Factors affecting the long-term response to tacrolimus in renal transplant patients: pharmacokinetic and pharmacogenetic approach

The Effect of Enalapril, Losartan, or Not Antihypertensive on the Oxidative Status in Renal Transplant Recipients

The clinical and biochemical improvement observed in kidney transplant (RT) recipients is remarkable. The correct functioning of the allograft depends on various factors such as the donor's age, the alloimmune response, the ischemia-reperfusion injury, arterial hypertension, and the interstitial fibrosis of the allograft, among others. Antihypertensive drugs are necessary for arterial hypertension patients to avoid or reduce the probability of affecting graft function in RT recipients. Oxidative stress (OS) is another complex pathophysiological process with the ability to alter posttransplant kidney function. The study's objective was to determine the effect of the administration of Enalapril, Losartan, or not antihypertensive medication on the oxidative state in RT recipients at the beginning of the study and one year of follow-up. All patients included in the study found significant overexpression of the oxidative damage marker to DNA and the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx). In contrast, it was found that the determination of the total antioxidant capacity decreased significantly in the final determination at one year of follow-up in all the patients who ingested Enalapril and Losartan. We found dysregulation of the oxidative state characterized mainly by oxidative damage to DNA and a significant increase in antioxidant enzymes, which could suggest a compensatory effect against the imbalance of the oxidative state.

LCPT once-daily extended-release tacrolimus tablets versus twice-daily capsules: a pooled analysis of two phase 3 trials in important de novo and stable kidney transplant recipient subgroups

African-American and elderly kidney transplant recipients (KTR) have increased risk for poor clinical outcomes post-transplant. Management of immunosuppression may be challenging in these patients and contribute to worse outcomes. A novel once-daily formulation of tacrolimus (LCPT) has demonstrated noninferiority, similar safety, improved bioavailability, a consistent concentration time profile, and less peak and peak-trough fluctuations vs. tacrolimus twice-daily (Tac BID). This pooled analysis of two phase 3 randomized, controlled trials, including 861 (LCPT N = 428; Tac BID N = 433; 38% of patients were stable KTR, and 62% were de novo KTR) patients, examined the efficacy of LCPT in KTR subgroups (blacks, females, and age ≥65). Overall, treatment failure [death, graft failure, centrally read biopsy-proven acute rejection (BPAR), or lost to follow-up] at 12 months was as follows: LCPT: 11.9%, BID Tac: 13.4% [-1.48% (-5.95%, 2.99%)]. BPAR rates were as follows: LCPT: 8.2%, Tac BID: 9.5% [-1.29% (-5.14%, 2.55%)]. Numerically, fewer treatment failure events with LCPT were found in the majority of subgroups, with significantly less treatment failure associated with LCPT among black KTR [-13.82% (-27.22%, -0.31%)] and KTR ≥65 [-13.46% (-25.27%, -0.78%)]. This pooled analysis suggests numerically lower efficacy failure rates associated with LCPT among high-risk subgroups, in particular black KTR and KTR ≥65 years old.

Frequency of CYP450 enzyme gene polymorphisms in the Greek population: review of the literature, original findings and clinical significance

The cytochrome P450 (CYP450) enzyme family is involved in the oxidative metabolism of many therapeutic drugs and various endogenous substrates. These enzymes are highly polymorphic. Prevalence of CYP450 enzyme gene polymorphisms vary among different populations and substantial inter- and intra-ethnic variability in frequency of CYP450 enzyme gene polymorphisms has been reported. This paper provides an overview and investigation of CYP450 genotypic and phenotypic reports published in the Greek population.

Pharmacokinetics in stable kidney transplant recipients after conversion from twice-daily to once-daily tacrolimus formulations

BACKGROUND

A prolonged-release formulation of tacrolimus for once-daily administration (Tacrolimus QD) has been developed to offer potential improvements in patient adherence. This study compared the pharmacokinetics (PK) of tacrolimus in stable kidney transplant recipients before and after conversion from twice-daily tacrolimus (Tacrolimus BID) to Tacrolimus QD.

METHODS

This was an open-label, multicenter replicate design study in stable adult kidney transplant recipients (≥6 months posttransplantation) maintained on Tacrolimus BID. Patients underwent four sequential 14-day treatment periods of alternating Tacrolimus BID and QD (mg:mg conversion). Four 24-hour PK profiles were collected, one on the last day of each treatment period. Adverse events were also reported.

RESULTS

A total of 60 of 69 patients completed all 4 PK profiles. Steady-state tacrolimus area under the curve from 0 to 24 hours and Cmin were comparable for both formulations, with treatment ratio means (90% confidence intervals) of 92.9% (89.8%-96.0%) and 90.9% (87.3%-94.6%), respectively (acceptance interval: 80%-125%). Both formulations were well tolerated, with renal function remaining stable over the 8-week period. There was a good correlation between area under the curve from 0 to 24 hours and Cmin for Tacrolimus QD and BID (r = 0.88 and 0.82, respectively). The relationship between these two parameters was also similar.

