An open-label, concentration-ranging trial of FK506 in primary kidney transplantation: a report of the United States Multicenter FK506 Kidney Transplant Group

Dynamic effects of CYP3A5 polymorphism on dose requirement and trough concentration of tacrolimus in renal transplant recipients

WHAT IS KNOWN AND OBJECTIVE

Tacrolimus is a widely used immunosuppressive drug with marked pharmacokinetic variability partly due to CYP3A5 polymorphism. Our study aimed to investigate the dynamic effects of CYP3A5 genotypes on dose requirement and trough concentration (C₀ ) of tacrolimus in renal transplant recipients.

METHODS

A total of 194 Chinese renal transplant recipients received oral tacrolimus twice daily. Whole-blood C₀ of tacrolimus were measured on the 3rd day, 7th day, 14th day, 1st month, 3rd month and 6th month post-transplantation. CYP3A5 genotypes were determined and the recipients were categorized as CYP3A5 expressers (CYP3A5*1 allele carriers) and non-expressers (homozygous CYP3A5*3). The correlated serum creatinine, haematocrit and albumin were also detected.

RESULTS

The allele frequencies for CYP3A5*1/*1, *1/*3 and *3/*3 were 7·7%, 44·8% and 47·4%, respectively. There were no significant variability in serum creatinine, haematocrit and albumin values between CYP3A5 expressers and non-expressers. Larger doses were administered to CYP3A5 expressers than to non-expressers after surgery except the initial dose. C₀ were much lower in CYP3A5 expressers than in non-expressers on the 3rd day, 7th day, 14th day and 1st month post-transplantation (P < 0·01); however, no significant differences were found on the 3rd and 6th months post-transplantation. All of the dose-adjusted C₀ in CYP3A5 expressers were significantly lower than non-expressers (P < 0·01). Less of the recipients achieving target C₀ (4-8 ng/mL) were found in CYP3A5 expressers than in non-expressers after initial dose (35·7% vs. 50%). Meanwhile, CYP3A5 non-expressers were detected having higher C₀ (>8 ng/mL) during 3 months post-transplantation. Besides, the proportions in the two groups both increased gradually over time and up to 91·8% and 94% on the 6th month, respectively.

WHAT IS NEW AND CONCLUSION

There are no significant differences in serum creatinine, haematocrit and albumin values between CYP3A5 expressers and non-expressers. CYP3A5 expressers have decreased dose-adjusted tacrolimus C₀ when compared to non-expressers. Dose-adjusted C₀ of tacrolimus increases in a time-dependent manner in both groups.

A preliminary study searching for the right dose of tacrolimus in very young (≤4 years) renal transplant patients

OBJECTIVES

The Radboudumc Amalia Children's hospital in the Netherlands has a programme for renal transplantation in children aged ≤4 years. Children receive chronic corticosteroid sparing immunosuppressive therapy that consists of tacrolimus and mycophenolate mofetil. This work aimed to describe the PK of tacrolimus in children ≤4 years with renal transplants.

METHODS

Paediatric renal transplant patients aged ≤4 years were included in this analysis. A PK curve of tacrolimus recorded ≤3 weeks after transplantation has been standard of care in our institution and aided in adjusting the dose in each patient to attain a target AUC_0-12h of 210 μg h/l early after transplantation.

KEY FINDINGS

Eight patients were included. The first two patients received an initial twice-daily regimen and the subsequent six patients a three-times daily regimen. Median dose-corrected AUC_tau was 63 μg h/l. AUC target attainment was 37.5%. Of the remaining patients, two had an AUC very close to (around 10% below) the target.

CONCLUSIONS

Large interindividual variability of tacrolimus was observed and showed suboptimal AUC target attainment. In this population, an even more aggressive approach of higher doses (e.g. 0.4 mg/kg per day) and more early AUC determination should be considered. This should be evaluated prospectively in a larger group of patients.

The POR rs1057868-rs2868177 GC-GT diplotype is associated with high tacrolimus concentrations in early post-renal transplant recipients

AIM

Cytochrome P450 oxidoreductase (POR) is the only flavoprotein that donates electrons to all microsomal P450 enzymes (CYP), and several POR SNPs have been shown to be important contributors to altered CYP activity or CYP-mediated drug metabolism. In this study we examined the association between 6 POR SNPs and tacrolimus concentrations in Chinese renal transplant recipients.

METHODS

A total of 154 renal transplant recipients were enrolled. Genotyping of CYP3A5*3 and 6 POR SNPs was performed. All patients received a triple immunosuppressive regimen comprising tacrolimus, mycophenolate mofetil and prednisone. Dose-adjusted tacrolimus trough concentrations were obtained on d 7 (C0D7/D) after transplantation when steady-state concentration of tacrolimus was achieved (dosage had been unchanged for more than 3 d).

RESULTS

Tacrolimus C0D7/D in CYP3A5*3/*3/ POR rs1057868-rs2868177 GC-GT diplotype carriers was 1.62- and 2.72-fold higher than those in CYP3A5*3/*3/ POR rs1057868-rs2868177 GC-GT diplotype non-carriers and CYP3A5*1 carriers (220.17±48.09 vs 135.69±6.86 and 80.84±5.27 ng/mL/mg/kg, respectively, P<0.0001). Of CYP3A5*3/*3/ POR rs1057868-rs2868177GC-GT diplotype carriers, 85.71% exceeded the upper limit of the target range (8 ng/mL), which was also significantly higher compared with the latter two groups (14.29% and 0.00%, respectively, P<0.0001). The CYP3A5*3 and POR rs1057868-rs2868177 GC-GT diplotype explained 31.7% and 5.7%, respectively, of the inter-individual variability of tacrolimus C0D7/D, whereas the POR rs1057868-rs2868177 GC-GT diplotype could explain 10.9% of the inter-individual variability of tacrolimus C0D7/D in CYP3A5 non-expressers.

CONCLUSION

The CYP3A5*3 and POR rs1057868-rs2868177 GC-GT diplotype accounted for the inter-individual variation of tacrolimus C0D7/D. Genotyping of POR rs1057868-rs2868177 diplotypes would help to differentiate initial tacrolimus dose requirements and to achieve early target C0 ranges in Chinese renal transplant recipients.

