Lower variability in 24-hour exposure during once-daily compared to twice-daily tacrolimus formulation in kidney transplantation

Why is the rectal route for NSAIDS favorable for preventing post-ERCP pancreatitis?

OBJECTIVE

Acute pancreatitis is a frequent, burdensome adverse event of endoscopic retrograde cholangiography (ERCP). Rectal nonsteroidal anti-inflammatory drugs (NSAIDs) have reduced post-ERCP pancreatitis (PEP) risk by about 50 % and show greater efficacy over parenteral or oral administration, although the mechanism for its superiority remains unclear. To probe this question, we investigated in a preclinical model, the pharmacokinetics in the blood, pancreas and other tissues of the NSAID diclofenac given via the rectal, intravenous, or intragastric routes.

METHODS

The data on diclofenac was extracted from a larger study that examined a combination of diclofenac and tacrolimus. 20.8 mg diclofenac/kg body weight, which is the mouse equivalent dosing used in clinical practice for PEP prophylaxis, was administered to C57BL/6J mice via the rectal, intravenous and intragastric (oral) routes. Cross-collection of blood and tissues was done at various timepoints after administration for the evaluation of drug levels and pharmacokinetic parameters.

RESULTS

Rectal diclofenac demonstrated favorable blood pharmacokinetics and systemic bioavailability as well as sustained pancreas penetration. The total pancreas exposure to diclofenac over 24 h following rectal dosing was not significantly different as compared to intravenous and oral dosing.

CONCLUSION

Our findings suggest that the efficacy of rectal diclofenac in PEP prevention relates more to its higher and consistent systemic exposure than its absolute pancreas levels. The implications are that the rectal route provides both systemic and pancreas exposure for the full duration of PEP vulnerability.

The tradeoff between the efficacy of calcineurin inhibitors: prevention of allograft rejection vs. post-transplant renal and cardiovascular complications

Solid organ transplantation has emerged as a crucial intervention in the field of medicine. During transplantation, our human body perceives the organ as an exogenous entity or graft, initiating an immune reaction to eliminate it. This immune response ultimately culminates in the rejection of the graft. So, to mitigate the possibility of graft rejection, implementing immune suppression is imperative. In this context, the utilization of calcineurin inhibitors (CNIs) assumes a pivotal role. Calcineurin inhibitors significantly preserve immunosuppression following solid organ transplantation. Calcineurin inhibitors have considerably improved short-term results in renal transplantation by reducing acute rejection rates. Concerning the limited therapeutic window of these medications, careful monitoring of pharmacological treatment and individual doses is required. However, a significant number of patients do experience CNI toxicity. Side effects of CNIs include renal failure, hypertension, respiratory disorders, gastrointestinal damage, gingivitis, and so on. Higher trough level of the drug causes acute nephrotoxicity, which is of three types: functional toxicity, tubular toxicity, and vascular toxicity. Acute nephrotoxicity, if untreated, leads to irreversible, progressive deterioration of allograft function, leading to chronic nephrotoxicity. Cardiovascular toxicity of CNIs includes atrial hypertension caused by vasoconstriction of the afferent arteriole, vascular remodeling, hypertrophy, dyslipidemia, and also the onset of diabetes. Such clinical complications further affect the patient's survivability and subjective well-being, possibly leading to graft loss. This review focuses on the most severe side effects of CNIs: renal and cardiovascular toxicity.

Factors and interventions affecting tacrolimus intrapatient variability: A systematic review and meta-analysis

BACKGROUNDS

Tacrolimus is a cornerstone of posttransplantation immunosuppressive regimens. Despite routine monitoring, the efficacy of its trough concentrations in reflecting drug concentration fluctuations is limited. Intrapatient variability (IPV) emerges as a novel monitoring marker for predicting clinical outcomes. However, understanding the factors affecting IPV and assessing interventions to address it remain enigmatic, posing a conundrum in clinical management.

OBJECTIVES

This systematic review aimed to investigate a spectrum of factors affecting IPV and assess the effect of strategic interventions, thereby charting a course for enhanced clinical stewardship.

METHODS

We electronically searched of PubMed, Embase, and the Cochrane Library databases for studies investigating factors and interventions affecting IPV up to October 2023. Two reviewers independently screened literature, extracted data, and assessed quality, using RevMan 5.4.1 software for meta-analysis.

RESULTS

A total of 15 randomized controlled trials (RCTs), 34 cohort studies, and 20 self-controlled studies were included. The results indicated that IPV was significantly higher in cytochrome P450 3A5 (CYP3A5) expressers, nonadherent patients, patients taking proton pump inhibitors or statins, and Black or African American recipients, whereas recipients consuming extended-release formulation exhibited lower IPV. Additionally, the participation of pharmacists had a positive effect on improving IPV.

CONCLUSIONS

Factors affecting IPV encompassed genotype, formulation, adherence, drug combinations, and ethnicity, with each factor exerting varying degrees of effect. Identifying these factors was crucial for developing targeted intervention strategies. While the participation of pharmacists held a promise in improving IPV, further investigation of interventions such as mobile technology, educational measures to enhance adherence, and personalized dosing regimens was warranted.

A Systematic Literature Review on the Use of Dried Biofluid Microsampling in Patients With Kidney Disease

BACKGROUND

Kidney disease is fairly unique due to the lack of symptoms associated with disease activity, and it is therefore dependent on biological monitoring. Dried biofluids, particularly dried capillary blood spots, are an accessible, easy-to-use technology that have seen increased utility in basic science research over the past decade. However, their use is yet to reach the kidney patient population clinically or in large-scale discovery science initiatives. The aim of this study was to systematically evaluate the existing literature surrounding the use of dried biofluids in kidney research.

METHODS

A systematic literature review was conducted using three search engines and a predefined search term strategy. Results were summarised according to the collection method, type of biofluid, application to kidney disease, cost, sample stability and patient acceptability.

RESULTS

In total, 404 studies were identified and 67 were eligible. In total, 34,739 patients were recruited to these studies with a skew towards male participants (> 73%). The majority of samples were blood, which was used either for monitoring anti-rejection immunosuppressive drug concentrations or for kidney function. Dried biofluids offered significant cost savings to the patient and healthcare service. The majority of patients preferred home microsampling when compared to conventional monitoring.

CONCLUSION

There is an unmet need in bringing dried microsampling technology to advance kidney disease despite its advantages. This technology provides an opportunity to upscale patient recruitment and longitudinal sampling, enhance vein preservation and overcome participation bias in research.

Erratic tacrolimus levels at 6 to 12 months post-lung transplant predicts poor outcomes

Background

It has previously been described that erratic tacrolimus blood levels are associated with graft failure in kidney and liver transplantation. Using a small cohort, we previously described that a higher tacrolimus standard deviation (SD) 6 to 12 months after lung transplantation increased the risk of chronic lung allograft dysfunction (CLAD) and death. We aimed to assess this in a larger cohort using the coefficient of variation (CoV) and identify potential risk factors for higher CoV.

Methods

We retrospectively reviewed 351 lung transplant recipients who received tacrolimus-based immunosuppression therapy. Cox proportional hazard modeling was used to investigate the effects of mean tacrolimus and CoV levels on survival and CLAD.

Results

Tacrolimus CoV from 6 to 12 months was independently associated with both CLAD (hazard ratio [HR], 19.99; 95% CI, 7.55-52.91; p < 0.001) and death (HR, 14.57; 95% (confidence interval) CI, 6.08-34.90; p < 0.001). Conversely, the mean trough tacrolimus blood concentration between 6 to 12 months was not associated with an increased risk of CLAD (HR, 0.94; 95% CI, 0.84-1.06; p = 0.34) or death (HR, 0.91; 95% CI, 0.82-1.01; p = 0.07). In a multivariable model, erratic tacrolimus levels were associated with antifungal use (β 0.10 95% CI 0.54-1.51, p < 0.001) and younger age (Î2 -0.0015, 95% CI -0.17 to -0.03, p = 0.005 per 5 years).

Conclusions

Erratic tacrolimus levels at 6 to 12 months post-lung transplant were associated with poor lung transplant outcomes. Future studies are required to determine whether interventions designed to optimize tacrolimus CoV could improve lung transplant outcomes.

The effect of tacrolimus conversion from immediate- to extended-release formulation on renal function in renal transplant patients: a meta-analysis

Objective: Tacrolimus formulation affects the outcomes of a renal transplant, while the effect of its immediate- to extended-release conversion remains controversial. This meta-analysis aimed to compare the renal function before and after tacrolimus immediate- to extended-release conversion in renal transplant patients. Methods: PubMed, Cochrane, Embase, CNKI, CQVIP, and Wanfang databases were searched for articles regarding the effect of tacrolimus conversion from immediate- to extended-release formulation on renal function in renal transplant patients. The data on serum creatinine (Scr) or the estimated glomerular filtration rate (eGFR) before and after conversion were extracted and analyzed. Results: Ten studies with 743 renal transplant patients were included. Scr was reduced after conversion versus before conversion [mean difference (MD) (95% confidence interval (CI)): -8.00 (-14.33; -1.66) μmol/L, p = 0.01]. However, eGFR only showed an increased trend after conversion versus before conversion (MD (95% CI): 2.21 (-1.62, 6.03) mL/min/1.73 m2, p = 0.26) but without statistical significance. Furthermore, in patients with a follow-up duration ≥48 weeks, Scr was decreased after conversion versus before conversion (p = 0.005), but eGFR remained unchanged (p = 0.68). However, in patients with a follow-up duration <48 weeks, both Scr (p = 0.36) and eGFR (p = 0.24) were not different before conversion versus after conversion. Moreover, publication bias risk was low, and robustness assessed by sensitivity analysis was generally good. Conclusion: This meta-analysis favors studies indicating that the conversion of tacrolimus from an immediate-release to an extended-release formulation could improve the kidney function to some extent in renal transplant patients, and this advancement may be related to the administration period.

