Higher Concentrations of Cyclosporine Metabolites in Liver Transplant Recipients With a History of Viral and Bacterial Infections.

BACKGROUND: Infection remains a serious clinical problem in liver transplant (LTX) recipients. A higher risk of infection is connected with immunosuppression therapy. The aim of the study was to assess the relationships between infections' incidence and concentrations of cyclosporine (CsA) metabolites after LTX. METHODS: Forty-three liver transplant recipients receiving CsA were included in the study. With the use of liquid chromatography combined with tandem mass spectrometry, concentrations of CsA and its metabolites were measured: dihydroxylated cyclosporine metabolites (DiHCsA), trihydroxylated cyclosporine metabolites (TriHCsA), demethylcarboxylated cyclosporine metabolites (DemCarbCsA), AM1, AM9, and AM4N. The study protocol conformed with the Declaration of Helsinki. RESULTS: Patients with a history of Epstein-Barr virus (EBV) infection had higher DiHCsA, TriHCsA, DemCarbCsA, AM1/CsA, DiHCsA/CsA, TriHCsA/CsA i DemCarbCsA/CsA in comparison with group without such infection (P = .049, P = .037, P = .006, P = .018, P = .005, P = .027, and P = .026, respectively). LTX recipients with a history of all viral infections had higher DiHCsA, TriHCsA, DiHCsA/CsA, TriHCsA/CsA than patients without viral infections (P = .013, P = .021, P = .013, and P = .048, respectively). Multivariable analysis showed that AM1, DiHCsA, TriHCsA, DemCarbCsA, AM4N/CsA had positively influence on the incidence of all viral infections (ß = 0.0302, P = .0328; ß = 0.0699, P = .0453; ß = 0.6781, P = .0382; ß = 0.6767, P = .0414; and ß = 0.8307, P = .0267, respectively). In multivariable analysis, patients with a history of all bacterial infections had higher AM1 and higher AM1/CsA in comparison with LTX recipients without such infections (ß = 0.0118, P = .0279; and ß = 0.0099, P = .036, respectively). CONCLUSION: In liver transplant recipients with a history of viral or bacterial infections higher concentrations of CsA metabolites were found. Possibly CsA metabolites could be used to assess the risk of infection in patients after liver transplantation. It should be confirmed in further investigations.

Lack of Relationship Between Renal Function and Genetic Variants of CYP3A4, CYP3A5, MDR1, MRP2, UGT1A9, UGT1A8, and UGT2B7 in Patients After Liver Transplantation in a 2-Year Follow-up.

BACKGROUND: The prolonged survival time after liver transplantation (LTX) creates the possibility of the occurrence and development of complications in the late post-transplantation period. Deterioration of renal function is 1 of these complications. The nephrotoxicity of calcineurin inhibitors (CNIs) and their metabolites produced during pharmacokinetic processes in the body is also postulated. The study was aimed at assessment of the relationship between selected single gene polymorphisms (SNPs) for enzymes and transport proteins and change of estimated glomerular filtration rate (ΔeGFR) during 2-year follow-up in LTX patients. METHODS: The study involved 244 patients after LTX (105 women [43.0%] and 139 men [57.0%]) receiving tacrolimus (191; 78.3%) or cyclosporine A (53; 21.7%). The study protocol conforms with the Declaration of Helsinki. RESULTS: We have not observed significant differences of ΔeGFR between groups distinguished based on analyzed genotypes in patients treated with cyclosporine or tacrolimus. CONCLUSION: Genetic variations of CYP3A4, CYP3A5, MDR1, MRP2, UGT1A9, UGT2B7, and UGT2B7 tested in LTX recipients are not associated with kidney function during the 24-month follow-up.

Worsening of Kidney Transplant Function During 2-Year Follow-up Is Associated With the Genetic Variants of CYP3A4, MDR1, and UGT1A9.