An Evaluation of the Phototoxicity of Tacrolimus (FK506) Ointment in Hairless Mice

The acute phototoxic potential of tacrolimus (FK506) ointment was investigated in Crl:SKH1-hr hairless mice. Response toa series of ultravioletradiation (UVR) site exposures in males (five group) following a single topical administration of tacrolimus ointment (0%[vehicle], 0.03%, 0.1%, 0.3%, 1%, or 3%) indicated that tacrolimus ointment was neither photoprotective or phototoxic. However, a slight but dose-related decrease in body weight relative to the vehicle control was found at the end of the 4-day observation period in the tacrolimus ointment-treated groups. The same concentrations of tacrolimus ointment were applied to the back and sides of mice (five sex group; ∼40% of total body surface area) 5 days week in a 13-week range-finding study to assess the tolerance to the ointment and UVR exposure. Untreated animals served as a control group. Mice were exposed to 72 minutes of UVR from a 6.5-kW xenon lamp. Mortality occurred in the 0.3%, 1%, and 3% ointment groups. Application of 3% tacrolimus ointment was associated with reduced body weight. Mild to moderate erythema and/or edema were noted in all tacrolimus ointment-treated groups. Histopathologi-cal examination indicated a mild increase in the prominence of the stratum granulosum and mild acanthosis of the epidermis in both vehicle-treated and tacrolimus ointment-treated mice. Stomach, esophageal, and/ or abdominal cavity lesions, indicative of systemic toxicity and possibly associated with the in gestion of ointment vehicle during preening, were observed during necropsy. There was minimal photo-mediated dermal toxicity of tacrolimus ointment in the 13 weeks of exposure in the present study.

Improved Tacrolimus Target Concentration Achievement Using Computerized Dosing in Renal Transplant Recipients--A Prospective, Randomized Study

BACKGROUND

Early after renal transplantation, it is often challenging to achieve and maintain tacrolimus concentrations within the target range. Computerized dose individualization using population pharmacokinetic models may be helpful. The objective of this study was to prospectively evaluate the target concentration achievement of tacrolimus using computerized dosing compared with conventional dosing performed by experienced transplant physicians.

METHODS

A single-center, prospective study was conducted. Renal transplant recipients were randomized to receive either computerized or conventional tacrolimus dosing during the first 8 weeks after transplantation. The median proportion of tacrolimus trough concentrations within the target range was compared between the groups. Standard risk (target, 3-7 μg/L) and high-risk (8-12 μg/L) recipients were analyzed separately.

RESULTS

Eighty renal transplant recipients were randomized, and 78 were included in the analysis (computerized dosing (n = 39): 32 standard risk/7 high-risk, conventional dosing (n = 39): 35 standard risk/4 high-risk). A total of 1711 tacrolimus whole blood concentrations were evaluated. The proportion of concentrations per patient within the target range was significantly higher with computerized dosing than with conventional dosing, both in standard risk patients (medians, 90% [95% confidence interval {95% CI}, 84-95%] vs 78% [95% CI, 76-82%], respectively, P < 0.001) and in high-risk patients (medians, 77% [95% CI, 71-80%] vs 59% [95% CI, 40-74%], respectively, P = 0.04).

CONCLUSIONS

Computerized dose individualization improves target concentration achievement of tacrolimus after renal transplantation. The computer software is applicable as a clinical dosing tool to optimize tacrolimus exposure and may potentially improve long-term outcome.

Advances in pharmacotherapy to treat kidney transplant rejection

INTRODUCTION

Current immunosuppressive combination therapy provides excellent prevention of T-cell-mediated rejection following renal transplantation; however, antibody-mediated rejection remains of high concern and accounts for a large number of long-term allograft losses. The recent development of protocol biopsies resulted in the definition of subclinical rejection (SCR), showing histologic evidence for rejection but unremarkable clinical course.

AREAS COVERED

This review describes the current knowledge and evidence of pharmacotherapy to treat kidney allograft rejections and covers SCR treatment options. Each substance is analyzed with regard to its classical indication and further discussed for the treatment of other forms of rejection.

EXPERT OPINION

Despite a lack of randomized trials, early acute T-cell-mediated rejection can be treated effectively in most cases without graft loss. The necessity to treat SCR is currently unclear. Due to a lack of effective therapies, new treatment approaches for antibody-mediated rejection are an urgent medical need to improve long-term outcomes. Future research should aim to better define pathophysiology and histology, stratify risk, and develop rational treatment strategies from randomized controlled trials, in order to establish the value of novel therapies in the arsenal of rejection pharmacotherapy. However, the effective prevention of rejection with minimal side effects still remains the goal in immunosuppression.

Effects of immunosuppression with tacrolimus and mycophenolate mofetil on renal histology and function in single kidney rats submitted to ischemia and reperfusion

PURPOSE

To evaluate renal histological changes and renal function in single kidney rats submitted to renal ischemia-reperfusion and to immunosuppression with tacrolimus and mycophenolate-mofetil.

METHODS

Experimental study with 80 Wistar rats distributed into control, Sham and six other groups treated with immunosuppressive drugs. Animals undergoing surgery, right nephrectomy and left renal clamping, killed on the 14th day and analyzed for renal histology, urea and creatinine.

RESULTS

The group receiving tacrolimus at higher doses (T3) showed renal histological lesions indicative of early nephrotoxicity, and significant increase in urea and creatinine. The group M (mycophenolate-mofetil alone) and the group M2 (mycophenolate-mofetil combined with half the usual dose of tacrolimus) presented a slight rise in serum urea. The groups using mycophenolate-mofetil alone or combined with tacrolimus showed creatinine levels similar to that of the group T3.

CONCLUSIONS

Histologically, the association of injury by ischemia-reperfusion with the use of tacrolimus or mycophenolate-mofetil alone demonstrated a higher rate of renal changes typical of early nephrotoxicity. In laboratory, the combination of injury by ischemia-reperfusion with tacrolimus at higher doses proved to be nephrotoxic.

Interactive effects of CYP3A4, CYP3A5, MDR1 and NR1I2 polymorphisms on tracrolimus trough concentrations in early postrenal transplant recipients

Aims: To evaluate the influences of CYP3A4, CYP3A5, MDR1 and NR1I2 polymorphisms on tacrolimus concentration in early postrenal transplant recipients. Patients & methods: A total of 159 patients were included, dose-adjusted tacrolimus trough concentration on day 7 after transplantation (C0D7/D) was calculated and 10 SNPs in four genes were genotyped. Results: CYP3A5*3 explained 32.8% of variability of tacrolimus C0D7/D. CYP3A4*1G, MDR1 1236–2677–3435 diplotype and NR1I2 -25385C > T explained 21.4% of variability of tacrolimus C0D7/D in CYP3A5 nonexpressers. Conclusion: CYP3A5*3 was the predominant determinant affecting tacrolimus concentration. Genotyping of CYP3A4/MDR1/NR1I2 polymorphisms may be helpful for better guiding tacrolimus dosing in CYP3A5 nonexpressers.

Genetic polymorphisms of pharmacogenomic VIP variants in the Uygur population from northwestern China

BACKGROUND

Drug response variability observed amongst patients is caused by the interaction of both genetic and non-genetic factors, and frequencies of functional genetic variants are known to vary amongst populations. Pharmacogenomic research has the potential to help with individualized treatments. We have not found any pharmacogenomics information regarding Uygur ethnic group in northwest China. In the present study, we genotyped 85 very important pharmacogenetic (VIP) variants (selected from the PharmGKB database) in the Uygur population and compared our data with other eleven populations from the HapMap data set.