Efficacy and safety of once-daily prolonged-release tacrolimus versus twice-daily tacrolimus in kidney transplant recipients: A meta-analysis and trial sequential analysis

BACKGROUND

Kidney transplantation is the most important treatment for end-stage renal disease. Immunosuppressive therapies can prevent acute rejection for kidney transplant recipients. Tacrolimus is usually administered to prevent graft rejection after transplantation. Previous studies have indicated that once-daily tacrolimus may improve medication adherence. Therefore, this meta-analysis aimed to compare clinical outcomes between once-daily and twice-daily tacrolimus in de novo renal transplant patients.

METHODS

Eligible studies were identified from the Cochrane Library Database, PubMed, and Embase until July 2022. Those randomized controlled trials (RCTs) evaluating once-daily versus twice-daily tacrolimus formulations in de novo renal transplantation were included. A summary risk ratio (RR) and standardized mean difference (SMD) with the 95% confidence interval (CI) were estimated using a random-effects model.

RESULTS

In total, nine RCTs were included. There were no differences in biopsy-confirmed acute rejection rates between patients with once-daily and those with twice-daily tacrolimus (RR, 0.91; 95% CI, 0.73-1.13) in 12 months. Regarding renal function, there was no significant difference between the once-daily and twice-daily tacrolimus groups (SMD, -0.03; 95% CI, -0.12 to 0.07). In addition, the risk of graft failure, death, and adverse events in the first year was similar for the once-daily and twice-daily tacrolimus groups.

CONCLUSION

Our major findings suggest that de novo renal transplantation recipients receiving once-daily tacrolimus immediately after transplantation have comparable efficacy and safety with those recipients who received twice-daily tacrolimus. Therefore, once-daily tacrolimus medication can be an alternative for de novo renal transplantation recipients.

Tacrolimus-why pharmacokinetics matter in the clinic

The calcineurin inhibitor (CNI) Tacrolimus (Tac) is the most prescribed immunosuppressant drug after solid organ transplantation. After renal transplantation (RTx) approximately 95% of recipients are discharged with a Tac-based immunosuppressive regime. Despite the high immunosuppressive efficacy, its adverse effects, narrow therapeutic window and high intra- and interpatient variability (IPV) in pharmacokinetics require therapeutic drug monitoring (TDM), which makes treatment with Tac a major challenge for physicians. The C/D ratio (full blood trough level normalized by daily dose) is able to classify patients receiving Tac into two major metabolism groups, which were significantly associated with the clinical outcomes of patients after renal or liver transplantation. Therefore, the C/D ratio is a simple but effective tool to identify patients at risk of an unfavorable outcome. This review highlights the challenges of Tac-based immunosuppressive therapy faced by transplant physicians in their daily routine, the underlying causes and pharmacokinetics (including genetics, interactions, and differences between available Tac formulations), and the latest data on potential solutions to optimize treatment of high-risk patients.

Tacrolimus Exposure Before and After a Switch From Twice-Daily Immediate-Release to Once-Daily Prolonged Release Tacrolimus: The ENVARSWITCH Study

LCP-tacrolimus displays enhanced oral bioavailability compared to immediate-release (IR-) tacrolimus. The ENVARSWITCH study aimed to compare tacrolimus AUC0-24 h in stable kidney (KTR) and liver transplant recipients (LTR) on IR-tacrolimus converted to LCP-tacrolimus, in order to re-evaluate the 1:0.7 dose ratio recommended in the context of a switch and the efficiency of the subsequent dose adjustment. Tacrolimus AUC0-24 h was obtained by Bayesian estimation based on three concentrations measured in dried blood spots before (V2), after the switch (V3), and after LCP-tacrolimus dose adjustment intended to reach the pre-switch AUC0-24 h (V4). AUC0-24 h estimates and distributions were compared using the bioequivalence rule for narrow therapeutic range drugs (Westlake 90% CI within 0.90-1.11). Fifty-three KTR and 48 LTR completed the study with no major deviation. AUC0-24 h bioequivalence was met in the entire population and in KTR between V2 and V4 and between V2 and V3. In LTR, the Westlake 90% CI was close to the acceptance limits between V2 and V4 (90% CI = [0.96-1.14]) and between V2 and V3 (90% CI = [0.96-1.15]). The 1:0.7 dose ratio is convenient for KTR but may be adjusted individually for LTR. The combination of DBS and Bayesian estimation for tacrolimus dose adjustment may help with reaching appropriate exposure to tacrolimus rapidly after a switch.

Efficacy of Prolonged-release Tacrolimus After Conversion From Immediate-release Tacrolimus in Kidney Transplantation: A Retrospective Analysis of Long-term Outcomes From the ADMIRAD Study

Prolonged-release tacrolimus (PRT) may offer improved outcomes after kidney transplantation compared with immediate-release tacrolimus (IRT). However, data on outcomes beyond 5-y posttransplantation are lacking.

Methods

A retrospective, noninterventional chart review study examined long-term graft survival in adult kidney transplant participants in the Adherence Measurement in Stable Renal Transplant Patients Following Conversion From Prograf to Advagraf (ADMIRAD) clinical trial at 4 Belgian sites. Patients were randomized to receive once-daily PRT or twice-daily IRT for 6 mo, followed by treatment as per real-world clinical practice. Data were collected retrospectively from randomization day until December 31, 2018. Primary endpoints included efficacy failure, defined as a composite endpoint of graft loss, biopsy-confirmed acute rejection, and graft dysfunction. Secondary endpoints included overall patient survival and course of kidney function.

Results

This analysis included 78.5% of patients from ADMIRAD (n = 108 PRT; n = 64 IRT). The Kaplan-Meier survival rate without efficacy failure from randomization to year 5 was 0.741 (95% confidence interval [CI]: 0.647, 0.813) for the PRT group (n = 80), and 0.667 (95% CI: 0.536, 0.768) for the IRT group (n = 42) and remained higher for PRT throughout 10 y follow-up (P = 0.041). The Kaplan-Meier estimate of overall survival from the time of last transplant was 0.981 (95% CI: 0.928, 0.995) and 0.880 (95% CI: 0.802, 0.928) at 5 and 10 y in the PRT group. Kidney function parameters and tacrolimus trough levels remained stable over the follow-up period.

Conclusions

Patients in the ADMIRAD study who received PRT for up to 10 y had improved long-term outcomes compared with patients receiving IRT, with a consistent effect on both graft and patient survival.

Tacrolimus Formulation, Exposure Variability, and Outcomes in Kidney Transplant Recipients

INTRODUCTION

Few studies have compared within-patient variability measures of tacrolimus trough levels by formulation and assessed within-patient variability on outcomes of kidney transplant recipients.

RESEARCH QUESTIONS

(1) To compare within-patient variability of trough levels when converting from twice-daily to once-daily tacrolimus using standard deviation, coefficient of variation, and intrapatient variability percent. (2) To use the 3 measures of variability to examine the relationship between tacrolimus once-daily within-patient variability and total graft failure (i.e., return to chronic dialysis, pre-emptive retransplant, death with graft function).

DESIGN

In this observational cohort study, within-patient variability of trough levels pre- and post-conversion from twice-daily to once-daily tacrolimus were compared using Wilcoxon matched-pairs signed-rank test. Graft outcomes were analyzed using Kaplan-Meier curves and multivariable Cox proportional hazards models.

RESULTS

In 463 patients, within-patient variability differences pre- and post-conversion of median standard deviation, coefficient of variation, and intrapatient variability percent were -0.16 (P = 0.09), -0.01 (P = 0.52), and -1.41 (P = 0.32), respectively. Post-conversion, every 1 unit increase in within-patient variability standard deviation and intrapatient variability percent and every 0.1 unit increase in the coefficient of variation was associated with an increased hazard ratio [1.19 (P = 0.004), 1.02 (P = 0.030), 1.13 (P = 0.001), respectively] of total graft failure. Post-conversion, within-patient variability above cohort medians using standard deviation and coefficient of variation had a significantly higher risk of total graft failure.

DISCUSSION

Under a program-wide conversion, no significant difference was observed in within-patient variability post-conversion from twice-daily to once-daily tacrolimus using the three measures of variability. High within-patient variability was associated with adverse transplant outcomes post-conversion.

Long-term Prolonged-release Tacrolimus-based Immunosuppression in De Novo Kidney Transplant Recipients: 5-Y Prospective Follow-up of Patients in the ADVANCE Study

Although prolonged-release tacrolimus (PR-T) is widely approved for posttransplantation immunosuppression in kidney recipients, large-scale studies are required to assess long-term outcomes. We present follow-up data from the Advagraf-based Immunosuppression Regimen Examining New Onset Diabetes Mellitus in Kidney Transplant Recipients (ADVANCE) trial, in which kidney transplant patients (KTPs) received corticosteroid minimization with PR-T.

