
такролимус, трансплантация почки, генетический полиморфизм, иммуносупрессия
Баймаханов Б.Б., Чорманов А.Т., Медеубеков У.Ш., Сырымов Ж.М., Мададов И.К., Дабылтаева К.С., Белгибаев Е.Б., Набиев Е.С., Садуакас Н.Т., Байыз А.Ж., Аипов Б.Р.
АО «Национальный научный центр хирургии им. А. Н. Сызганова», г. Алматы, Казахстан
Аннотация
Цель: выявить взаимосвязь генетического полиморфизма CYP3A5 с фармакокинетикой такролимуса у реципиентов почки в казахской популяции.
Иммуносупрессивная терапия с примененим такролимуса является одной из основных при трансплантации почки. Выживаемость и сохранение удовлетворительной функции трансплантата при технически идеально выполненной операции, зависит в большинстве случаев от иммунологических факторов. При этом встает вопрос о персональном подходе в иммуносупрессивной терапии реципиентов почки пациентов казахской популяции до - и в послеоперационном периодах. Генетический полиморфизм CYP3A5 является важным звеном, влияющим на концентрацию такролимуса и потенциально способным предсказать оптимальную дозировку такролимуса у реципиентов почки в казахской популяции
Нами было исследованно 80 реципиентов почки на наличие генетического полиморфизма CYP3A5. Все исследованные пациенты были выбраны из этнической популяции. Из общего числа реципиентов: 37 - мужчины и 43 - женщины. Средний возраст которых составил 37±8 лет. Всем исследуемым пациентам была выполнена родственная трансплантация почки. Индукция была проведена с применением базиликсамаба или анти-тимоцитар-ного глобулина (АТГ). Иммуносупрессиный режим был по схеме такролимус+микофеноловая кислота+стероиды. В послеоперационном периоде было исследовано изменение концентрации такролимуса на 2,5,7,10 и 14 дни.
Introduction
Kidney transplantation is the most preferable treatment option of terminal chronic kidney disease. The main advantage of kidney transplantation is that graft totally replaces the function of diseased organ. Improvement of the quality of life of patients and return to their daily activities is another great advantage of this option.
Nowadays in Kazakhstan there is an active development of kidney transplantation. One of the most important objectives is to improve the survival rates of graft. With the improvement of donor selection, surgical technique and rational immunosuppressive treatment rates of short-term graft survival greatly increased. For instance, in Kazakhstan 1-year graft survival from living related donor is 91%. Despite these high indicators of 1- year graft survival, 5-year graft survival rates remain to be low. In USA 5-year graft survival from deceased donor is up to 80%, whereas from living donor is from 82 to 90 %, respectively. So it is of paramount interest to improve the rates of long term graft survival [1].
The calcineurin inhibitor tacrolimus are the most widely used immunosuppressive agent. This drug represents a narrow therapeutic index and high inter-individual pharmacokinetic variability, so monitoring its blood level is required to avoid rejection and reduce toxicity [2].
The calcineurin inhibitors tacrolimus is catalyzed by cytochrome P450 CYP3A enzymes. CYP3A4 and CYP3A5 have been identified as the major enzymes
responsible for the metabolism of calcineurin inhibitors in CYP3A subfamilies [3].
The presence of CYP3A4 and CYP3A5 in the intestinal mucosa and in hepatic cells contributes to a first-pass effect as drug molecules are metabolized prior to reaching the systemic circulation. Genetic polymorphism in these 2 enzymes accounts for a significant part of the interindividual variability observed with tacrolimus bioavailability. The best studied genetic variation is in the CYP3A5 gene [4].
The wild-type CYP3A5 *1 allele is associated with greater production of functional CYP3A5 enzyme, thus leading to higher drug-metabolizing activity by CYP3A overall. The CYP3A45*1/*1 genotype increases tacrolimus clearance by 2-fold, while the heterozygous CYP3A5*1/*3 genotype results in approximately 1.7fold greater clearance compared to the CYP3A5*3/*3 population [5-7] CYP3A5 *3/*3 has 48% lower oral clearance compared to CYP3A5 expressers [8].
In this way, we investigated the personalization and rationalization of immunosuppressive treatment. In our country as in whole world genetic factors, determining long-term kidney graft survival, represents a great relevancy in transplantation. The determination of genetic polymorphism of CYP3A5 gives us the opportunity to predetermine the changes in blood concentrations of tacrolimus, better control of immunosuppressive therapy and this will positively affect the long-term graft survival.
The study aimed to determine the significance of CYP3A5 genetic polymorphism in regulation of
tacrolimus pharmacokinetics in kidney transplant patients in Kazakh population.