RESULTS

Through statistical analysis, we found that CYP3A5 rs776746, VKORC1 rs9934438, and VKORC1 rs7294 were most different in Uygur compared with most of the eleven populations from the HapMap data set. Compared with East Asia populations, allele A of rs776746 is less frequent and allele A of rs7294 is more frequent in the Uygur population. The analysis of F-statistics (Fst) and population structure shows that the genetic background of Uygur is relatively close to that of MEX.

CONCLUSIONS

Our results show significant differences amongst Chinese populations that will help clinicians triage patients for better individualized treatments.

African-American race modifies the influence of tacrolimus concentrations on acute rejection and toxicity in kidney transplant recipients

STUDY OBJECTIVE

To determine the effect of tacrolimus trough concentrations on clinical outcomes in kidney transplantation, while assessing if African-American (AA) race modifies these associations.

DESIGN

Retrospective longitudinal cohort study of solitary adult kidney transplants.

SETTING

Large tertiary care transplant center.

PATIENTS

Adult solitary kidney transplant recipients (n=1078) who were AA (n=567) or non-AA (n=511).

EXPOSURE

Mean and regressed slope of tacrolimus trough concentrations. Subtherapeutic concentrations were lower than 8 ng/ml.

MEASUREMENTS AND MAIN RESULTS

AA patients were 1.7 times less likely than non-AA patients to achieve therapeutic tacrolimus concentrations (8 ng/ml or higher) during the first year after kidney transplant (35% vs 21%, respectively, p<0.001). AAs not achieving therapeutic concentrations were 2.4 times more likely to have acute cellular rejection (ACR) as compared with AAs achieving therapeutic concentrations (20.8% vs 8.5%, respectively, p<0.01) and 2.5 times more likely to have antibody-mediated rejection (AMR; 8.9% vs 3.6%, respectively, p<0.01). Rates of ACR (8.3% vs 6.7%) and AMR (2.0% vs 0.9% p=0.131) were similar in non-AAs compared across tacrolimus concentration groups. Multivariate modeling confirmed these findings and demonstrated that AAs with low tacrolimus exposure experienced a mild protective effect for the development of interstitial fibrosis/tubular atrophy (IF/TA; hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.47-1.32) with the opposite demonstrated in non-AAs (HR 2.2, 95% CI 0.90-5.1).

CONCLUSION

In contradistinction to non-AAs, AAs who achieve therapeutic tacrolimus concentrations have substantially lower acute rejection rates but are at risk of developing IF/TA. These findings may reflect modifiable time-dependent racial differences in the concentration-effect relationship of tacrolimus. Achievement of therapeutic tacrolimus trough concentrations, potentially through genotyping and more aggressive dosing and monitoring, is essential to minimize the risk of acute rejection in AA kidney transplant recipients.

Dose increase needed in most cystic fibrosis lung transplantation patients when changing from twice- to once-daily tacrolimus oral administration

AIM

The aim of this pharmacokinetic (PK) study was to evaluate tacrolimus (TAC) exposure in stable cystic fibrosis (CF) lung transplant (LT) recipients, converted from TAC twice daily to TAC once daily in an open-label, prospective, single-centre study.

METHODS

Eligible patients were post-transplant CF patients (18-65 years) with stable lung function, on stable doses of TAC twice daily and who were candidates to switch to TAC once daily. Twelve consecutive patients were included in the study. Patients had their first PK analysis on day 1, still under the stable TAC twice-daily regimen, and were converted to TAC once daily from day 2 onwards. The doses were adjusted according to clinical judgement to achieve target levels, and a second 24-h PK period profile was obtained once the patient was on a stable dosage on the therapeutic range.

RESULTS

The mean total (SD) daily dose of TAC twice daily at baseline upon enrolment was 0.17 (0.10) mg/kg/day. The mean (SD) daily dose of TAC once daily after adjustments was 0.22 (0.12) mg/kg/day. In order to achieve target C min levels with a similar AUC0-24, 82% of subjects who were converted to TAC once daily required an increase of dose, in a range of 0-66.7%, with a mean dose increase of 28%.

CONCLUSIONS

Our study results indicate that the switch for conversion from TAC twice daily to TAC once daily in patients with CF may need dose adjustment in order to reach levels within the therapeutic target.

Choosing the right dose of tacrolimus

Choosing the right dose of tacrolimus 'adapted to each individual patient' is a central question after transplantation. The pharmacokinetic behaviour of tacrolimus in paediatric patients is significantly influenced by clinical factors growth and maturation, as well as genetic factors. Large interindividual variability and narrow therapeutic index make dosage individualisation mandatory in children. CYP3A5 expressers require a 1.8-fold higher tacrolimus dose than non-expressers. A visual patient-tailored dosing chart, taking into consideration the child's weight, recent haematocrit level and CYP3A5 genotype, was developed based on a population pharmacokinetic-pharmacogenetic model, and can be used routinely to individualise tacrolimus starting dose. Area under the concentration-time curve-based dosage adaptation through limited sampling strategy and Bayesian estimation is more reliable than trough concentration. Therapeutic drug monitoring and dosage adaptation can be included in routine post-transplantation consultation and should be considered in the urgent situations (eg, rejection, adverse event, lack of compliance, change of coadministration drug with potential drug-drug interaction and other situations).

Relationship of CYP3A5 genotype and ABCB1 diplotype to tacrolimus disposition in Brazilian kidney transplant patients

AIMS

Tacrolimus (TAC) is one of the most successful immunosuppressive drugs in transplantation. Its pharmacokinetics (PK) and pharmacogenetics (PG) have been extensively studied, with many studies showing the influence of CYP3A5 on TAC metabolism and bioavailability. However, data concerning the functional significance of ABCB1 polymorphisms are uncertain due to inconsistent results. We evaluated the association between ABCB1 diplotypes, CYP3A5 polymorphisms and TAC disposition in a cohort of Brazilian transplant recipients.

METHODS

Individuals were genotyped for the CYP3A5*3 allele and ABCB1 polymorphisms (2677G>A/T, 1236C>T, 3435C/T) using a TaqMan® PCR technique. Diplotypes were analyzed for correlation with the TAC dose-normalized ratio (Co : dose).