Methods

ADVANCE was a 24-wk, randomized, open-label, phase-4 study. De novo KTPs received PR-T with basiliximab and mycophenolate mofetil and were randomized to receive an intraoperative corticosteroid bolus plus tapered corticosteroids until day 10 (arm 1) or an intraoperative corticosteroid bolus (arm 2). In this 5-y, noninterventional follow-up, patients received maintenance immunosuppression according to standard practice. The primary endpoint was graft survival (Kaplan-Meier). Secondary endpoints included patient survival, biopsy-confirmed acute rejection-free survival, and estimated glomerular filtration rate (4-variable modification of diet in renal disease).

Results

Follow-up study included 1125 patients. Overall graft survival at 1 and 5 y posttransplantation was 93.8% and 88.1%, respectively, and was similar between treatment arms. At 1 and 5 y, patient survival was 97.8% and 94.4%, respectively. Five-year graft and patient survival rates in KTPs who remained on PR-T were 91.5% and 98.2%, respectively. Cox proportional hazards analysis demonstrated similar risk of graft loss and death between treatment arms. Five-year biopsy-confirmed acute rejection-free survival was 84.1%. Mean ± standard deviation values of estimated glomerular filtration rate were 52.7 ± 19.5 and 51.1 ± 22.4 mL/min/1.73 m² at 1 and 5 y, respectively. Fifty adverse drug reactions were recorded, probably tacrolimus-related in 12 patients (1.5%).

Conclusions

Graft survival and patient survival (overall and for KTPs who remained on PR-T) were numerically high and similar between treatment arms at 5 y posttransplantation.

Tacrolimus dose adjustment is not necessary in dose to dose conversion from a twice daily to a prolonged release once daily dose form

Twice daily TAC (BID TAC) and prolonged released once daily dose tacrolimus (OD TAC) have different pharmacokinetic (PK) profiles in kidney transplant (KT) recipients. Precise dose adjustment recommendations when converting from BID TAC to OD TAC remain inconclusive. A single center, PK study was conducted in stable KT recipients taking constant doses of TAC, mycophenolic acid, and prednisolone. The area under the concentration-time curve (AUC) 0-24 and C_trough were measured before and 4 weeks after 1:1 conversion from BID TAC to OD TAC without subsequent dose adjustment. A 90% confidence interval (CI) of geometric mean ratio (GMR) of OD TAC/BID TAC within the range of 0.9-1.11 was utilized to indicate equivalence of the narrow therapeutic index drugs. The roles of CYP3A5 genotypic polymorphism on PK parameters were also assessed. There were 20 patients with median time since transplantation of 18 months. The mean of CKD-EPI eGFR was 60.7 ± 16.43 mL/min/1.73 m². The median total daily TAC dose of 0.058 mg/kg/day. The geometric means (%CV) of AUC_0-24 of OD and BID TAC were 205.16 (36.4%) and 210.3 (32.5%) ng/mL × h, respectively, with a GMR of 0.98 (90%CI 0.91-1.04). The geometric means (%CV) of C_trough of OD TAC and BID TAC were 5.43 (33.1%) and 6.09 (34.6%) ng/mL, respectively. The GMR of C_trough was 0.89 (90%CI 0.82-0.98), which was below 0.9. The newly calculated target C_trough level of OD TAC was 4.8-6.2 ng/mL. The best abbreviated AUC_0-24 was AUC = 0.97(C0) + 5.79(C6) + 18.97(C12) - 4.26. The GMR AUC_0-24 was within the range of 0.9-1.11 irrespective of CYP3A5 genotypic polymorphism while the GMR of C_trough was below 0.9 only in the CYP3A5 expressor patients. The 1:1 conversion from BID TAC to OD TAC without subsequent dose adjustment provided similar AUC_0-24 regardless of CYP3A5 genotypic polymorphism. However, the C_trough was lower in the CYP3A5 expressor group. Therefore, it is not necessary to routinely increase the OD TAC dose after conversion.Trial registration: Thai Clinical Trials Registry (TCTR20210715002).

Personalized immunosuppression after kidney transplantation

With advances in immunosuppressive therapy, there have been significant improvements in acute rejection rates and short-term allograft survival in kidney transplant recipients. However, this success has not been translated into long-term benefits by the same magnitude. Optimization of immunosuppression is important to improve the clinical outcome of transplant recipients. It is important to note that each patient has unique attributes and immunosuppression management should not be a one-size-fits-all approach. Elderly transplant patients are less likely to develop acute rejection but more likely to die from infectious and cardiovascular causes than younger patients. For those with post-transplant cancers and BK polyomavirus-associated nephropathy, reduction of immunosuppression can increase the risk of rejection. Therapeutic drug monitoring (TDM) is routinely used for dosage adjustment of several immunosuppressive drugs. It has been hoped that pharmacogenetics can be used to complement TDM in optimizing drug exposure. Among the various drug-genotype pairs being investigated, tacrolimus and CYP3A5 gives the most promising results. Different studies have consistently shown that CYP3A5 expressers require a higher tacrolimus dose and take longer time to achieve target blood tacrolimus levels than nonexpressers. However, for pharmacogenetics to be widely used clinically, further trials are necessary to demonstrate the clinical benefits of genotype-guided dosing such as reduction of rejection and drug-related toxicities. The development of different biomarkers in recent years may help to achieve true personalized therapy in transplant patients.

The Role of Intra-Patient Variability of Tacrolimus Drug Concentrations in Solid Organ Transplantation: A Focus on Liver, Heart, Lung and Pancreas

Tacrolimus, the keystone immunosuppressive drug administered after solid organ transplantation, presents a narrow therapeutic index and wide inter- and intra-patient pharmacokinetic variability (IPV). The latter has been fairly studied in kidney transplantation, where it could impact outcomes. However, literature about other transplanted organ recipients remains inconclusive. This review aimed at summarizing the evidence about the IPV of tacrolimus concentrations outside of the scope of kidney transplantation. First, factors influencing IPV will be presented. Then, the potential of IPV as a biomarker predictive of graft outcomes will be discussed in liver, heart, lung and pancreas transplantation. Lastly, strategies to reduce IPV will be reviewed, with the ultimate objective being ready-to-implement solutions in clinical practice by transplantation professionals.

Flat Pattern Peaks of Tacrolimus Absorption and Associated Pharmacogenomic Variants in Kidney Transplantation Recipients

BACKGROUND

Tacrolimus is the most commonly used immunosuppressive drug in solid organ transplantation. After administering a conventional twice-daily dose of tacrolimus, peak levels were achieved within the first 1.5 to 2 hours. A group of patients showed different early absorption phase of tacrolimus after kidney transplantation.

METHODS

Trough(C₀) and 1.5-hour blood levels (C_1.5) of tacrolimus were measured in 95 kidney transplantation recipients. Patients with a C_1.5/C₀ < 1.5 and > 1.5 were defined as those having flat pattern peaks and as controls, respectively. Transplantation outcomes were compared between the groups. Whole exome sequencing was performed to investigate the genetic susceptibility to flat pattern peaks.

RESULTS

Twenty-eight patients showed flat pattern peaks. The mean C_1.5/C₀ values were 1.13 ± 0.22 and 3.78 ± 1.25 in the flat pattern peak and control groups, respectively. In multivariate analysis, flat pattern peak was an independent risk factor for biopsy-proven acute rejection (BPAR) and/or borderline change (P = 0.014). Patients having flat pattern peaks showed significantly lower post-transplant 36-month estimated glomerular filtration rate (P = 0.001). Two single nucleotide variants in ABCB1 genes, rs1922242 and rs2235035, were associated with flat pattern peaks (P = 0.019 and P = 0.027, respectively).

CONCLUSION

Both of C_1.5 and C₀ should be measured to distinguish the patients showing unique initial absorption. A C_1.5/C₀ ratio lower than 1.5 was associated with an increased risk of BPAR and/or borderline change. Single nucleotide variants s in ABCB1 gene might influence the flat pattern peaks of tacrolimus absorption.

Impact of intrapatient blood level variability of calcineurin inhibitors on heart transplant outcomes

INTRODUCTION AND OBJECTIVES

Intrapatient blood level variability (IPV) of calcineurin inhibitors has been associated with poor outcomes in solid-organ transplant, but data for heart transplant are scarce. Our purpose was to ascertain the clinical impact of IPV in a multi-institutional cohort of heart transplant recipients.

METHODS

We retrospectively studied patients aged ≥18 years, with a first heart transplant performed between 2000 and 2014 and surviving≥ 1 year. IPV was assessed by the coefficient of variation of trough levels from posttransplant months 4 to 12. A composite of rejection or mortality/graft loss or rejection and all-cause mortality/graft loss between years 1 to 5 posttransplant were analyzed by Cox regression analysis.