CONCLUSIONS

The results of this study provide evidence for safe conversion from Tacrolimus BID to QD with appropriate trough concentration monitoring.

Gender differences in pharmacokinetics of tacrolimus and their clinical significance in kidney transplant recipients

BACKGROUND

The possible influence of gender on tacrolimus disposition and response in kidney transplant recipients is an issue of medical importance.

OBJECTIVE

The aim of this study was to detect interpatient pharmacokinetic variability of tacrolimus due to patients' gender and to assess the predictability of individual tacrolimus concentrations using abbreviated AUC measurements. The secondary objective was to find the best sampling time to predict the exposure of tacrolimus in kidney transplant recipients.

METHODS

Gender-related first oral dose tacrolimus pharmacokinetics studies were conducted in 20 Serbian kidney transplant recipients (10 men/10 women) on quaternary immunosuppressive therapy. The first tacrolimus oral dose (0.05 mg/kg) was given on day 5 post-transplant. Blood concentrations were measured by microparticle enzyme immunoassay method. Associations between each sampling time point of concentrations and 12 hours after the administration AUC (AUC(0-12)) were evaluated by Pearson correlation coefficients. Abbreviated sampling equations were derived by multiple stepwise regression analyses.

RESULTS

AUC(0-12) showed remarkable interindividual variations after the first tacrolimus oral dose. There were significantly lower values of AUC in women than men (P < 0.05). The most important time point influencing AUC(0-12) was the concentration of tacrolimus measured 2 hours after administration(C(2)) in women, whereas in men the most important time points were the concentrations at 1 (C(1)), 4 (C(4)), and 12 (C(12)) hours as an abbreviated AUC.

CONCLUSION

Our results show significant differences between men and women. C(2) seems to be indicator of total body exposure to tacrolimus in the early period after kidney transplant in women. The three-point sampling method seems to be a good indicator of abbreviated AUC for a tacrolimus monitoring strategy in men.

Toward personalized medicine in renal transplantation

BACKGROUND

The pharmacokinetics of tacrolimus (TRL) are clearly affected by genetic polymorphisms in drug-metabolizing enzymes, which lead to large interindividual differences in dose-response relations. In addition, TRL has a narrow therapeutic index requiring monitoring of blood levels. The objective of the present observational, retrospective study was to associate maintenance TRL doses with various genetic markers seeking to guide optimization of the initial dose.

METHODS

Results of DNA samples from 15 kidney transplant patients were correlated retrospectively with clinical information from medical records. Samples were genotyped using PHARMAchip. Association studies were performed with χ2 and Pearson tests and by analysis of variance. The study was carried out in accordance with international ethical standards of the Helsinki Declaration and approved by our ethics committee.

RESULTS

Two patient groups were identified to show a difference in TRL dose requirements: a control (0.014-0.10 mg/kg/per day) and an high-dose group (0.14-0.15 mg/kg/per day). The presence of CYP3A5*1 and the null allele in GSTM1 were significantly associated (P=.01 and P=.04) with the need for higher immunosuppressive doses (>0.10 mg/kg/per day). There were no differences in plasma levels of TRL or other clinical variables between the patient groups.

CONCLUSION

Determination of the CYP3A5 genotype might be used to predict initial TRL requirements, although other genetic variants also provide important information to adjust the drug dose.

Tacrolimus dosing in Chinese renal transplant recipients: a population-based pharmacogenetics study

OBJECTIVES

The aims of this study were to examine the effects of genetic and clinical factors on the maintenance dose of tacrolimus in patients following renal transplantation and to develop a tacrolimus-dosing model that could be combined with associated factors.

PATIENTS AND METHODS

This study included 142 renal transplant recipients who received tacrolimus as immunosuppressive agent. CYP3A5, MDR1 and NR1I2 gene polymorphisms were identified based on the SNaPshot assay. The relationship between the genetic and clinical factors and tacrolimus maintenance dose as well as between dose-corrected tacrolimus concentration was examined.

RESULTS

CYP3A5 genotype, body weight, haematocrit, haemoglobin and total bilirubin significantly influenced the maintenance tacrolimus dose. The tacrolimus-dosing model derived from linear regression model accounted for 40.5% of total variations in the tacrolimus maintenance dose.

CONCLUSIONS

A pharmacogenetics-based dosing model has been developed for the prediction of the tacrolimus maintenance dose in renal transplant recipients. This model may be useful in helping clinicians prescribe the initial tacrolimus dose with greater safety and effectiveness.