RESULTS

We genotyped 108 Brazilian kidney recipients for CYP3A5 (11% CYP3A5*1/*1; 31% CYP3A5*1/*3 and 58% CYP3A5*3/*3) and ABCB1 haplotypes (42% CGC/CGC; 41% GCG/TTT and 17% TTT/TTT). Homozygous subjects for the CYP3A5*3 allele or carriers of the ABCB1 TTT/TTT diplotype showed a higher Co : dose ratio compared with wild type subjects [median (interquartile range) 130.2 (97.5-175.4) vs. 71.3 (45.6-109.0), P < 0.0001 and 151.8 (112.1-205.6) vs. 109.6 (58.1-132.9), P = 0.01, respectively]. When stratified for the CYP3A5*3 group, ABCB1 TTT/TTT individuals showed a higher Co : dose ratio compared with non-TTT/TTT individuals [167.8 (130.4-218.0) vs. 119.4 (100.2-166.3), P = 0.04]. Multivariate linear regression analysis showed that the effects of CYP3A5 polymorphisms and ABCB1 diplotypes remained significant after correction for confounding factors.

CONCLUSIONS

CYP3A5 is the major enzyme responsible for the marked interindividual variability in TAC PK, but it cannot be considered alone when predicting dose adjustment because ABCB1 diplotypes also affect TAC disposition, showing independent and additive effects on the TAC dose-normalized concentration.

Tacrolimus therapeutic drug monitoring and pediatric renal transplant graft outcomes

Predose monitoring of tacrolimus levels is standard practice in the care of pediatric renal transplant patients. This is despite a paucity of data investigating the ideal target range in children, and controversy as to whether tacrolimus levels correlate with renal transplant outcomes. We performed a retrospective cohort analysis of 48 renal transplant patients at a single Canadian pediatric transplant center following the initiation of a tacrolimus-mycophenolate-prednisone-based IS protocol. We analyzed the relationship of graft function, as defined by GFR up to five yr post-transplant, to the preceding mean tacrolimus level. There was no significant correlation between absolute GFR and mean tacrolimus levels (r = 0.206, p = 0.38). However, a higher mean tacrolimus level, particularly ≥10 ng/mL in the first three months after transplantation, was associated with a slower rate of decline in GFR with time (r = 0.608, p = 0.004) and with a less likelihood of developing CKD five yr after transplant. We suggest that the optimal target range for tacrolimus levels may be at the upper end of what is currently practiced and that further research to validate these findings would be useful.

The impact of APOL1, CAV1, and ABCB1 gene variants on outcomes in kidney transplantation: donor and recipient effects

Dramatic improvements have been seen in short-term kidney allograft survival over recent decades with introduction of more potent immunosuppressant medications and regimens. Unfortunately, improvements in long-term graft survival have lagged behind. The genomics revolution is providing new insights regarding the potential impact of kidney donor genotypes on long-term graft survival. Variation in the donor apolipoprotein L1 (APOL1), caveolin 1 (CAV1), and multi-drug resistance 1 encoding P-glycoprotein genes (ABCB1) are all associated with graft survival after kidney transplantation. Although the precise mechanisms whereby these donor gene variants confer risk for graft loss have yet to be determined, these findings provide novel opportunities for modifying interactive environmental factors and optimizing kidney allocation with the ultimate goal of improving long-term graft survival rates.

De novo Prograf versus de novo Advagraf: are trough level profile curves similar?

BACKGROUND

According to the clinical trials, Advagraf (ADV) has efficacy and safety profile similar to Prograf (PROG). The aim of this study was to compare the graft functions, dosages, and tacrolimus (TAC) trough level profile curves of patients on de novo PROG and ADV therapy.

METHODS

The ADV group included 39 de novo renal cases who had received initial immunosuppression (IS) with once-daily TAC (1 × 0.2 mg/kg from day1 after transplantation). We compared them with a PROG group of 38 transplant patients who received equivalent IS with twice-daily TAC (2 × 0.1 mg/kg from day1). In both groups, the IS was combined with antimetabolites and steroids. The mean follow-up time was similar (13.5 ± 7 days) in both groups after renal transplantation until the emission of the patients from our clinic.

RESULTS

TAC mean total daily dose was reduced and whole-blood trough levels decreased over the time in early postoperative days. Only on day 3 and day 4 after transplant, a significant higher adjustment in the ADV dosage was necessary to achieve sufficient TAC trough levels. The average TAC trough level profile curves were similar in PROG and ADV groups, but the individual curves were very different. Mainly in patients on ADV therapy, the initial concentrations were often >30 ng/mL, and in some cases on the 9th posttransplant day decreased to <5 ng/mL, then slowly increased into the required therapeutic range.

CONCLUSIONS

The results demonstrate that patients after renal transplantation can be safely treated de novo with ADV. Setting the required therapeutic TAC blood levels may require more attention to avoid the "fluctuations" of trough level profile curve during the early postoperative period. Our data suggest that dose adjustment of ADV can be carried out more carefully compared with PROG on the basis of clinical symptoms and the value of TAC blood levels to avoid acute rejection and toxicity.

Tacrolimus-related adverse effects in liver transplant recipients: its association with trough concentrations

BACKGROUND

Tacrolimus is an important immunosuppressant administered to patients following liver transplantation (LT), with a recommended trough concentration of 8 to 11 ng/mL to prevent allograft rejection. We retrospectively examined our data to identify the tacrolimus trough concentration that combined efficacy with minimal adverse effects.

METHODS

The case records of LT recipients, who were nondiabetic, nonhypertensive, and with normal renal parameters prior to LT were retrospectively examined for acute cellular rejection (ACR) episodes and three major adverse effects of tacrolimus, i.e. neurotoxicity, nephrotoxicity, and new onset diabetes mellitus (NODM).

RESULTS

Thirty-two LT recipients fulfilled the criteria for the study. The mean (±SD) tacrolimus level for the 290 troughs (after 10 days) was 8.5 ± 3.8 ng/mL. At 10 days, 1 month, 3 months, and 6 months, the trough values were 7.3 ± 2.9, 9.7 ± 3.4, 7.9 ± 3.3, and 7.6 ± 2.6 ng/mL, respectively. The mean time taken for stabilization of the blood pressure and biochemical parameters was 7 ± 2 days. Overall, a trough window with the least adverse effect was 7 to 7.9 ng/mL. Neurotoxicity was least in the trough range 5 to <8 ng/mL. Symptoms included headache in four, tremors in three, seizure in one, confusion and psychosis in two, and combination in three. Nephrotoxicity was least in trough 8 to <11 ng/mL. One patient progressed to chronic kidney disease at 6 months. NODM was present in 11 % to 18 % across the various trough range, including the extremes (mean trough level, 8.4 ± 4.4 ng/dL). At 6 months, five recipients were on treatment for NODM. Three recipients developed ACR, two within the first month and one at 7 weeks. The trough levels were 8.5, 9, 15.2 ng/mL, respectively. All recovered with three pulse doses of methylprednisolone.

CONCLUSION

Tacrolimus concentration of 5 to <8 ng/mL was associated with least overall toxicity, neurotoxicity, and ACR.