Material and Methods
We retrospectively studied 80 kidney transplant recipients. Of them - 32 were female and 48 male patients. Mean age 36±12 years old. All patients were selected from Kazakh population and were investigated for CYP3A5 genetic polymorphism (single-nucleotide polymorphism, rs776746, also known as 6986A>G). Patients underwent related living donor kidney transplantation. There were no substantial differences in surgical technique or warm/cold ischemic times. Graft function was immediate in all cases.
Immunosuppression
Induction therapy was either with basiliximab or Anti-Tymocit globulin. Immunosuppressive regimen was Tacrolimus + Mycophenolic acid + corticosteroids.
Tacrolimus concentration was measured by che-miluminescence method. Tacrolimus was administered 0.1 mg/kg/ body weight. Tacrolimus concentration level was taken initially at 2 postoperative days and furtherly at 5th, 7th, 10th and 14th, respectively. Dose addition/reduction was by 1.0 mg. Accepted tacrolimus target level was 10-13 ng/ml.
Statistics
Patients were arranged according to the results by Fisher's test and correlation of graft function and genetic polymorphism of CYP3A5 was assessed Mann-Whitney U test. P < 0.05 was given as significant.
Results
According to the results in our study 61.25% (n=49) of patients were homozygotes, CYP3A5*3*3 carriers (non-expressers) and 38.75% (n=31) were heterozygotes, CYP3A5*1*3 carriers (with one ex-
pressor allele). Patients were arranged by sex/type of polymorphism by Fisher's test. There were no significant differences in sex/CYP3A5 genetic polymorphism in patients Table 1.
Patients were divided into 2 groups: homozygotes and heterozygotes. Tacrolimus concentration was measured on 2, 5th , 7th , 10th and 14th days after surgery and at discharge. There were significant differences in concentrations on 2nd, 5th, 7th and 10th days in both groups (p = 0.02, 0.01, 0.12 and 0.016, respectively). There were no significant statistical differences in tacrolimus concentration on 14 day after the surgery and at discharge (p = 0.085 and 0.171, respectively). In both groups tacrolimus almost reached target level at the end of 2nd week, but in heterozygotes increase was more gradual and predictable rather than in homozygotes (Fig.1). There were no substantial differences in graft function (Table 2). Creatinine level normalized gradually in both groups and there was not significant differences in both groups at discharge (p = 0.834 (Fig.2)
Discussion
Tacrolimus is a commonly used immunosup-pressant after kidney transplantation. It has a narrow therapeutic range and demonstrates wide interindividual variability in pharmacokinetics, leading to potential underimmunosuppression or toxicity. Genetic polymorphism in CYP3A5 enzyme expression contributes to differences in tacrolimus bioavailability between individuals. Individuals carrying one or more copies of the wild-type allele *1 express CYP3A5, which increases tacrolimus clearance. CYP3A5 expressers require 1.5 to 2-fold higher tacrolimus doses compared to usual dosing to achieve therapeutic blood concentrations. Individuals with homozygous *3/*3 genotype are CYP3A5 nonexpressers. CYP3A5 nonexpression is the most frequent phenotype in most ethnic populations,
CYP3A5*1*3 CYP3A5*3*3 p
Female N 13 19
Sex % 42,0% 38,7%
Male N 18 30 1,000
% 58,0% 61,2%
Total % N 31 49
100,0% 100,0%
Table 1.
Arrangement of patients due to gender-CYP genetic polymorphism relationship
■CYP3A5*3*3
•CYP3A5*1*3
Fig. 1
Changes of tacrolimus concentration (ng/ml) with CYP 3A5 genetic polymorphism
2 day 5 day 7 day 10 day
14 day
Discharge
Fig. 2
Changes of creatinine (^mol/l) level in kidney patients with CYP3A5 genetic polymorphism Notes: B - Time before the operation, and D - time at discharge
Table 2.
Changes of Tacrolimus concentration in both groups (Mann - Whitney U test)
-Homozygotes -Heterozygotes
Before the 1 day 3 day 5 day 7 day 9 day At operation discharge
Type of poymorphism 2 day 5 day 7 day 10 day 14 day Discharge
N 31 31 31 31 31 31
Average 5,3 5,2 5,5 6,6 9,0 9,8
CYP3A5*1*3 Std. Deviation 3,0 2,6 1,7 2,2 2,6 1,9
4,4 4,6 5,5 6,8 8,3 9,3
10,2 9,8 6,00 7,90 8,9 5,0
49 49 49 49 49 49
8,3 7,2 7,4 10,1 11,1 11,1
CYP3A5*3*3 St. D 5,2 2,4 2,2 3,9 4,4 2,9
7,1 6,5 6,8 10,0 9,9 11,0
27,0 8,2 8,20 14,10 19,4 13,7
р 0,020 0,010 0,012 0,016 0,085 0,171
except blacks. Differences between CYP3A5 genotypes in tacrolimus disposition have not translated into differences in clinical outcomes, such as acute rejection and graft survival. Therefore, although genotype-based dosing may improve achievement of therapeutic drug concentrations with empiric dosing, its role in clinical practice is unclear [11].