RESULTS

The study group consisted of 1581 recipients (median age, 56 years; women, 21%). Cyclosporine immediate-release tacrolimus and prolonged-release tacrolimus were used in 790, 527 and 264 patients, respectively. On multivariable analysis, coefficient of variation> 27.8% showed a nonsignificant trend to association with 5-year rejection-free survival (HR, 1.298; 95%CI, 0.993-1.695; P=.056) and with 5-year mortality (HR, 1.387; 95%CI, 0.979-1.963; P=.065). Association with rejection became significant on analysis of only those patients without rejection episodes during the first year posttransplant (HR, 1.609; 95%CI, 1.129-2.295; P=.011). The tacrolimus-based formulation had less IPV than cyclosporine and better results with less influence of IPV.

CONCLUSIONS

IPV of calcineurin inhibitors is only marginally associated with mid-term outcomes after heart transplant, particularly with the tacrolimus-based immunosuppression, although it could play a role in the most stable recipients.

A randomized crossover study comparing different tacrolimus formulations to reduce intrapatient variability in tacrolimus exposure in kidney transplant recipients

A high intrapatient variability (IPV) in tacrolimus exposure is a risk factor for poor long‐term outcomes after kidney transplantation. The main objective of this trial was to investigate whether tacrolimus IPV decreases after switching patients from immediate‐release (IR)‐tacrolimus to either extended‐release (ER)‐tacrolimus or LifeCyclePharma (LCP)‐tacrolimus. In this randomized, prospective, open‐label, cross‐over trial, adult kidney transplant recipients on a stable immunosuppressive regimen, including IR‐tacrolimus, were randomized for conversion to ER‐tacrolimus or LCP‐tacrolimus, and for the order in which IR‐tacrolimus and the once‐daily formulations were taken. Patients were followed 6 months for each formulation, with monthly tacrolimus predose concentration assessments to calculate the IPV. The IPV was defined as the coefficient of variation (%) of dose corrected predose concentrations. Ninety‐two patients were included for analysis of the primary outcome. No significant differences between the IPV of IR‐tacrolimus (16.6%) and the combined once‐daily formulations (18.3%) were observed (% difference +1.7%, 95% confidence interval [CI] −1.1% to ‒4.5%, p = 0.24). The IPV of LCP‐tacrolimus (20.1%) was not significantly different from the IPV of ER‐tacrolimus (16.5%, % difference +3.6%, 95% CI −0.1% to 7.3%, p = 0.06). In conclusion, the IPV did not decrease after switching from IR‐tacrolimus to either ER‐tacrolimus or LCP‐tacrolimus. These results provide no arguments to switch kidney transplant recipients from twice‐daily (IR) tacrolimus formulations to once‐daily (modified‐release) tacrolimus formulations when the aim is to lower the IPV.

Effect of the Interrelation between CYP3A5 Genotype, Concentration/Dose Ratio and Intrapatient Variability of Tacrolimus on Kidney Graft Function: Monte Carlo Simulation Approach

Background: Tacrolimus (Tac) is characterized by large between- and within-patient (IPV) variability in pharmacokinetics and exposure. Aim: This study aimed to assess and validate the effect of Tac IPV and trough concentration-to-dose ratio (C0/D) over 6-12 months on reduced estimated glomerular filtration rate (eGFR) values in the late period after kidney transplantation (Tx), applying Monte Carlo (MC) simulation. Methods: The previously published linear regression was the basis for MC simulation, performed to determine how variations in significant predictors affect the distribution of eGFR from 13 to 36 months post-transplantation. The input C0/D values were derived from CYP3A5 genotype subgroups. Results: Patients characterized by high Tac IPV and low mean C0/D over 6-12 months could have been at greater risk of lower eGFR values in a three-year period following Tx compared to the other patient groups. This effect was more pronounced in patients with a lower eGFR at the 6th month and a history of acute rejection. The proven contribution of CYP3A5 expresser genotype to low C0/D values may suggest its indirect effect on long-term graft function. Conclusion: The findings indicate that simultaneous assessment of Tac IPV, C0/D, and CYP3A5 genotype may identify patients at risk of deterioration of graft function in the long-term post-transplantation period.

Review of the Preanalytical Errors That Impact Therapeutic Drug Monitoring

PURPOSE

Preanalytical errors comprise the majority of testing errors experienced by clinical laboratories and significantly impact the accuracy of therapeutic drug monitoring (TDM).

METHODS

Specific preanalytical factors in sample timing, collection, transport, processing, and storage that lead to errors in TDM were reviewed. We performed a literature search using several scientific databases including PubMed, ScienceDirect, Scopus, Web of Science, and ResearchGate for human studies published in the English language from January 1980 to February 2021, reporting on TDM and the preanalytical phase.

RESULTS

Blood collection errors (ie, wrong anticoagulant/clot activator used, via an intravenous line, incorrect time after dosing) delay testing, cause inaccurate results, and adversely impact patient care. Blood collected in lithium heparin tubes instead of heparin sodium tubes produce supertoxic lithium concentrations, which can compromise care. Specimens collected in serum separator gel tubes cause falsely decreased concentrations due to passive absorption into the gel when samples are not processed and analyzed quickly. Dried blood spots are popular for TDM as they are minimally invasive, allowing for self-sampling and direct shipping to a clinical laboratory using regular mail. However, blood collection techniques, such as trauma to the collection site, filter paper fragility, and hematocrit (Hct) bias, can adversely affect the accuracy of the results. Volumetric absorptive microsampling is a potential alternative to dried blood spot that offers fast, volume-fixed sampling, low pain tolerance, and is not susceptible to Hct concentrations.

CONCLUSIONS

The identification of preanalytical factors that may negatively impact TDM is critical. Developing workflows that can standardize TDM practices, align appropriate timing and blood collection techniques, and specimen processing will eliminate errors.

Increased renal function decline in fast metabolizers using extended-release tacrolimus after kidney transplantation

Fast metabolism of immediate-release tacrolimus (IR-Tac) is associated with decreased kidney function after renal transplantation (RTx) compared to slow metabolizers. We hypothesized, by analogy, that fast metabolism of extended-release tacrolimus (ER-Tac) is associated with worse renal function. We analyzed data from patients who underwent RTx at three different transplant centers between 2007 and 2016 and received an initial immunosuppressive regimen with ER-Tac, mycophenolate, and a corticosteroid. Three months after RTx, a Tac concentration to dose ratio (C/D ratio) < 1.0 ng/ml · 1/mL defined fast ER-Tac metabolism and ≥ 1.0 ng/ml · 1/mL slow metabolism. Renal function (estimated glomerular filtration rate, eGFR), first acute rejection (AR), conversion from ER-Tac, graft and patient survival were observed up to 60-months. 610 RTx patients were divided into 192 fast and 418 slow ER-Tac metabolizers. Fast metabolizers showed a decreased eGFR at all time points compared to slow metabolizers. The fast metabolizer group included more patients who were switched from ER-Tac (p < 0.001). First AR occurred more frequently (p = 0.008) in fast metabolizers, while graft and patient survival rates did not differ between groups (p = 0.529 and p = 0.366, respectively). Calculation of the ER-Tac C/D ratio early after RTx may facilitate individualization of immunosuppression and help identify patients at risk for an unfavorable outcome.

Quantitation of Tacrolimus in Human Whole Blood Samples Using the MITRA Microsampling Device

BACKGROUND

The calcineurin inhibitor tacrolimus is a narrow therapeutic index medication, which requires therapeutic drug monitoring to optimize dose on the basis of systemic exposure. MITRA microsampling offers a minimally invasive approach for the collection of capillary blood samples from a fingerprick as an alternative to conventional venous blood sampling for quantitation of tacrolimus concentrations.

METHODS

A bioanalytical method for the quantitation of tacrolimus in human whole blood samples collected on MITRA tips was developed, using liquid-liquid extraction followed by liquid chromatography with tandem mass spectrometry detection. Validation experiments were performed according to the current Food and Drug Administration and European Medicines Agency guidelines on validation of bioanalytical methods. Validation criteria included assay specificity and sensitivity, interference, carryover, accuracy, precision, dilution integrity, matrix effect, extraction recovery, effect of hematocrit and hyperlipidemia, and stability.

RESULTS

All assay validation results were within the required acceptance criteria, indicating a precise and accurate tacrolimus quantitation method. The validated assay range was 1.00-50.0 ng/mL. No interference, carryover or matrix effect was observed. Extraction recovery was acceptable across the assay range. Samples were stable for up to 96 days at -20°C and 20°C, and 28 days at 40°C. Hematocrit, hyperlipidemia, and lot-to-lot differences in the nominal absorption volume of the 10-μL MITRA tips were shown not to influence tacrolimus quantitation by this assay method.

CONCLUSIONS

The bioanalytical method validated in this study is appropriate and practical for the quantitation of tacrolimus in human whole blood samples collected using the MITRA microsampling device.

Impact of a pharmacist-led, mHealth-based intervention on tacrolimus trough variability in kidney transplant recipients: A report from the TRANSAFE Rx randomized controlled trial

PURPOSE

Nonadherence is a leading cause of death-censored allograft loss in kidney transplant recipients. Strong associations have tied tacrolimus intrapatient variability (IPV) to degree of nonadherence and high tacrolimus IPV to clinical endpoints such as rejection and allograft loss. Nonadherence is a dynamic, complex problem best targeted by multidimensional interventions, including mobile health (mHealth) technologies.