Clinical experience with once-daily tacrolimus in de novo kidney transplant recipients from living donors in Japan: 1-year follow up

Introduction

We assessed our clinical experience with de novo kidney transplant recipients from living donors who received once–daily tacrolimus (OD TAC). In addition, we investigated tacrolimus pharmacokinetics and compared the dose of tacrolimus in de novo kidney transplant patients treated with OD TAC or twice–daily tacrolimus (BD TAC).

Material and methods

Ten patients (3 ABO incompatible, 2 preemptive), who had received a living donor kidney transplant at our hospital since February, 2009, received OD TAC with mycophenolate mofetil, methylprednisolone, and basiliximab. OD TAC doses were adjusted to maintain tacrolimus trough levels in the range of 9–12 ng/mL. We assessed clinical and pharmacokinetic profiles. We compared average total daily dose of tacrolimus between the OD TAC and BD TAC groups.

Results

Patient survival and graft survival rates were 100% at 15.7 months. Acute rejection was not found clinically. The protocol biopsies (week 3 and month 3) did not reveal biopsy–proven acute rejection, either. No calcineurin inhibitor toxicity occurred. Doses in the OD TAC and BD TAC groups at week 3 posttransplant were 0.308 mg/kg/day and 0.149 mg/kg/day, respectively.

Conclusions

OD TAC appears to have efficacy and safety equivalent to that of BD TAC. However, a larger dose of OD TAC compared to that of BD TAC may be required during the early period after kidney transplantation.

Topical tacrolimus therapy for antibiotic-refractory pouchitis

BACKGROUND

Pouchitis is the most common complication after restorative proctocolectomy for ulcerative colitis, and it leads to pouch failure. The administration of oral antibiotics is the main treatment for pouchitis; however, in some cases, antibiotic-refractory pouchitis may develop, which requires further medical therapy.

OBJECTIVE

We investigated the applicability of topical tacrolimus for refractory pouchitis.

DESIGN

We performed a prospective pilot study. The study protocols were registered with the University Hospital Medical Information Network Clinical Trials Registry, 000006658.

SETTING

This study was conducted in the Surgical Department of Hyogo College of Medicine.

PATIENTS

Patients with antibiotic-refractory pouchitis were treated for 8 weeks with a tacrolimus enema.

MAIN OUTCOME MEASURES

The efficacy was assessed by comparing Pouchitis Disease Activity Index scores. Safety was assessed by measuring whole blood tacrolimus trough levels.

RESULTS

Ten patients with refractory pouchitis were enrolled. No severe adverse events occurred. The mean scores decreased from 15.9 ± 0.8 to 7.8 ± 0.8 during 8 weeks of treatment (p < 0.01). Specifically, the clinical symptom, endoscopic finding, and histological finding subscores decreased to 0.8 ± 0.6, 3.9 ± 0.2, and 2.9 ± 0.4. Nine patients recovered from their clinical symptoms, and 3 patients recovered from pouchitis.

LIMITATIONS

This small study was neither blinded nor randomized.

CONCLUSIONS

This study demonstrates that the use of topical tacrolimus for the treatment of refractory pouchitis is safe and effective in the short term for clinical symptoms. Although complete endoscopic healing was not achieved, this treatment may have early rescue efficacy in the treatment of antibiotic-refractory pouchitis.

Tacrolimus trough levels after month 3 as a predictor of acute rejection following kidney transplantation: a lesson learned from DeKAF Genomics

Most calcineurin inhibitor (CNI)-based protocols reduce blood trough goals approximately 2-3 months post-transplant in clinically stable kidney transplant recipients. The CNI target trough level to prevent rejection, after reduction, is unknown. Using a multivariate Cox proportional hazards model, we determined the association of time-varying tacrolimus (TAC) trough levels with acute rejection (AR) occurring in the first 6 months post-transplant, but specifically we assessed this association after 3 months. A total of 1930 patients received TAC-based immunosuppression prior to AR in a prospective study. Of the 151 (7.8%) who developed AR, 47 developed AR after 3 months post-transplant. In an adjusted time-varying multivariate model, each 1 ng/ml decrease in TAC trough levels was associated with a 7.2% increased risk of AR [hazards ratio (HR) = 1.07, 95% confidence interval (CI) (1.01, 1.14) P = 0.03] in the first 6 months. There was an additional 23% increased risk of AR with each 1 ng/ml decrease in the TAC trough levels in months 3-6 [HR = 1.23, 95% CI (1.06, 1.43) P = 0.008]. In conclusion, lower TAC trough levels were significantly associated with increased risk of AR in the first 6 months post-transplant with additional risk of AR between months 3 and 6 post-transplant. The timing and practice of TAC dose reduction should be personalized based on the individual's risk factors.

Effect of prolonged tacrolimus treatment in idiopathic membranous nephropathy with nephrotic syndrome

OBJECTIVE

Tacrolimus has been used for idiopathic membranous nephropathy (IMN) therapy, but most patients who achieved remission showed a high relapse rate when tacrolimus was withdrawn after 6-12 months of therapy. We proposed that a prolonged therapeutic course should help reduce the relapse rate.

METHODS

A total of 42 patients with nephrotic syndrome caused by IMN were randomly divided into short-term (n = 20) and long-term (n = 22) groups. All patients received initial treatment with tacrolimus and prednisone for 6 months, and afterward only the long-term patient group was tapered with low-dose tacrolimus until 24 months.

RESULTS

Over 85% of the patients achieved proteinuria reduction, serum albumin improvement and serum lipid recovery; the probability of remission in both groups was over 80% at 6 months. The remission rate was steady at over 80% after 12 and 24 months in the long-term group, but only 50 and 45%, respectively, in the short-term group. Nine patients (45%) relapsed in the short-term group after tacrolimus withdrawal, while not a single patient suffered recurrence in the long-term group. The concentration of tacrolimus remained similar between the two groups at 5-8 ng/ml during the initial 6 months, and was significantly decreased at 12 months compared to 6 months (p < 0.05), along with reduction of oral administration in the long-term group.

CONCLUSION

Combined therapy of tacrolimus with prednisone can relieve IMN significantly; prolonged tacrolimus treatment at a low blood concentration can alleviate the illness persistently, with a low recurrence rate and gratifying safety.