The effect of CYP3A5 *1 and *3 alleles on tacrolimus pharmacokinetics is consistently and extensively documented across a multitude of studies over the past 15 years [9, 10]. The goal of genotype-based dosing is to provide empiric dosing that allows rapid achievement of therapeutic drug concentrations, particularly in the initial days after transplant. In one retrospective study, an empiric weight-based starting dose of 0.1 mg/kg was used to target a therapeutic range of 4-8 mcg/mL [12]. Among CYP3A5 non-ex-pressers (CYP3A5*3/*3), 50% of patients achieved the target range by day 3 of therapy. Among CYP3A5 expressers (CYP3A5*1/*3 or *1/*1), however, only 35.3% of patients achieved through concentrations within the therapeutic range by day 3. Use of therapeutic drug monitoring did allow for rapid dosing correction. By day 7, 64.2% of expressers, compared to 55.4% of non-expressers, achieved therapeutic trough concentrations. These results suggest that CYP3A5 genotyping is likely more useful if available before kidney transplant.
Similar results were received in clinical trial conducted by Quteineh L. and co-authors. In total 136 kidney recipients were studied. As was in previous investigation patients with CYP3A5*1*1 genotype need higher doses of tacrolimus to reach the target concentration. Interestingly the situation remained the same for subsequent 6 and 12 months. CYP3A5 genetic polymorphism was not associated with ta-crolimus nephrotoxicity but influenced the dose adjustment. Authors suggest preoperative evaluation of CYP3A5 genetic polymorphism, especially CYP3A5*1 carriers [13].
In kidney recipients with CYP3A5*1*1 and *1*3, tacrolimus concentration remained low even after dose adjustment in contrast to CYP3A5*3*3 carriers. For instance, half of patients with CYP3A5*1 after 7 days from initiation of immunosuppression tacrolimus was less than 5 ng/ml, whereas in CY-P3A5*3 carriers - more than 20 ng/ml. Thus this genetic factor is one of most important regulators of rational immunosuppressive treatment [14].
Acute rejection episodes were more frequent in expressers, and they may require higher doses of tacrolimus. Similarly, tacrolimus nephrotoxicity was more frequent in non-expressers. Therefore, CYP3A5 polymorphism analysis before renal transplant may help determine the optimal dose of tacro-limus in this population and prevent acute rejection episodes or tacrolimus toxicity [9, 15].
In our clinical study there were not CY-P3A5*1*1 carriers, thus in Kazakh population there are seen only *1*3 and *3*3 genetic polymorphisms. In all cases graft function was immediate. There were not any cases of acute graft rejection in both groups. There was a statistical difference in tacrolimus pharmacokinetics in both groups, but this does not affect graft function and all patients were discharged with good functioning graft. There was also a correlation of tacroli-mus concentration with body mass. So in patients with high body mass index tacrolimus had peak rises up to 20 ng/ml soon after the surgery and subsequently gradual decline. In this patients creatinine level normalized slowly. Tacrolimus didn't have any correlation with age and sex.
Conclusion
It is obvious from received results, that genetic polymorphism of CYP3A5 influences tacrolimus blood concentrations, that appear to be key factor
References
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in immunesupression [16]. Even in rational choice of dose of immunosuppressive agent, genetic factor must be considered as well. In order to improve long-term graft survival rates it is important to maintain therapeutic concentration of tacrolimus in blood. In this way it is important to determine the CYP3A5 genetic polymorphism preoperatively [17], as one of approved genetic determinants of graft survival and for the correct selection of initial dose.
In Kazakh population most patients are non-expressers and this is a national characteristic. Patients reached tacrolimus trough level quickly at low doses. We expect that genotype-based dosing may be the key factor in determination of preferred doses of tacrolimus in each individual. Moreover, genotype-based patterns of dose regimen are now being investigated in order to ease the choice of suitable dose regimen. Rational immunosuppressive treatment leads to prolonged graft function and genetic factors appear to be the key factor in drug dose selection.
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