BACKGROUND: Calcineurin inhibitors (CNIs), tacrolimus and cyclosporine, undergo pharmacokinetic processes. Enzymes and transport proteins found in various organs are involved. It is possible that genetic polymorphisms of these proteins influence CNIs pharmacokinetics and the generation of CNIs metabolites. CNIs may be nephrotoxic, and it is thought that some CNIs' metabolites may have a similar effect. The study was aimed at the assessment of the relationship between selected gene polymorphisms for enzymes and transport proteins and change of estimated glomerular filtration rate (eGFR) during a 2-year follow-up in kidney transplant (KTX) patients. METHODS: The study involved 366 patients after KTX (160 women; 43.7%) receiving tacrolimus (62.57%) and cyclosporine (37.43%). The mean age was 50.1 years, and the median time after KTX was 60.5 months. The study protocol conformed with the Declaration of Helsinki. The percent of difference between eGFR at baseline and at 24 months (ΔeGFR) was calculated. We evaluated selected genetic polymorphisms of CYP3A4, CYP3A5, MDR1, UGT1A9, UGT2B7, UGT1A8, and MRP2. RESULTS: In the tacrolimus group, there were no significant differences of ΔeGFR between groups distinguished based on analyzed genotypes. In the cyclosporine group, differences were found for CYP3A4∗22 C/C -12.3 (-26.8 to -1.8) versus C/T 13.2 (12.4 to 13.9), P = .034; MDR1 3435C>T C/T -18.2 (-31.5 to -5.7) versus C/C -1.8 (-17.1 to 6.9) vs T/T -8.1 (-18.4 to 12.4), P = .031; and UGT1A9 2152C>T C/C -9.0 (-25.5 to 2.8) versus C/T -26.8 (-31.9 to -24.1), P = .017. CONCLUSION: The study results suggest that in KTX metabolic transformations and transport, especially of cyclosporine, dependence on the genetic variability of CYP3A4, UGT1A9, and MDR1 may contribute to kidney damage.

Plasma microRNA-126-3p and neutrophil-to-lymphocyte ratio in patients with chronic kidney disease: relationships to ambulatory 24-h blood pressure.

Pro-inflammatory milieu of chronic kidney disease (CKD) results in endothelial damage and contributes to increased cardiovascular risk. The aim of the study was to evaluate association between neutrophil-to-lymphocyte ratio (NLR) and plasma relative expression of endothelially abundant miR-126-3p with circadian blood pressure (BP) pattern in CKD patients. This single-center observational study involved CKD stage 1-5 patients and healthy age- and sex-matched control subjects. All study participants had 24-h automatic blood pressure measurement (ABPM) performed. Plasma miRNA was quantified by qRT-PCR, in relation to endogenous U6 snRNA. In total, 90 CKD patients (60 ± 14 years, 52% males, 33 renal transplant recipients) and 25 healthy control subjects (55 ± 13 years, 48% males, p > 0.05) were enrolled in the study. We observed a positive correlation between miR-126-3p and average nighttime SBP (rho = 0.27, P = 0.02), average nighttime DBP (rho = 0.32, P = 0.003), night-day SBP ratio (ND-SBP), rho = 0.23, P = 0.03 and night-day DBP ratio (ND-DBP), rho = 0.26, P = 0.02. A positive association was found between NLR and average nighttime SBP (rho = 0.25, P = 0.01), ND-SBP (rho = 0.26, P = 0.006), and ND-DBP (rho = 0.28, P = 0.03). In the multiple regression model, NLR remained an independent predictor of average nighttime SBP (Beta per log change of NLR [95% CI]: 11.2 [1.8-10.6], P = 0.02), whereas miR-126-3p of nighttime DBP (1.88 [0.48; 3.28], p = 0.009), The results of our study point towards a link between both NLR and miR-126-3p and nighttime hypertension in CKD patients.

Dose-adjusted and dose/kg-adjusted concentrations of mycophenolic acid precursors reflect metabolic ratios of their metabolites in contrast with tacrolimus and cyclosporine.

BACKGROUND AND PURPOSE: Therapeutic drug monitoring is a valuable tool supporting immunosuppressive therapy. Significant variation of immunosuppressive drug (ISD) concentrations during their use at similar doses is the basis of dose-normalization strategy. The strategy of dose-adjustment is proposed to identify variability in the rate of ISD metabolism. While the parent drug-to-metabolite ratio (metabolic ratio, MR) represents the rate of formation of individual metabolites. The present study was aimed at evaluation of associations between ISDs' metabolism rate expressed as dose-adjusted concentrations (C/D) and dose/kg-adjusted concentrations (C/D/kg) and MRs of individual metabolites of tacrolimus, cyclosporine A and MPA precursors. EXPERIMENTAL APPROACH: 506 patients have participated: 284 males (56.13%) and 222 females (43.87%); 318 after kidney (62.85%) and 188 after liver transplantation; median age was 51.34 (39.32-59.95) years and median time after transplantation 78.92 (33.87-138.4) months. KEY RESULTS: Generally, we have not observed significant relationships between dose-adjusted and dose/kg-adjusted concentrations and MRs of cyclosporine and tacrolimus. Significant correlations were found for: AM9/CsA and dMC-CsA/CsA in kidney transplant recipients and MIII/Tac, AM1/CsA and AM4N/CsA in liver transplant recipients. In contrast, MRs of mycophenolic acid (MPA) metabolites correlated significantly with MPA C/D and C/D/kg both in kidney and liver transplant recipients. CONCLUSION AND IMPLICATIONS: In conclusion, easily available and easy to use in clinical practice C/D and C/D/kg ratios cannot be considered as parameters directly reflecting the rate of generation of major metabolites of cyclosporine and tacrolimus both in liver and kidney transplant recipients.