Tacrolimus predose concentrations do not predict the risk of acute rejection after renal transplantation: a pooled analysis from three randomized-controlled clinical trials(†)

Therapeutic drug monitoring (TDM) for tacrolimus (Tac) is universally applied. However, the concentration-effect relationship for Tac is poorly defined. This study investigated whether Tac concentrations are associated with acute rejection in kidney transplant recipients. Data from three large trials were pooled. We used univariate and multivariate analysis to investigate the relationship between biopsy-proven acute rejection (BPAR) and Tac predose concentration at five time points (day 3, 10 and 14, and month 1 and 6 after transplantation). A total of 136/1304 patients experienced BPAR, giving an overall incidence of 10.4%. We did not find any significant correlations between Tac predose concentrations and the incidence of BPAR at the different time points. In the multivariate analysis, only delayed graft function (DGF) and the use of induction therapy were independently correlated with BPAR, with an odds ratio of 2.7 [95% CI: 1.8-4.0; p < 0.001] for DGF and 0.66 [95% CI: 0.44-0.99; p = 0.049] for induction therapy. The other variables, including the Tac predose concentrations, were not statistically significantly associated with BPAR. We did not find an association between the Tac predose concentrations measured at five time points after kidney transplantation and the incidence of acute rejection occurring thereafter. Based on this study it is not possible to define the optimal target concentrations for Tac.

Validation of tacrolimus equation to predict troughs using genetic and clinical factors

AIM

Tacrolimus is an immunosuppressant used in transplantation. This article reports the validation of the authors' recently developed genetics-based tacrolimus equation that predicts troughs.

METHODS

Validation was performed in an independent cohort of 795 kidney transplant recipients receiving tacrolimus. The performance of the equation to predict initial troughs was assessed by calculating the bias and precision of the equation. For all troughs in the first 6 months post-transplant, a comparison was made between the troughs predicted using the equation versus those predicted using a basic apparent clearance model with no covariates.

RESULTS

For initial troughs, the equation had a low bias (0.2 ng/ml) and high precision (1.8 ng/ml). For all troughs, the equation predicted troughs significantly better than the basic apparent clearance model.

CONCLUSION

The tacrolimus equation had good bias and precision in predicting initial troughs and performed better than a basic apparent clearance model for all the troughs.

Tacrolimus in transplant rejection

INTRODUCTION

Renal transplantation is the best therapy for patients with end-stage renal disease. To avoid graft rejection, adequate immunosuppressive therapy is crucial. Tacrolimus is approved for prophylaxis of transplant rejection in liver, kidney or heart allograft recipients and for the treatment of allograft rejection resistant to treatment with other immunosuppressive medicinal products.

AREAS COVERED

The objective of this review is to summarize the clinical efficacy of tacrolimus in renal transplantation with special emphasis on acute rejection, refractory rejection and nephrotoxicity and post-transplant diabetes mellitus as typical adverse effects of the drug.

EXPERT OPINION

Since its approval in 1994, tacrolimus has proven its efficacy as a cornerstone of modern immunosuppressive therapy not only in numerous randomized clinical trials but also in standard clinical care. Compared with cyclosporine, the use of tacrolimus in renal transplant recipients is associated with a reduced risk for acute rejection, a reduction in the occurrence of steroid-resistant rejection and a better graft function. The avoidance of nephrotoxicity and especially post-transplant diabetes mellitus are of major interest in long-term care of renal transplant recipients.

Genetic and clinical determinants of early, acute calcineurin inhibitor-related nephrotoxicity: results from a kidney transplant consortium

BACKGROUND

Calcineurin inhibitor (CNI)-related acute nephrotoxicity is a common complication of transplantation. Clinical factors and elevated CNI levels are associated with nephrotoxicity; however, they do not fully explain the risk. Genetic factors may also predispose individuals to nephrotoxicity.

METHODS

We enrolled 945 kidney recipients into a multicenter, prospective study. DNA was genotyped for 2724 single-nucleotide polymorphisms (SNPs) using a customized chip. Cox models, unadjusted and adjusted for clinical factors, examined the association between SNPs and time to early CNI-related acute nephrotoxicity in the first 6 months posttransplant.

RESULTS

Cyclosporine was associated with a 1.49 hazard (95% confidence interval, 1.04-2.14) of acute nephrotoxicity relative to tacrolimus. Acute nephrotoxicity occurred in 22.6% of cyclosporine and 19.8% of tacrolimus recipients. The median (interquartile range) daily dose and trough concentration at time of nephrotoxicity were 400 mg (400-500 mg) and 228 ng/mL (190-272 ng/mL) in the cyclosporine group, and 6 mg (4-8 mg) and 12.6 ng/mL (10.2-15.9 ng/mL) in the tacrolimus group, respectively. In single-SNP adjusted analysis, nine SNPs in the XPC, CYP2C9, PAX4, MTRR, and GAN genes were associated with cyclosporine nephrotoxicity. In a multi-SNP analysis, SNPs from the same genes remained significant after adjusting for the clinical factors, showing that the SNPs are jointly and independently predictive of cyclosporine nephrotoxicity. No SNPs were associated with tacrolimus nephrotoxicity.

CONCLUSION

We identified SNPs that were potentially associated with early, acute cyclosporine-related nephrotoxicity. Identifying risk SNPs before transplantation provides an opportunity for personalization of immunosuppression by identifying those who may benefit from CNI-avoidance or minimization, or assist in selecting CNI type. These SNPs require independent validation.

Identification of factors affecting tacrolimus level and 5-year clinical outcome in kidney transplant patients

The purpose of this study was to identify and characterize the association of various clinical variables and CYP3A5 genotypes with the pharmacokinetics of tacrolimus and outcome over 1-5 years in kidney transplantation patients in Korea. A total of 129 recipients (aged 18-65 years) administered tacrolimus were genotyped for CYP3A5 (6986A>G in intron 3; rs776746). Clinical covariates and trough levels, doses and dose-adjusted trough levels of tacrolimus, as well as complications during the 1-5 years after transplantation, were analysed. A linear mixed model was used to investigate potential factors affecting the trough levels, doses and dose-adjusted levels of tacrolimus. We identified factors affecting chronic allograft nephropathy (CAN) and tacrolimus-related complications. After adjusting for sex, body-weight and doses of corticosteroids and mycophenolate mofetil, we noted that CYP3A5 genotypes had the most profound effect on the dose and dose-adjusted trough levels of tacrolimus 1-5 years after transplantation (p < 0.001). Trough levels of tacrolimus were associated with post-transplantation hyperlipidaemia (p < 0.05), and estimated glomerular filtration rate was associated with CAN (p < 0.05). Therefore, the CYP3A5 genotype is a variable marker for tacrolimus dose requirement, and the trough level of tacrolimus should be controlled to minimize post-transplant hyperlipidaemia to achieve optimum outcome.

Dosing equation for tacrolimus using genetic variants and clinical factors

AIM

To develop a dosing equation for tacrolimus, using genetic and clinical factors from a large cohort of kidney transplant recipients. Clinical factors and six genetic variants were screened for importance towards tacrolimus clearance (CL/F).