METHODS

This was a secondary planned analysis of a 12-month, parallel, 2-arm, semiblind, 1:1 randomized controlled trial involving 136 adult kidney transplant recipients. The primary aims of the TRANSAFE Rx study were to assess the efficacy of a pharmacist-led, mHealth-based intervention in improving medication safety and health outcomes for kidney transplant recipients as compared to usual care.

RESULTS

Patients were randomized equally to 68 patients per arm. The intervention arm demonstrated a statistically significant decrease in tacrolimus IPV over time as compared to the control arm (P = 0.0133). When analyzing a clinical goal of tacrolimus IPV of less than 30%, the 2 groups were comparable at baseline (P = 0.765), but significantly more patients in the intervention group met this criterion at month 12 (P = 0.033). In multivariable modeling, variables that independently impacted tacrolimus IPV included time, treatment effect, age, and warm ischemic time.

CONCLUSION

This secondary planned analysis of an mHealth-based, pharmacist-led intervention demonstrated an association between the active intervention in the trial and improved tacrolimus IPV. Further prospective studies are required to confirm the mutability of tacrolimus IPV and impact of reducing tacrolimus IPV on long-term clinical outcomes.

Association between medication adherence and intrapatient variability in tacrolimus concentration among stable kidney transplant recipients

This study analyzed the association between medication adherence and the intrapatient variability (IPV) of tacrolimus concentrations among kidney transplant recipients through a post hoc analysis of the dataset from a recently conducted randomized controlled trial. Among 138 patients enrolled in the original trial, 92 patients with ≥ 5 months of medication event monitoring system (MEMS) use and ≥ 4 tacrolimus trough values were included in this post hoc analysis. The variability of tacrolimus trough levels was calculated using coefficient variation (CV) and mean absolute deviation. Adherence was assessed using MEMS and self-report via the Basal Assessment of Adherence to Immunosuppressive Medication Scale. There were no statistically significant differences in the CV [median 16.5% [interquartile range 11.6–25.5%] and 16.0% [11.5–23.5%], respectively, P = .602] between the nonadherent (n = 59) and adherent groups (n = 33). There was also no significant correlation between the CV and adherence detected by MEMS (taking adherence, ρ = − 0.067, P = .527; dosing adherence, ρ = − 0.098, P = .352; timing adherence, ρ = − 0.113, P = .284). Similarly, adherence measured by self-report did not significantly affect the IPV (P = .452). In this post hoc analysis, nonadherent behavior, measured through electronic monitoring or self-report, did not affect the IPV.

Tacrolimus intrapatient variability in solid organ transplantation: A multiorgan perspective

BACKGROUND

Tacrolimus therapy in solid organ transplant (SOT) recipients is challenging due to its narrow therapeutic window and pharmacokinetic variability both between patients and within a single patient. Intrapatient variability (IPV) of tacrolimus trough concentrations has become a novel marker of interest for predicting transplant outcomes. The purpose of this review is to evaluate the association of tacrolimus IPV with graft and patient outcomes and identify interventions to improve IPV in SOT recipients.

METHODS

A systematic review of the literature was performed using PubMed and Embase from database inception to September 20, 2020. Studies were eligible only if they evaluated an association between tacrolimus IPV and transplant outcomes. Both pediatric and adult studies were included. Measures of variability were limited to standard deviation, coefficient of variation, and time in therapeutic range.

RESULTS

Forty-four studies met the inclusion criteria. Studies were published between 2008 and 2020 and were observational in nature. Majority of data were published in adult kidney transplant recipients and identified an association with rejection, de novo donor specific antibody (dnDSA) formation, graft loss, and patient survival. Evaluation of IPV-directed interventions was limited to small preliminary studies.

CONCLUSIONS

High tacrolimus IPV has been associated with poor outcomes including acute rejection, dnDSA formation, graft loss, and patient mortality in SOT recipients. Future research should prospectively explore IPV-directed interventions to improve transplant outcomes.

Ten-Year Efficacy and Safety of Once-Daily Tacrolimus in Kidney Transplant: A Prospective Cohort Study

Tacrolimus is a cornerstone in the immunosuppressive therapy of kidney transplantation. The once-daily formulation of tacrolimus has been shown to improve adherence of patients without affecting short-term efficacy. However, long-term proof of once-daily tacrolimus efficacy and safety is still lacking. From January 2009 to November 2013, 170 clinically stable kidney transplant patients were offered to change from the ongoing twice-daily tacrolimus (TDT) formulation to a once-daily tacrolimus (ODT) regimen. Kidney transplant recipients agreeing to the change to be treated with an ODT regimen (n = 105, estimated glomerular filtration rate [eGFR] 57.1 ± 1.6 mL/min/1.73 m2) and patients continuing on a TDT formulation (n = 65, eGFR 52.0 ± 2.2 mL/min/1.73 m2) were prospectively followed (median follow-up time 10.4 and 12.6 years in the ODT and TDT groups, respectively, P = not significant). At the end of the follow-up, patients in both groups experienced similar eGFR (50.4 ± 2.2 vs 48.0 ± 2.7 mL/min/1.73 m2 in the ODT and TDT groups, respectively, P = not significant). No differences were observed in biopsy-proven acute rejection, overall graft survival, doubling of serum creatinine, and new onset of proteinuria. The 2 groups also had a comparable rate of death, sepsis, and neoplasia. In conclusion, ODT appears safe and effective in stable kidney graft recipients even 10 years after transplantation. These findings support the use of ODT as a primary tacrolimus formulation in patients with kidney transplantation.

Acute and chronic kidney disease after pediatric liver transplantation: An underestimated problem

Acute and chronic kidney injuries represent critical issues after liver transplantation (LTx), but whereas renal dysfunction in adult transplant patients is well documented, little is known about its prevalence in childhood. It is a challenge to accurately evaluate renal function in patients with liver disease, due to several confounding factors. Creatinine-based equations estimating glomerular filtration rate, validated in nephropathic patients without hepatic issues, are frequently inaccurate in end-stage liver disease, underestimating the real impact of renal disease. Moreover, whereas renal issues observed within 1 year from LTx were often related to acute injuries, kidney damage observed after 5-7 years from LTx, is due to chronic, irreversible mechanisms. Most immunosuppression protocols are based on calcineurin inhibitors (CNIs) and corticosteroids, but mycophenolate mofetil or sirolimus could play significant roles, also in children. Early diagnosis and personalized treatment represent the bases of kidney disease management, in order to minimize its close relation with increased mortality. This review analyzed acute and chronic kidney damage after pediatric LTx, also discussing the impact of pre-existent renal disease. The main immunosuppressant strategies have been reviewed, highlighting their impact on kidney function. Different methods assessing renal function were reported, with the potential application of new renal biomarkers.

A comprehensive review of the impact of tacrolimus intrapatient variability on clinical outcomes in kidney transplantation

Tacrolimus (Tac) is widely used to prevent rejection and graft loss in solid organ transplantation. A limiting characteristic of Tac is the high intra and interpatient variability associated with its use. Routine therapeutic drug monitoring (TDM) is necessary to facilitate Tac management and to avoid undesirable clinical outcomes. However, whole blood trough concentrations commonly utilized in TDM are not strong predictors of the detrimental clinical outcomes of interest. Recently, researchers have focused on Tac intrapatient variability (Tac IPV) as a novel marker to better assess patient risk. Higher Tac IPV has been associated with a number of mechanisms leading to shortened graft survival. Medication nonadherence (MNA) is considered to be the primary determinant of high Tac IPV and perhaps the most modifiable risk factor. An understanding of the methodology behind Tac IPV is imperative to its recognition as an important prognostic measure and integration into clinical practice. Therapeutic interventions targeting MNA and reducing Tac IPV are crucial to improving long-term graft survival.

Fasting Status and Circadian Variation Must be Considered When Performing AUC-based Therapeutic Drug Monitoring of Tacrolimus in Renal Transplant Recipients

Therapeutic drug monitoring (TDM) is mandatory for the immunosuppressive drug tacrolimus (Tac). For clinical applicability, TDM is performed using morning trough concentrations. With recent developments making tacrolimus concentration determination possible in capillary microsamples and Bayesian estimator predicted area under the concentration curve (AUC), AUC‐guided TDM may now be clinically applicable. Tac circadian variation has, however, been reported, with lower systemic exposure following the evening dose. The aim of the present study was to investigate tacrolimus pharmacokinetic (PK) after morning and evening administrations of twice‐daily tacrolimus in a real‐life setting without restrictions regarding food and concomitant drug timing. Two 12 hour tacrolimus investigations were performed; after the morning dose and the following evening dose, respectively, in 31 renal transplant recipients early after transplantation both in a fasting‐state and under real‐life nonfasting conditions (14 patients repeated the investigation). We observed circadian variation under fasting‐conditions: 45% higher peak‐concentration and 20% higher AUC following the morning dose. In the real‐life nonfasting setting, the PK‐profiles were flat but comparable after the morning and evening doses, showing slower absorption rate and lower AUC compared with the fasting‐state. Limited sampling strategies using concentrations at 0, 1, and 3 hours predicted AUC after fasting morning administration, and samples obtained at 1, 3, and 6 hours predicted AUC for the other conditions (evening and real‐life nonfasting). In conclusion, circadian variation of tacrolimus is present when performed in patients who are in the fasting‐state, whereas flatter PK‐profiles and no circadian variation was present in a real‐life, nonfasting setting.