Cyclosporine Metabolites' Metabolic Ratios May Be Markers of Cardiovascular Disease in Kidney Transplant Recipients Treated with Cyclosporine A-Based Immunosuppression Regimens.

Cardiovascular disease (CVD) remains one of the primary causes of death after kidney transplantation (KTX). Cyclosporine (CsA) metabolites may play a role in CVD. Metabolic ratio (MR) may be considered a measure of intra-individual differences of CsA metabolism. The study was aimed at analysis of associations of CVD with indices of CsA metabolism: MRs and dose-adjusted CsA concentrations (C/D and C/D/kg). The study was performed in the Department of Immunology, Transplant Medicine, and Internal Diseases of the Medical University of Warsaw and involved 102 KTX recipients. Whole blood concentrations of cyclosporine A, AM1, AM9, AM4N, demethylcarboxylated (dMC-CsA), dihydroxylated (DiH-CsA), trihydroxylated (TriH-CsA) cyclosporine metabolites were determined by liquid chromatography coupled with tandem mass spectrometry. Lower AM9/CsA were observed in diabetics. Patients with coronary disease and/or myocardial infarction had lower dMC-CsA/CsA and higher AM4N/CsA. Supraventricular arrhythmia (SVA) was associated with higher AM1/CsA and AM4N/CsA. Hypertriglyceridemia (hTG) was associated with lower AM9/CsA, higher C/D and C/D/kg. Decrease of AM9/CsA and AM4N and higher D/C were associated with overweight/obesity. Systolic blood pressure (BP) positively correlated with dMC-CsA/CsA and negatively with C/D/kg. Diastolic BP correlated positively with AM1/CsA, dMC-CsA/CsA, DiH-CsA/CsA and TriH-CsA/CsA. We have demonstrated the association of coronary disease/myocardial infarction, SVA, hTG, overweight/obesity and elevated arterial BP with higher MRs of AM1, AM4N, dMC-CsA, DiH-CsA and TriH-CsA, and lower MRs of AM9, which may indicate deleterious and favourable effects of individual CsA metabolites on cardiovascular system and suggest engagement of specific enzymatic pathways.

CXCL12 in Patients with Chronic Kidney Disease and Healthy Controls: Relationships to Ambulatory 24-Hour Blood Pressure and Echocardiographic Measures.

BACKGROUND/AIMS: Chronic kidney disease is a pro-inflammatory condition where the interplay between different regulatory pathways and immune cells mediates an unfavorable remodeling of the vascular wall and myocardial hypertrophy. These mechanisms include the action of CXCL12. The aim of this study is to evaluate the association between serum CXCL12 with left ventricular hypertrophy (LVH) and blood pressure control in chronic kidney disease (CKD) patients. METHODS: This single-center observational study involved 90 stable CKD stage 1-5 patients (including 33 renal transplant recipients) and 25 healthy age- and sex-matched control subjects. CXCL12 was quantified by ELISA. 24-h ambulatory blood pressure monitoring was performed in 90 patients and 25 healthy controls. Left ventricular mass index (LVMI) was calculated based on the transthoracic echocardiography measurements in 27 patients out of the CKD population and in the whole control group. RESULTS: CXCL12 correlated significantly with LVMI by multivariate regression analysis (coefficient B = 0.33, p = 0.02) together with age (B = 0.30, p = 0.03) and gender (B = 0.41, p = 0.003). A positive correlation was observed between CXCL12 and average 24-h systolic blood pressure (SBP) (rho = 0.35, p = 0.001), daytime SBP (rho = 0.35, p = 0.001), and nocturnal SBP (rho = 0.30, p = 0.002). Nocturnal hypertension was frequent (46% of CKD patients). CONCLUSIONS: The results of our study point towards a link between CXCL12 and LVH as well as blood pressure control among patients with CKD, supporting the thesis that CXCL12 may be regarded as a new potential uremic toxin.