METHODS

Clinical data, tacrolimus troughs and corresponding doses were collected from 681 kidney transplant recipients in a multicentre observational study in the USA and Canada for the first 6 months post transplant. The patients were genotyped for 2,724 single nucleotide polymorphisms using a customized Affymetrix SNP chip. Clinical factors and the most important SNPs (rs776746, rs12114000, rs3734354, rs4926, rs3135506 and rs2608555) were analysed for their influence on tacrolimus CL/F.

RESULTS

The CYP3A5*1 genotype, days post transplant, age, transplant at a steroid sparing centre and calcium channel blocker (CCB) use significantly influenced tacrolimus CL/F. The final model describing CL/F (l h(-1)) was: 38.4 ×[(0.86, if days 6-10) or (0.71, if days 11-180)]×[(1.69, if CYP3A5*1/*3 genotype) or (2.00, if CYP3A5*1/*1 genotype)]× (0.70, if receiving a transplant at a steroid sparing centre) × ([age in years/50](-0.4)) × (0.94, if CCB is present). The dose to achieve the desired trough is then prospectively determined using the individuals CL/F estimate.

CONCLUSIONS

The CYP3A5*1 genotype and four clinical factors were important for tacrolimus CL/F. An individualized dose is easily determined from the predicted CL/F. This study is important towards individualization of dosing in the clinical setting and may increase the number of patients achieving the target concentration. This equation requires validation in an independent cohort of kidney transplant recipients.

Clinical and genetic factors affecting tacrolimus trough levels and drug-related outcomes in Korean kidney transplant recipients

PURPOSE

The purpose of this study was to characterize the effects of clinical and genetic variables on the pharmacokinetics and complications of tacrolimus during the first year after kidney transplantation.

METHODS

One hundred and thirty-two Korean kidney recipients who received tacrolimus were genotyped for ABCB1 (exons 12, 21, and 26) and CYP3A5 (intron 3). Tacrolimus trough levels, dose, or dose-adjusted trough levels and complications were compared among patients during the early stage (3, 7, 14, 30, and 90 days) and up to 1 year according to the genotypes.

RESULTS

A donor source-adjusted linear mixed model with multilevel analysis adjusting for age, body weight, hematocrit, and serum creatinine showed that CYP3A5 genotype is associated with dose-adjusted level of tacrolimus (p < 0.001). The influence of ABCB1 polymorphisms on the pharmacokinetics or complications of tacrolimus was less certain in our study. The incidence of acute rejections was significantly higher in recipients of cadaveric donor kidney (p < 0.05).

CONCLUSIONS

A generalized estimating equation model analysis showed that alopecia and hyperlipidemia were associated with dose-adjusted level of tacrolimus (p < 0.001). Genotype of CYP3A5 variants along with significant clinical covariates may be useful in individualizing tacrolimus therapy in kidney transplantation patients.

Population pharmacokinetic model and Bayesian estimator for two tacrolimus formulations--twice daily Prograf and once daily Advagraf

AIM

To investigate the differences in the pharmacokinetics of Prograf and the prolonged release formulation Advagraf and to develop a Bayesian estimator to estimate tacrolimus inter-dose area under the curve (AUC) in renal transplant patients receiving either Prograf or Advagraf.

METHODS

Tacrolimus concentration-time profiles were collected, in adult renal transplant recipients, at weeks 1 and 2, and at months 1, 3 and 6 post-transplantation from 32 Prograf treated patients, and one profile was collected from 41 Advagraf patients more than 12 months post-transplantation. Population pharmacokinetic (popPK) parameters were estimated using nonmem. In a second step, the popPK model was used to develop a single Bayesian estimator for the two tacrolimus formulations.

RESULTS

A two-compartment model with Erlang absorption (n= 3) and first-order elimination best described the data. In Advagraf patients, a bimodal distribution was observed for the absorption rate constant (K(tr) ): one group with a K(tr) similar to that of Prograf treated patients and the other group with a slower absorption. A mixture model for K(tr) was tested to describe this bimodal distribution. However, the data were best described by the nonmixture model including covariates (cytochrome P450 3A5, haematocrit and drug formulation). Using this model and tacrolimus concentrations measured at 0, 1 and 3h post-dose, the Bayesian estimator could estimate tacrolimus AUC accurately (bias = 0.1%) and with good precision (8.6%).

CONCLUSIONS

The single Bayesian estimator developed yields good predictive performance for estimation of individual tacrolimus inter-dose AUC in Prograf and Advagraf treated patients and is suitable for clinical practice.

Evaluation of limited sampling methods for estimation of tacrolimus exposure in adult kidney transplant recipients

AIMS

To examine the predictive performance of limited sampling methods for estimation of tacrolimus exposure in adult kidney transplant recipients.

METHODS

Twenty full tacrolimus area under the concentration-time curve from 0 to 12 h post-dose (AUC(0-12)) profiles (AUCf) were collected from 20 subjects. Predicted tacrolimus AUC(0-12) (AUCp) was calculated using the following: (i) 42 multiple regression-derived limited sampling strategies (LSSs); (ii) five population pharmacokinetic (PK) models in the Bayesian forecasting program TCIWorks; and (iii) a Web-based consultancy service. Correlations (r(2)) between C(0) and AUCf and between AUCp and AUCf were examined. Median percentage prediction error (MPPE) and median absolute percentage prediction error (MAPE) were calculated.

RESULTS

Correlation between C(0) and AUCf was 0.53. Using the 42 LSS equations, correlation between AUCp and AUCf ranged from 0.54 to 0.99. The MPPE and MAPE were <15% for 29 of 42 equations (62%), including five of eight equations based on sampling taken ≤2 h post-dose. Using the PK models in TCIWorks, AUCp derived from only C(0) values showed poor correlation with AUCf (r(2)=0.27-0.54) and unacceptable imprecision (MAPE 17.5-31.6%). In most cases, correlation, bias and imprecision estimates progressively improved with inclusion of a greater number of concentration time points. When concentration measurements at 0, 1, 2 and 4 h post-dose were applied, correlation between AUCp and AUCf ranged from 0.75 to 0.93, and MPPE and MAPE were <15% for all models examined. Using the Web-based consultancy service, correlation between AUCp and AUCf was 0.74, and MPPE and MAPE were 6.6 and 9.6%, respectively.

CONCLUSIONS

Limited sampling methods better predict tacrolimus exposure compared with C(0) measurement. Several LSSs based on sampling taken 2 h or less post-dose predicted exposure with acceptable bias and imprecision. Generally, Bayesian forecasting methods required inclusion of a concentration measurement from >2 h post-dose to adequately predict exposure.