Number of Regularly Prescribed Drugs and Intrapatient Tacrolimus Trough Levels Variability in Stable Kidney Transplant Recipients

High intra-patient variability (IPV) of tacrolimus levels is associated with poor long-term outcome after transplantation. We aimed to evaluate whether the number of regularly prescribed medications is associated with the tacrolimus IPV. We have studied 152 kidney transplant recipients (KTRs) with mean post-transplant time of 6.0 ± 3.1 years. The coefficient of variation (CV) as a measure of IPV was calculated in each individual patient. Data concerning the type and number of currently prescribed medications were collected. The participants were divided into four groups, based on the number of regularly prescribed drugs (≤3, 4-6, 7-9, ≥10 drugs, respectively). There was an increasing trend for median CV, proportional to the increasing number of medications [group 1: 0.11 (interquartile range, 0.08-0.14), group 2: 0.14 (0.01-0.17), group 3: 0.17 (0.14-0.23), group 4: 0.17 (0.15-0.30); p value for trend = 0.001]. Stepwise backward multivariate regression analysis revealed that the number of medications [partial correlation coefficient (rpartial) = 0.503, p < 0.001] independently influenced the tacrolimus IPV. Concomitant steroid or diuretics use increased IPV only in Advagraf-treated KTRs, whereas proton-pump inhibitor or statin use increased IPV in the Prograf group but not in the Advagraf group. A large number of concomitant medications significantly increases the tacrolimus IPV in stable KTRs.

Once-Daily versus Twice-Daily Tacrolimus in Kidney Transplantation: A Systematic Review and Meta-analysis of Observational Studies

BACKGROUND

Tacrolimus is the most commonly prescribed medication in initial immunosuppressive regimens to prevent acute rejection in kidney transplant recipients (KTRs). Tacrolimus was originally available as an immediate-release formulation (IR-Tac) given twice daily. Extended-release tacrolimus (ER-Tac) given once daily was later developed with the expectation of improved medication adherence. Data from observational studies, which compared outcomes between ER-Tac and IR-Tac in different populations of KTRs including those who are unlikely to be enrolled in randomized clinical trials, have been reported.

PURPOSE

To evaluate the incidence of biopsy-proven acute rejection (BPAR) at 12 months together with other outcomes reported in observational studies among adult KTRs who received ER-Tac compared to IR-Tac.

METHODS

In accordance with the recommendations of the Cochrane Collaboration and the Meta-analysis of Observational Studies in Epidemiology, we systematically reviewed all observational studies that compared clinical outcomes between ER-Tac and IR-Tac in KTRs. The systematic searches were conducted on PubMed, EMBASE, Scopus, and Web of Science without language restriction. Reference lists were also searched and reviewed. Data were extracted for BPAR, graft survival, patient survival, estimated glomerular filtration rate (eGFR), serum creatinine (Scr), creatinine clearance (CrCl), at different times after kidney transplantation (KT). A meta-analysis was performed to integrate the results from the eligible studies. This study is registered with PROSPERO, number CRD42019135705.

RESULTS

From the 1401 articles screened, 10 observational studies in KTRs who received tacrolimus were included. The pooled results showed significantly lower BPAR with ER-Tac than with IR-Tac at 12 months post-KT (5 studies, n = 659; RR, 0.69; 95% CI 0.51-0.95; p = 0.02; I² = 0%). No significant differences in BPAR at other time points after KT were found. Graft survival, patient survival, Scr, and eGFR were comparable between groups at different times over approximately 1 year after transplantation.

CONCLUSIONS

Based upon currently available evidence in observational studies, 30% lower risk of BPAR was observed in ER-Tac group compared with IR-Tac group at 12 months post-KT, while there was no significant difference in BPAR risk at any other studied time points. No differences in graft- and patient-survival rates and kidney function were found. Given the limitations of observational studies to make causal inference, as well as quality limitations among the included studies, caution should be exercised in interpreting these findings.

Non-linear Relationship between Tacrolimus Blood Concentration and Acute Rejection After Kidney Transplantation: A Systematic Review and Dose-Response Meta-Analysis of Cohort Studies

BACKGROUND

Maintaining the exposure of tacrolimus (Tac) after kidney transplantation (KT) must be necessary to prevent acute rejection (AR) and improve graft survival，but there is still no clear consensus on the optimal Tac target blood concentration and concentration-effect relationship is poorly defined.

METHODS

We conducted a dose-response meta-analysis to quantitatively assess the association between Tac blood concentration and (AR) or adverse effects after KT. A comprehensive search of PubMed, Embase and Cochrane library databases was conducted to find eligible studies up to 10th September 2018. Unpublished data from patients receiving KT in West China Hospital (Sichuan University, China) were also collected. Both twostage dose-response and one-stage dose-response meta-analysis models were used to improve the statistical power.

RESULTS

A total of 4967 individuals from 10 original studies and 1453 individuals from West China Hospital were eligible for the ultimate analysis. In the two-stage dose-response meta-analysis model, we observed a significant non-linear relationship between Tac blood concentration and AR (P < 0.001) with moderate heterogeneity (I2 = 46.0%, P = 0.08). Tac blood concentration at 8ng/ml was associated with the lowest risk of AR (RR: 0.26, 95%CI: 0.13 - 0.54) by reference to 2ng/ml. Tac concentration at 7.0 - 11.0 ng/ml reduced the risk of AR by at least 70%, 5-14 ng/ml by at least 60%, and 4.5 - 14 ng/ml at least 50%. In the one-stage dose-response model, we also found a strong non-linear relationship between Tac and AR (P < 0.001) with moderate heterogeneity (I2 = 41.2%, P = 0.10). Tac concentration of 7.5 ng/ml was associated with the lowest risk of AR (RR: 0.35, 95%CI: 0.16 - 0.77). The blood concentration at 5.5 - 9.5 ng/ml was associated with the reduced AR by at least 60% and 4.5 - 10.5 ng/ml by at least 50% by reference to 2 ng/ml.

CONCLUSION

Maintaining Tac blood concentration at 5 - 9.5 ng/ml within the first year may prevent AR most effectively.

Trough Level and Tacrolimus Variability of Early Converted Once-Daily Tacrolimus: 1-Year Follow-up Study

INTRODUCTION

Long-term transplant outcomes are considered a crucial point for kidney transplantation. Follow-up studies in patients receiving early conversion to once-daily tacrolimus (TAC-OD) are still limited. We aimed to investigate tacrolimus trough level (C_min), intrapatient variability of tacrolimus dose-normalized C_min (TAC-C_min/D), along with other outcomes between twice-daily tacrolimus (TAC-BID) and early converted TAC-OD.

MATERIAL AND METHODS

This study was a single center, retrospective, cohort study. All new kidney transplant patients who received tacrolimus and presented an estimated glomerular filtration rate of more than 45 mL/min/1.73 m² on the day of hospital discharge were included. Studied patients were divided into the standard TAC-BID and patients who were converted from TAC-BID to TAC-OD on the day of hospital discharge. We followed patients for 1 year after transplantation.

RESULTS

At the first follow-up visit, C_min of TAC-OD was significantly lower than that of TAC-BID. However, C_min and estimated glomerular filtration rate were comparable between TAC-BID and TAC-OD throughout 1-year follow-up. TAC-OD also provided a lower intrapatient variability of TAC-C_min/D compared with TAC-BID when observed after 6 months post transplantation (17.40% and 23.27% for TAC-OD and TAC-BID, respectively; P = .13). The renal function, as well as other adverse outcomes, was similar between 2 formulations.

DISCUSSION

TAC-OD provided a similar C_min with comparable renal function compared with TAC-BID during 1-year follow-up. In addition, TAC-OD is likely to have a benefit of a lower intrapatient variability of tacrolimus.

CONCLUSION

Early conversion from TAC-BID to TAC-OD with 1:1 ratio can be used with close long-term monitoring.

Optimization of tacrolimus in kidney transplantation: New pharmacokinetic perspectives

Tacrolimus is the cornerstone of immunosuppressive therapy after kidney transplantation (KT), but its use is complicated by a narrow therapeutic index and high inter- and intra-patient pharmacokinetic variability. There are three available oral formulations of tacrolimus: immediate-release tacrolimus (IR-Tac), extended-release tacrolimus (ER-Tac) and a MeltDose® (LCPT) formulation, the latter favoring a prolonged drug release and increased bioavailability. The time-concentration curves of these formulations are different. Compared with IR-Tac and ER-Tac, LCPT has a relatively flat pharmacokinetic profile with less fluctuation between trough and peak exposures, and a delayed peak concentration. This translates to a more stable delivery of tacrolimus and may alleviate the risk of underexposure and allograft rejection or overexposure and toxicity. The once-daily formulation of both ER-TAC and LCPT may also offer a potential advantage on patient adherence. Fast metabolizers of tacrolimus, the elderly, and human leukocyte antigen-sensitized patients are at risk of poorer outcomes after KT, possibly associated with a different exhibited pharmacokinetics of tacrolimus or different requirements in terms of exposure. Simple, practical strategies are needed to identify patients at risk of suboptimal KT outcomes and those who would benefit from a more proactively personalized approach to tacrolimus treatment. This review aims to increase awareness of the link between the pharmacokinetics of oral tacrolimus formulations and the clinical needs of patients after KT, particularly among those who have clinically significant pharmacokinetic variation of tacrolimus.