Low Transfer of Tacrolimus and Its Metabolites into Colostrum of Graft Recipient Mothers.

Currently, the majority of neonates born to organ recipient mothers on chronic immunosuppressive therapy are formula fed. However, over the past few years, evidence has grown, suggesting that breastfeeding might be possible and beneficial. We designed a study assessing the transfer of tacrolimus into the colostrum of posttransplant mothers. We assessed the amount of tacrolimus and its metabolites, M-1 and M-3, that would be ingested by the breastfed neonates. Concentrations of tacrolimus and its metabolites were measured in colostrum from 14 posttransplant mothers as well as in venous cord blood and venous blood of the neonates. Test material analysis was performed by liquid chromatography coupled with mass spectrometry (LC/MS). The amount of ingested formula was registered, which allowed for estimation of the amount of tacrolimus and its metabolites that would be ingested by breastfed infants. The mean amount of tacrolimus that would be ingested by the neonates in maternal milk was 151.4 ng/kg/24 h (standard deviation SD ± 74.39); metabolite M-1: 23.80 ng/kg/24 h (SD ± 14.53); and metabolite M-3: 13.25 ng/kg/24 h (SD ± 9.05). The peak level of tacrolimus and metabolite M-1 in colostrum was noted 8 h after an oral dose (3.219 ng/mL SD ± 2.22 and 0.56 ng/mL SD ± 0.60, respectively) and metabolite M-3 after 6 h (0.29 ng/mL SD ± 0.22). Low concentrations of tacrolimus and its metabolites, M-1 and M-3, in colostrum show that neonates will ingest trace amounts of the drug. Further studies are required to fully assess the safety of breastfeeding by posttransplant mothers.

Plasma microRNA-155-5p is increased among patients with chronic kidney disease and nocturnal hypertension.

MicroRNAs play multiple roles in the regulation of blood pressure (BP). Nevertheless, to date, no study has assessed the association between microRNA plasma expression and BP control in chronic kidney disease (CKD) patients. Given this background, we evaluated the plasma expression of miR-155-5p, a translational inhibitor of angiotensin receptor type I, in CKD patients, to determine the association between miR-155-5p level and BP control. In this single-center cross-sectional study, we analyzed the miR-155-5p concentration by quantitative reverse transcriptase polymerase chain reaction using the U6 snRNA as a reference gene and 24-hour ambulatory blood pressure monitoring in CKD patients (stage ≥2) in relation to a control group of healthy age-matched and gender-matched individuals, with normal BP proven by the ambulatory blood pressure monitoring. We enrolled a total of 105 patients with CKD (stages 2-5, including 33 kidney renal transplant recipients), aged 59 ± 14 years; 47% males and 26 healthy volunteers (aged 55 ± 13, 50% male). Within the study group, a total of 36 patients (40%) presented with an average 24-hour systolic BP (SBP) ≥130 mm Hg and 41 patients (45%) presented nocturnal hypertension (NHT; SBP ≥120 mm Hg or diastolic BP ≥ 70 mm Hg). miRNA-155-5p was increased in plasma of CKD patients with median expression relative to control subjects equal to 2.92 (1.34-5.58). Interestingly, the plasma miRNA-155-5p expression was significantly higher in patients with NHT: 4.04 (2.92-10.8) versus 2.01 (1.21-3.07), P = .001 and its expression maintained an independent association with the average nocturnal SBP (coefficient B = 4.368, P = .047) by a multivariate regression analysis adjusted for confounders. The miR-155-5p was increased among CKD patients and further increased among subjects presenting with NHT. Further studies are warranted to determine the role of this non-coding RNA as a potential novel biomarker and therapeutic target in the non-dipping CKD individuals, characterized by increased cardiovascular risk.

Immune biomarkers and long­term graft survival: a prospective follow­up of 457 kidney transplant recipients.