Evaluation of tacrolimus abbreviated area-under-the-curve monitoring in renal transplant patients who are potentially at risk for adverse events

In a cohort of 32 renal transplant patients who are potentially at risk for adverse events, we compared tacrolimus (TAC) abbreviated AUC values calculated by a method developed in Asians (AUCw) with those derived for Caucasians (AUCa). The relationships between TAC trough (C0), abbreviated AUC, and biopsy results were also assessed. Forty-eight AUCs and 15 associated biopsies were evaluated. For AUCs obtained only from Caucasian patients, median AUCw value was lower than that of AUCa (104 vs. 115 ng×h/mL, n=29, p<0.0001). AUCs obtained from the two methods for all patients correlated with C0 (rs>0.72, n=48, p<0.0001). Median AUCw (72.9 vs. 174 ng×h/mL, p=0.043) and AUCa (81.0 vs. 203 ng×h/mL, p=0.043) were lower in patients experiencing biopsy-proven acute rejection (AR) than those with normal histology. C0 tended to be lower in biopsies showing AR>6 months post-transplant (5.80 vs. 11.0 ng/mL, p=0.110). Thus, lower abbreviated AUCs were obtained for Caucasians using a method developed in Asians. C0 correlated well with abbreviated AUCs. Lower C0 and AUC appeared to be associated with biopsy-proven AR>6 months post-transplant. Further prospective evaluation of TAC AUC and C0 monitoring in a larger cohort of patients is warranted.

Novel strategies for immune monitoring in kidney transplant recipients

The ongoing quandary in kidney transplantation is discovering methods to prolong graft survival. To achieve this, there is a search for optimal methods to use immunosuppressive therapy, where rejection and chronic graft damage is minimized without causing an increased risk of infections, malignancy, or toxicities. The purpose of this review was to discuss the limitations of current immunosuppressant drug monitoring as well as the clinical application of novel methods of monitoring both immunosuppressants and the immune reaction within the allograft.

Single center prospective study of tacrolimus efficacy and safety in the treatment of various manifestations in systemic lupus erythematosus

The aim of this study was to prospectively evaluate the efficacy and safety of tacrolimus (TAC) in various manifestations of systemic lupus erythematosus (SLE) patients in daily clinical practice. Each of the 21 TAC-treated patients with SLE in our care over 2 years was enrolled in this open-label trial. Patients were administered TAC at a dosage of 1-6 mg once daily, followed up for 24 weeks. Efficacy and safety were evaluated utilizing clinical and laboratory findings. As treatment targets, TAC was preferentially used with oral corticosteroid administration for mild active manifestations such as arthritis, skin eruptions, or asymptomatic nephritis. In efficacy, the mean value of the SLE disease activity index was significantly reduced to 4.1, 2.7, 1.8, and 1.2 (N=21, 20, 16 and 13) at 0, 4, 12, and 24 weeks, respectively. In eight cases, treatment was discontinued within 24 weeks due to insufficient effects (6 cases) and side effects (2 cases). Non-serious side effects were observed in only five cases (23.8%) over 24 weeks. TAC can be considered both effective and safe for the treatment of various manifestations of SLE.

Trough tacrolimus concentrations in the first week after kidney transplantation are related to acute rejection

There is evidence showing the importance of reaching immunosuppressant target concentrations as soon as possible. The aim of this study was to evaluate the relationship between tacrolimus trough concentrations within the first week after transplantation and the rate of acute rejection. In this descriptive-analytic study, we included 57 renal transplant patients receiving tacrolimus as the primary immunosuppressive drug. After univariate analysis, donor age, duration of hospital stay, and creatinine clearance (third month) showed significant differences between rejecters and nonrejecters. In addition, mean tacrolimus trough concentrations on day 5, day 7, mean of days 1-7, and mean of days 5-7 were found to be significantly lower in rejecters (P = 0.009, P = 0.012, P = 0.006, and P = 0.035, respectively). Receiver operating characteristic curve analysis with tacrolimus trough concentrations measured on days 5 and 7 was able to discriminate between patients with and without acute rejection (P = 0.028 and P = 0.048 after Bonferroni correction). The tacrolimus trough concentration with the best sensitivity-specificity balance was 9.3 ng/mL on day 5 and 8.7 ng/mL on day 7. In the Kaplan-Meier analysis, patients with tacrolimus trough concentrations below 9.3 mg/mL on day 5 showed a lower survival time without acute rejection (P = 0.048 after correction) in comparison with patients with tacrolimus trough concentrations above this concentration. After logistic regression, we obtained a model relating rejection with sex, donor age, and tacrolimus trough concentrations on day 5 (P = 0.004). No significant relationship between tacrolimus trough concentrations and delta creatinine clearance from week 1 to month 3 was obtained. These results confirm that tacrolimus trough concentrations during the first week are an important predictor of acute rejection. Therefore, it is critical to reach target blood concentrations of tacrolimus as soon as possible to improve allograft survival.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Opportunities to optimize tacrolimus therapy in solid organ transplantation: report of the European consensus conference

In 2007, a consortium of European experts on tacrolimus (TAC) met to discuss the most recent advances in the drug/dose optimization of TAC taking into account specific clinical situations and the analytical methods currently available and drew some recommendations and guidelines to help clinicians with the practical use of the drug. Pharmacokinetic, pharmacodynamic, and more recently pharmacogenetic approaches aid physicians to individualize long-term therapies as TAC demonstrates a high degree of both between- and within-individual variability, which may result in an increased risk of therapeutic failure if all patients are administered a uniform dose. TAC has undoubtedly benefited from therapeutic drug monitoring, but interpretation of the blood concentration is confounded by the relative differences between the assays. Single time points, limited sampling strategies, and area under concentration-time curve have all been considered to determine the most appropriate sampling procedure that correlates with efficacy. Therapeutic trough TAC concentration ranges have changed since the initial introduction of the drug, while still maintaining adequate immunosuppression and avoiding drug-related adverse effects. Pharmacodynamic markers have also been considered advantageous to the clinician, which may better reflect efficacy and safety, taking into account the between-individual variability rather than whole blood concentrations. The choice of method, differences between methods, and potential pitfalls of the method should all be considered when determining TAC concentrations. The recommendations of this consensus meeting regarding the analytical methods include the following: encourage the development and promote the use of analytical methods displaying a lower limit of quantification (1 ng/mL), perform careful validation when implementing a new analytical assay, participate in external proficiency testing programs, promote the use of certified material as calibrators in high-performance liquid chromatography with mass spectrometric detection methods, and take account of the assay and intermethod bias when comparing clinical trial outcomes. It is also important to consider that TAC concentrations may also be influenced by other factors such as specific pharmacokinetic characteristics associated with the population, drug interactions, pharmacogenetics, adverse events that may alter TAC concentrations, and any change in the oral formulation that may result in pharmacokinetic changes. This meeting emphasized the importance of obtaining multicenter prospective trials to assess the efficacy of alternative strategies to TAC trough concentrations whether it is other single time points or area under the concentration-time curve Bayesian estimation using limited sampling strategies and to select, standardize, and validate routine biomarkers of TAC pharmacodynamics.