Long-Term Kidney Transplant Outcomes: Role of Prolonged-Release Tacrolimus

Tacrolimus has significantly improved outcomes for kidney transplant patients and remains the cornerstone of immunosuppressive therapy. While improvements in short-term outcomes in transplantation have been achieved in recent years, maintaining long-term graft survival remains a challenge in kidney transplantation. Minimizing risk factors for poor long-term kidney graft function and survival, and modifying tacrolimus regimens in the early and maintenance phases post-transplantation are essential to maintain long-term kidney transplant outcomes. Tacrolimus has a narrow therapeutic window, resulting in a tightly defined range of optimal drug exposure. Underimmunosuppression is associated with long-term risks, such as the development of donor-specific antibodies and antibody-mediated rejection, with a high possibility of a decline in kidney function and progression to graft failure. Conversely, prolonged overimmunosuppression carries a risk of drug-related adverse events. This review provides an overview of the differences in the formulation, delivery, and pharmacokinetic profiles between immediate- and prolonged-release tacrolimus and evaluates the effect of prolonged-release tacrolimus on the risk factors for poor outcomes in kidney transplantation. Recent evidence is used to provide guidance on target tacrolimus trough levels in the early and maintenance phases post-transplantation, with a view to improving long-term kidney graft function.

Long-term, prolonged-release tacrolimus-based immunosuppression in de novo kidney transplant recipients: 5-year prospective follow-up of the ADHERE study patients

The objectives of this study were to assess long-term graft survival, patient survival, renal function, and acute rejections in de novo kidney transplant recipients, treated with once-daily prolonged-release tacrolimus-based therapy. The study was a 5-year non-interventional prospective follow-up of patients from the ADHERE study, a Phase IV 12-month open-label assessment of patients randomized to receive prolonged-release tacrolimus in combination with mycophenolate mofetil (MMF) (Arm 1) or sirolimus (Arm 2). From 838 patients in the randomized study, 587 were included in the long-term follow-up, of whom 510 completed the study at year 5. At 1 year post-transplant, graft and patient survival rates were 93.0% and 97.8%, respectively, and at 5 years were 84.0% and 90.8%, respectively. Cox proportional hazards analysis showed no association between graft loss, initial randomized treatment arm, donor age, donor type, or sex. The 5-year acute rejection-free survival rate was 77.4%, and biopsy-confirmed acute rejection-free survival rate was 86.0%. Renal function remained stable over the follow-up period: mean ± SD eGFR 4-variable modification diet in renal disease formula (MDRD4) was 52.3 ± 21.6 ml/min/1.73 m² at 6 months and 52.5 ± 23.0 ml/min/1.73 m² at 5 years post-transplant. These findings support the role of long-term once-daily prolonged-release tacrolimus-based immunosuppression, in combination with sirolimus or MMF, for renal transplant recipients in routine clinical practice.

Intrapatient Variability of Tacrolimus Exposure in Solid Organ Transplantation: A Novel Marker for Clinical Outcome

The calcineurin-inhibitor tacrolimus (Tac) provides an acceptable balance between prevention of allograft rejection and drug-related adverse effects, making it the standard of care in all types of solid organ transplantation for the last 2 decades. Recent data have demonstrated that high intrapatient variability (IPV) in Tac predose trough concentrations has deleterious effects on allograft survival. The underlying mechanisms by which a high Tac IPV shortens allograft survival are acute and chronic rejection, donor-specific anti-HLA antibodies, and progressive fibrotic damage to the graft. Modifiable causes of high Tac IPV include medication nonadherence (MNA), drug interactions, nutritional interferences, and concurrent diseases. Recognizing high Tac IPV as an important prognostic risk factor after solid organ transplantation requires understanding of the definitions, the use of correct diagnostic metrics, and methodology. Therapeutic interventions aimed at reducing Tac IPV are targeted on improving MNA, avoiding or adjusting drug interactions, drug dosing assists, and educational support of recipients.

Efficacy and safety of tacrolimus in de novo pediatric transplant recipients randomized to receive immediate- or prolonged-release tacrolimus

BACKGROUND AND AIMS

This multicenter trial compared immediate-release tacrolimus (IR-T) vs prolonged-release tacrolimus (PR-T) in de novo kidney, liver, and heart transplant recipients aged <16 years. Each formulation had similar pharmacokinetic (PK) profiles. Follow-up efficacy and safety results are reported herein.

MATERIALS AND METHODS

Patients, randomized 1:1, received once-daily, PR-T or twice-daily, IR-T within 4 days of surgery. After a 4-week PK assessment, patients continued randomized treatment for 48 additional weeks. At Year 1, efficacy assessments included the number of clinical acute rejections, biopsy-confirmed acute rejection (BCAR) episodes (including severity), patient and graft survival, and efficacy failure (composite of death, graft loss, BCAR, or unknown outcome). Adverse events were assessed throughout.

RESULTS

The study included 44 children. At Year 1, mean ± standard deviation tacrolimus trough levels were 6.6 ± 2.2 and 5.4 ± 1.6 ng/mL, and there were 2 and 7 acute rejection episodes in the PR-T and IR-T groups, respectively. No cases of graft loss or death were reported during the study. The overall efficacy failure rate was 18.2% (PR-T n = 1; IR-T n = 7).

CONCLUSIONS

In pediatric de novo solid organ recipients, the low incidence of BCAR and low efficacy failure rate suggest that PR-T-based immunosuppression is effective and well tolerated to 1-year post-transplantation.

A non-randomized trial of conversion from ciclosporin and tacrolimus to tacrolimus MR4 in stable long-term kidney transplant recipients: Graft function and influences of ABCB1 genotypes

TRIAL REGISTRATION

PEP Study: Ethics committee N° 393/2004, EudraCT 2004-004209-98. PEP-X Study: Ethics committee amendment application N° 154/01/2008. ClinicalTrials.gov NCT03751332.

Efficacy and safety of prolonged-release versus immediate-release tacrolimus inde novoliver transplant recipients in South Korea: a randomized open-label phase 4 study (MAPLE)

Background

Prolonged-release tacrolimus is associated with better long-term graft and patient survival than the immediate-release formulation in liver transplant patients. However, no clinical data are available to assess the efficacy and safety of early conversion from twice-daily, immediate-release tacrolimus to once-daily, prolonged-release tacrolimus in de novo liver transplant recipients in Korea.

Methods

A 24-week, randomized, open-label study was conducted in 36 liver transplant recipients. All patients received immediate- release tacrolimus (0.1–0.2 mg/kg/day, divided into two doses) for 4 weeks after transplantation, at which time 50% of the patients were converted, at a ratio of 1 mg to 1 mg, to prolonged-release tacrolimus (once-daily). The primary efficacy endpoint was the incidence of biopsy-confirmed acute rejection (BCAR) from weeks 4 to 24 after transplantation (per-protocol set). Medication adherence, adverse event profiles, laboratory tests, vital signs, and physical changes were also recorded.

Results

BCAR frequency at 24 weeks was similar between the two treatment groups; two cases (mean±standard deviation, 0.14±0.53 cases) of BCAR were reported in one patient treated with prolonged-release tacrolimus (n=14), while no such cases were reported among patients treated with immediate-release tacrolimus (n=12). The tacrolimus blood concentration at weeks 12 and 24, medication adherence, and adverse event profiles were also similar between the formulations, with no unusual laboratory test results, vital signs, or physical changes reported.

Conclusions

Early conversion to a simplified, once-daily, prolonged-release tacrolimus regimen may be an effective treatment option for liver transplant recipients in Korea. Larger-scale studies are warranted to confirm non-inferiority to immediate-release tacrolimus formulation in de novo liver transplant recipients.

Real-World Study of Once-Daily, Extended-Release Tacrolimus Versus Twice-Daily, Immediate-Release Tacrolimus in Kidney Transplantation: Clinical Outcomes and Healthcare Resource Utilization

INTRODUCTION

Real-world data with extended-release tacrolimus (ER-T) are lacking in the USA. This study examined clinical outcomes and healthcare resource utilization in kidney transplant patients receiving ER-T in clinical practice.

METHODS

This was a retrospective, single-center analysis (February-June 2016) using data from Northwestern University's Enterprise Data Warehouse. Adult patients receiving a kidney transplant in the preceding 4 years, treated de novo or converted to ER-T from immediate-release tacrolimus (IR-T) within 10 days post-transplantation, and maintained on ER-T (at least 3 months) were included. Patients were matched for demographic and clinical characteristics with IR-T-treated control patients. Endpoints included clinical outcomes and healthcare resource utilization up to 1 year post-transplantation.

RESULTS

A total of 19 ER-T-treated patients were matched with 55 IR-T-treated patients. No ER-T-treated patients experienced biopsy-confirmed acute rejection (BCAR) or graft failure versus 3 (5.5%) and 3 (5.5%) IR-T-treated patients, respectively. Mean estimated glomerular filtration rate (eGFR), the number of all-cause outpatient visits, readmissions, and all-cause hospitalization days were comparable between groups. Tacrolimus trough levels, days to target level (6-10 ng/mL), and number of required dose adjustments were also similar.