INTRODUCTION    Antibodies against donor human leukocyte antigens (HLAs) play a significant role in the pathogenesis of antibody­mediated rejection, although their relevance during the late posttransplant period is unknown. A non­HLA polymorphic antigenic system, like major histocompatibility class I chain­related antigen A (MICA), might be another target for antibody responses involved in rejection. OBJECTIVES    We conducted a 7­year prospective study to determine the effect of positivity for anti­HLA and anti­MICA antibodies on kidney graft survival. PATIENTS AND METHODS    A random blood sample was collected from 457 kidney recipients during a regular outpatient visit. Patients who were less than 6 months after transplantation were excluded. Evaluation of anti­HLA (classes I and II) and anti-MICA antibodies was performed with the use of Luminex assays. An outpatient registry was used to monitor kidney function during a 7­year follow­up. RESULTS    A total of 147 patients (32%) had anti­HLA and 88 patients (19%) had anti­MICA antibodies. Graft failure occurred in 67 anti­HLA­positive individuals (46%) as compared to 81 anti­HLA­negative ones (26%) (P <0.05), and in 30 anti­MICA­positive individuals (34%) as compared to 118 anti­MICA­negative ones (32%) (P = 0.52). Anti­HLA antibodies were associated with increased incidence of graft failure: it was reported in 200 patients with an estimated glomerular filtration rate of more than 30 ml/min/1.73 m2 body surface area more than 5 years after transplantation (P <0.005). CONCLUSIONS    Anti­HLA, but not anti­MICA, antibodies in randomly obtained blood samples were the significant predictor of late kidney graft failure and could be a low­cost method enabling identification of patients requiring an individualized posttransplant approach. The results of our study provide an additional rationale for investigating immune biomarkers in certain diseases.

Mycophenolic Acid Metabolites Acyl-Glucuronide and Glucoside Affect the Occurrence of Infectious Complications and Bone Marrow Dysfunction in Liver Transplant Recipients.

BACKGROUND Mycophenolic acid (MPA) prodrugs are anti-proliferative immunosuppressive agents commonly used after organ transplantation. Although they are generally well tolerated by patients, adverse effects may occur. It is postulated that MPA metabolites could also contribute to these adverse effects. MATERIAL AND METHODS The objective of this study was the assessment of concentrations of total MPA and its metabolites, phenyl glucuronide (MPAG), acyl glucuronide (AcMPAG) and glucoside (GluMPA), using liquid chromatography combined with mass spectrometry (LC/MS/MS) in two groups: kidney transplant recipients and liver transplant patients. Associations of MPA and its metabolites with adverse effects were analyzed. RESULTS The study group consisted of 211 recipients of liver or kidney transplants who received immunosuppressive therapy, including MPA prodrugs. Multivariant analysis showed a positive influence of MPA on gastroenterotoxicity in kidney transplant recipients. In liver patients, gastroenterotoxicity was associated with lower MPAG concentrations. A positive influence of AcMPAG on bacterial infections in liver transplant patients was observed. In liver transplant recipients, a positive influence of MPA and a negative influence of GluMPA levels on the PLT count were revealed. MPA and its metabolites did not influence the hemoglobin levels in both groups. There were no significant relationships among MPA, its metabolites and WBC counts. CONCLUSIONS In kidney transplant recipients, total MPA trough concentration is associated with gastroenterotoxicity and its monitoring could have important role in management of gastrointestinal complications. The quantification of AcMPAG in liver recipients receiving MPA may be helpful in avoiding bacterial infections. GluMPA seems to have a toxic effect on thrombopoiesis.

Anti-HLA and anti-MICA antibodies in liver transplant recipients: effect on long-term graft survival.

OBJECTIVE: Presence of anti-HLA antibodies has a well-known impact on kidney grafts survival; however their role in liver transplantation has not been fully elucidated. We conducted a 7-year prospective study to show correlation between presence of anti-HLA and anti-MICA antibodies and liver graft survival. METHODS: Blood samples from 123 liver transplant recipients were collected during patients routine visits. Time from transplantation to blood sample collection was different for each patient. Blood samples were tested for anti-HLA (separately class I and II) and MICA antibodies using Luminex assays. RESULTS: There were 32 (26%) patients with positive anti-HLA and 37 (30%) with positive anti-MICA antibodies. Graft loss occurred in 7 cases (23%) in anti-HLA positive group compared to 20 (22%) in anti-HLA negative group (P = ns) and in 8 cases (22%) in anti-MICA positive group but 19 (23%) in anti-MICA negative group (P = ns). No correlations were detected between presence of antibodies and acute graft rejection (AGR). Presence of any antibodies (anti-HLA or anti-MICA antibodies) correlated with late graft rejection (P = 0.04). CONCLUSION: Presence of anti-HLA or anti-MICA had no impact on long-term liver graft survival; however, detection of any antibodies was correlated with episodes of late graft rejection.

Two rapid ultra performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) methods with common sample pretreatment for therapeutic drug monitoring of immunosuppressants compared to immunoassay.

Therapeutic drug monitoring of immunosuppressive agents is a critical and essential part of patient therapy after organ transplantation. We have developed high-throughput, robust, and rapid liquid chromatography-tandem mass spectrometry (UPLC/MS/MS) methods with common pretreatment procedures for simultaneous quantification of four immunosuppressive agents (everolimus, sirolimus, tacrolimus, and cyclosporin A) in whole blood and one immunosuppressant (mycophenolic acid) in plasma. The new approach used in this work is based on improved sample preparation procedures allowing the analysis of five immunosuppressive drugs. Whole blood was prepared by transferring 100µL of blood into a 1.5-mL silanized conical test tube. Zinc sulfate solution (150µL), containing deuterated internal standards, was added to perform hemolysis. The samples were vortexing for 10s, followed by the addition of 250µL acetonitrile, containing internal standard for cyclosporin A, to precipitate proteins. The mixture was vortexed for 1min and centrifuged for 2min at 14,000rpm. The whole supernatant was transferred to a vial. To prepare blood plasma, the hemolysis step involving the addition of zinc sulfate was omitted and, instead of acetonitrile, methanol was used as the solvent for the internal standard (mycophenolic acid-d3). The volumes of chemicals used in this procedure were the same as those used in the procedure for immunosuppressants in whole blood. The basic validation parameters for the analytical methods were limits of detection (0.5ng/mL for everolimus, sirolimus and tacrolimus, 25ng/mL for cyclosporin A and 100ng/mL for mycophenolic acid), precision (<15%), recovery (>84%), repeatability and reproducibility. Possible mutual ion suppression was eliminated in the presence of internal standards. The method developed for the quantitation of immunosuppressants in whole blood was used to analyze 276 patient samples containing tacrolimus and 55 samples containing cyclosporin A. The results from LC/MS/MS were compared to those obtained from immunoassays of the same samples. Immunoassays significantly overestimated the concentrations of immunosuppressants.

Impact of CYP3A4*1B and CYP3A5*3 polymorphisms on the pharmacokinetics of cyclosporine and sirolimus in renal transplant recipients.

BACKGROUND: Calcineurin inhibitor (cyclosporine, CsA) and mTOR inhibitors (sirolimus, SRL) - immunosuppressants used to prevent allograft rejection after renal transplantation - have a narrow therapeutic index and show considerable inter-individual pharmacokinetic differences. Differences in expression and activity of cytochrome P450 (CYP) 3A4 and 3A5 affect these pharmacokinetics; cytochrome activity differences are associated with CYP genetic polymorphisms. MATERIAL/METHODS: This study evaluated the effects of polymorphisms in CYP3A4 and CYP3A5 on immunosuppressive drug-dose adjusted trough blood concentrations. One hundred renal transplant recipients were genotyped for CYP3A4*1B and CYP3A5*3 using PCR-RFLP. Blood concentrations of CsA and SRL were determined by EMIT and HPLC/UV, respectively. RESULTS: The allelic frequencies of CYP3A4*1B and CYP3A5*3 in the study group were 2.5% and 96.5%, respectively. The mean cyclosporine dose in CYP3A4*1/*1B subjects was 455.04±128.68 mg/day vs. 261.68±64.72 mg/day in CYP3A4*1/*1 subjects (p<0.001). The mean cyclosporine dose-adjusted trough blood concentrations (ng/ml per mg/kg body weight) in CYP3A4*1/*1B subjects were lower than in the CYP3A4*1/*1 group (37.06±10.38 vs. 44.63±13.99; p<0.218). The mean cyclosporine dose in CYP3A5*1/*3 subjects was 400.65±164.97 mg/day vs. 263.52±64.39 mg/day in CYP3A5*3/*3 subjects (p<0.022). No association was detected between sirolimus trough blood concentration (C0) or dose requirement, and CYP3A4 or CYP3A5 genotype. CONCLUSIONS: Genetic polymorphisms in CYP3A4 and CYP3A5 may underlie inter-individual differences in cyclosporine pharmacokinetics after renal transplantation. Patients with at least 1 functional CYP3A5*1 or CYP3A4*1B allele require significantly higher doses of cyclosporine to reach target drug levels compared to patients with the CYP3A4*1 or CYP3A5*3 alleles.