CONCLUSION

Real-world clinical outcomes and healthcare resource utilization were similar with ER-T and IR-T. Larger studies will need to investigate the trend toward fewer BCAR events, and increased graft survival with ER-T.

FUNDING

Astellas Pharma Global Development, Inc. Plain language summary available for this article.

Comparative pharmacokinetics of tacrolimus in stable pediatric allograft recipients converted from immediate-release tacrolimus to prolonged-release tacrolimus formulation

This study was a Phase II, open-label, multicenter, single-arm, cross-over study comparing the pharmacokinetics (PK) of tacrolimus in stable pediatric kidney, liver, or heart allograft recipients converted from immediate-release tacrolimus (IR-T) to prolonged-release tacrolimus (PR-T). In Days -30 to -1 of screening period, patients received their IR-T-based regimen; during Days 1-7, patients received study IR-T (same dose as screening). On Day 7, the first 24-hours PK profile was taken; patients were then converted to PR-T (1 mg:1 mg), with a second 24-hours PK profile taken on Day 14. The primary end-point was tacrolimus area under the blood concentration-time curve over 24 hours (AUC₂₄ ); secondary end-points were maximum concentration C_max and concentration at 24 hours C₂₄ . The predefined similarity interval for confidence intervals (CIs) of least squares mean (LSM) ratios was 80%-125%. The PK analysis set comprised 74 pediatric transplant recipients (kidney, n = 45; liver, n = 28; heart, n = 1). PR-T:IR-T LSM ratio (90% CI) was similar overall for AUC₂₄ , _max , and C₂₄ , and for kidney and liver recipients for AUC₂₄ (LSM ratio, kidney 91.8%; liver 104.1%) and C₂₄ (kidney 90.5%; liver 89.9%). Linear relationship was similar between AUC₂₄ and C₂₄ , and between PR-T and IR-T (rho 0.89 and 0.84, respectively), suggesting that stable pediatric transplant recipients can be converted from IR-T to PR-T at the same total daily dose, using the same therapeutic drug monitoring method.

Association of Intrapatient Variability of Tacrolimus Concentration With Early Deterioration of Chronic Histologic Lesions in Kidney Transplantation

Supplemental Digital Content is available in the text.

High intrapatient variability (IPV) of tacrolimus (Tac) is increasingly recognized as a risk factor for poor graft outcomes in kidney transplantation. The timing of onset of its impact on kidney histologic lesions has not been investigated.

Assessment of tacrolimus intrapatient variability in stable adherent transplant recipients: Establishing baseline values

The purpose of this study was to determine the intrapatient (within the same patient) variability of tacrolimus in adherent patients. Daily tacrolimus trough levels were obtained at home using dried blood spot technology in kidney and liver transplant recipients. Patients were randomized to receive 3 formulations of tacrolimus, each for two 1-week periods. Adherence was monitored by patient diary, pill counts, and use of the Medication Event Monitoring System (MEMS). Variability was quantified as the coefficient of variation (CV). Comparison of CV between groups was by independent t test or one-way ANOVA as appropriate. The population was found to be adherent with a rate of 99.9% with a mean interval between the evening and morning dose of tacrolimus of 11.86 hours. The median CV for the entire population was 15.2% (range 4.8%-110%). There were no differences in CV by allograft type or tacrolimus formulation. The multivariate analysis did not identify any demographic characteristics associated with a CV > 30%. In a highly adherent population, tacrolimus did not display high intrapatient variability. Given the association between IPV and poor allograft outcomes, future studies are needed to quantitate the influence of adherence and establish target IPV goals.

Safety and Efficacy of Reduced Prolonged-release Tacrolimus Exposure in De Novo Kidney Transplantation: A Randomized, Open-label, Pilot Study in Asia-OPTIMIZE Study

Background

A multicenter, randomized, open-label, parallel group, pilot, 52-week study in Asian countries that assessed the renal function, efficacy, and safety of reduced-exposure versus standard-exposure prolonged-release tacrolimus (PR-T) in adult kidney transplant recipients (KTRs).

Methods

Posttransplantation, KTRs received PR-T from weeks 0 to 4 (initial dose, 0.2-0.3 mg/kg; target trough level, 6-10 ng/mL). At week 4, KTRs were randomized (1:1) to receive reduced-exposure PR-T (target 4-6 ng/mL, weeks 4-12; 3-5 ng/mL, weeks 12-52) or standard-exposure PR-T (target: 6-10 ng/mL, weeks 4-52). Primary end point: estimated glomerular filtration rate (eGFR) over 52 weeks. Secondary end points (week 52) included creatinine clearance, serum creatinine, graft/patient survival, biopsy-confirmed acute rejection (AR), composite of graft loss/patient death/biopsy-confirmed AR, and steroid-resistant AR. Treatment-emergent adverse events were recorded.

Results

Sixty-six KTRs received PR-T (reduced-exposure, n = 32; standard-exposure, n = 34) and were analyzed. After per-protocol dose adjustment, mean ± standard deviation tacrolimus trough level was lower with reduced- versus standard-exposure PR-T (week 52, 4.5 ± 1.1 ng/mL vs 8.0 ± 2.2 ng/mL). In the reduced- versus standard-exposure group, eGFR was similar at weeks 8 to 52 (overall least-square mean difference, -2.82; 95% confidence interval, -7.91 to 2.27; P = 0.272). At week 52, there was no significant difference in creatinine clearance (P = 0.375) or serum creatinine (P = 0.547) between groups. All grafts/patients survived, no steroid-resistant AR was reported, and 4 and 3 patients had AR in reduced- and standard-exposure groups, respectively. Drug-related treatment-emergent adverse events were reported in 34.4% and 38.2% of patients, respectively.

Conclusions

Reducing exposure to PR-T resulted in a clinically acceptable short-term safety profile and was generally as effective as standard tacrolimus exposure for Asian patients.

Envarsus, a novelty for transplant nephrologists: Observational retrospective study

The aim of this study was to evaluate the trough concentrations (Cp_trough) and the tacrolimus dosage regimen after the conversion of Prograf or Advagraf to Envarsus (new pharmaceutical form with MeltDose technology that improves the absorption of fat-soluble drugs) in patients with stable renal transplantation, and their renal function. We selected stable renal transplant patients who were converted to Envarsus. Two periods were defined: Baseline and Conversion (Envarsus) and they were stratified according to the pharmaceutical form used in the Baseline period. Sixty-one patients were included (24 with Advagraf and 37 with Prograf), with an average age of 52years. The mean post-transplant time at the time of conversion to Envarsus was 76.3months and the mean follow-up in the Baseline and Conversion period was 10.1months and 11.6months, respectively. In the Prograf and Envarsus group, the Cp_trough medians were 6.6 vs 6.4 ng/mL (P=.636), with a mean daily dose that decreased significantly from 3mg to 2mg (P<.001), respectively, maintaining the filtration rate. The median Cp_trough values in the Advagraf and Envarsus groups were 5.7ng/mL and 6.3ng/mL (P=.07), with a median daily dose of 7mg and 4mg (P<.001), respectively, and the same renal function. In stable renal transplant patients, the conversion from Advagraf to Envarsus has allowed the dose of tacrolimus to be reduced by 42.9% and, in the case of Prograf, by 33.3%, maintaining similar Cp_trough values, without renal function being altered.

High Calcineurin Inhibitor Intrapatient Variability Is Associated With Renal Allograft Inflammation, Chronicity, and Graft Loss

Background

High calcineurin inhibitor (CNI) intrapatient variability (IPV) has been associated with poor kidney allograft outcomes. However, the relationship between early allograft histological changes, their progression, and CNI-IPV is less well studied. Hence, we evaluated effect of CNI-IPV defined by the degree of fluctuation of CNI levels in all kidney transplant patients over 2 to 12 months posttransplant on early allograft inflammation, subsequent chronicity, and later clinical outcomes.

Methods

Two hundred eighty-six patients transplanted from January 2013 to November 2014 were enrolled with protocol and indication biopsies. The mean CNI-IPV was 28.5% and a quarter of our cohort had IPV of 35% or greater (high CNI IPV). Baseline demographic differences were similar between high and low CNI IPV groups.

Results

High CNI-IPV was associated with a higher incidence of acute rejection (AR) within 1 year (52% vs 31% P < 0.001), more persistent/recurrent AR by 1 year (18.2% vs 6.2%, P = 0.002), higher-grade AR (≥Banff 1B, 27.5% vs 7.3%, P < 0.001), and worse interstitial fibrosis/tubular atrophy (P = 0.005). High CNI-IPV was associated with increased graft loss (GL) and impending graft loss (iGL, defined as eGFR<30 ml/min and >30% decline in eGFR from baseline), regardless of donor-specific antibody, delayed graft function, rejection, or race. In a multivariate Cox Proportional Hazards Model, high CNI-IPV was independently associated with GL + iGL (hazard ratio, 3.1; 95% confidence interval, 1.6-5.9, P < 0.001).

Conclusions

High CNI-IPV within 1 year posttransplant is associated with higher incidence of AR, severe AR, allograft chronicity, GL, and iGL. This represents a subset of patients who are at risk for poor kidney transplant outcomes and potentially a modifiable risk factor for late allograft loss.