Defining a threshold for tacrolimus intra-patient variability associated with late acute cellular rejection in paediatric kidney transplant recipients

Tacrolimus intra-patient variability measures and its associations with allograft clinical outcomes in kidney transplantation

AIMS

Tacrolimus (Tac) is commonly prescribed in solid organ transplantation to prevent immune-mediated damage to the graft. However, its pharmacokinetics show substantial variability between and within patients. Intra-patient variability of tacrolimus (Tac-IPV) has emerged as a novel marker to predict transplant outcomes. Numerous studies report varying associations between Tac-IPV and clinical outcomes, with Tac-IPV measures showing wide discrepancies among these studies. This inconsistency could be a significant factor that influences the various outcomes reported in different studies. Our review comprehensively assesses the relationship between various Tac-IPV measures and their associations with clinical outcomes in transplant patients.

METHODS

A comprehensive literature search was conducted using the PubMed and Embase databases, covering the period from 2004 to March 31, 2023. The search focused on studies that examined the relationship between Tac-IPV and clinical outcomes in kidney transplantation (KT). The inclusion criteria were specific to studies addressing Tac-IPV, including measures such as standard deviation (SD), coefficient of variation (CV), time-weighted coefficient of variability (CV), mean absolute deviation (MAD), and Tac variability score (TVS). Clinical outcomes included the development of de novo donor-specific antibodies (dnDSA), rejection episodes, graft loss, and graft failure.

RESULTS

Among the 33 studies that met the inclusion criteria, a notable proportion presented conflicting findings in their assessment of various Tac-IPV measures regarding dnDSA, rejection episodes, graft loss, and graft failure.

CONCLUSIONS

Most studies have identified a correlation between high Tac-IPV and poor clinical outcomes; however, this relationship is multifactorial. Influencing factors include the metabolic status of KT patients, the timing of Tac-IPV calculations, and the criteria for defining high and low Tac-IPV thresholds, including the size and selection method. CV, MAD, and TWCV are the metrics that are most frequently used to determine Tac-IPV. Additionally, most of the methods for establishing Tac-IPV thresholds typically employ receiver operating characteristic (ROC) curves and median values. It is also notable that studies examining the clinical significance of Tac-IPV often include tacrolimus levels measured six months after kidney transplantation.

Molecular HLA mismatching for prediction of primary humoral alloimmunity and graft function deterioration in paediatric kidney transplantation

Introduction

Rejection remains the main cause of allograft failure in paediatric kidney transplantation and is driven by donor-recipient HLA mismatching. Modern computational algorithms enable assessment of HLA mismatch immunogenicity at the molecular level (molecular-mismatch, molMM). Whilst molMM has been shown to correlate with alloimmune outcomes, evidence demonstrating improved prediction performance against traditional antigen mismatching (antMM) is lacking.

Methods

We analysed 177 patients from the CERTAIN registry (median follow-up 4.5 years). molMM scores included Amino-Acid-Mismatch-Score (AAMS), Electrostatic-Mismatch-Score (EMS3D) and netMHCIIpan (netMHC1k: peptide binding affinity ≤1000 nM; netMHC: binding affinity ≤500 nM plus rank <2%). We stratified patients into high/low-risk groups based on risk models of DSA development.

Results

Donor-specific HLA antibodies (DSA) predominantly targeted the highest scoring molMM donor antigen within each HLA locus. MolMM scores offered superior discrimination versus antMM in predicting de novo DSA for all HLA loci; the EMS3D algorithm had particularly consistent performance (area under the receiver operating characteristic curve (AUC) >0.7 for all HLA loci vs. 0.52-0.70 for antMM). ABMR (but not TCMR) was associated with HLA-DQ molMM scores (AAMS, EMS3D and netMHC). Patients with high-risk HLA-DQ molMM had increased risk of graft function deterioration (50% reduction in baseline eGFR (eGFR50), adjusted HR: 3.5, 95% CI 1.6-8.2 high vs. low EMS3D). Multivariable modelling of the eGFR50 outcome using EMS3D HLA-DQ stratification showed better discrimination (AUC EMS3D vs. antMM at 2 years: 0.81 vs. 0.77, at 4.5 years: 0.72 vs. 0.64) and stratified more patients into the low-risk group, compared to traditional antMM.

Conclusion

Molecular mismatching was superior to antigen mismatching in predicting humoral alloimmunity. Molecular HLA-DQ mismatching appears to be a significant prognostic factor for graft function deterioration in paediatric kidney transplantation.

Effects of tacrolimus intrapatient variability and CYP3A5 polymorphism on the outcomes of pediatric kidney transplantation

BACKGROUND

The intrapatient variability (IPV) of tacrolimus (Tac) is associated with the long-term outcome of kidney transplantation. The CYP3A single-nucleotide polymorphism (SNP) may affect the IPV of Tac. We investigated the impact of IPV and genetic polymorphism in pediatric patients who received kidney transplantation.

METHODS

A total of 202 pediatric renal transplant recipients from 2000 to 2016 were analyzed retrospectively. The IPV was calculated between 6 and 12 months after surgery. Among these patients, CYP3A5 polymorphism was analyzed in 67 patients.

RESULTS

The group with high IPV had a significantly higher rate of de novo donor-specific human leukocyte antigen antibodies (dnDSA) development (35.7% vs. 16.7%, p = .003). The high IPV group also had a higher incidence of T-cell-mediated rejection (TCMR; p < .001). The high IPV had no significant influence on Epstein-Barr virus, cytomegalovirus, and BK virus viremia but was associated with the incidence of posttransplant lymphoproliferative disorders (p = .003). Overall, the graft survival rate was inferior in the high IPV group (p < .001). The CYP3A5 SNPs did not significantly affect the IPV of Tac. In the CYP3A5 expressor group, however, the IPV was significantly associated with the TCMR-free survival rate (p < .001).

CONCLUSION

The IPV of Tac had a significant impact on dnDSA development, occurrence of acute TCMR, and graft failure in pediatric patients who received renal transplantation. CYP3A5 expressors with high IPV of Tac showed worse outcomes, while the CYP3A5 polymorphism had no impact on IPV of Tac.

Patterns in Tacrolimus Variability and Association with De Novo Donor-Specific Antibody Formation in Pediatric Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

High tacrolimus intrapatient variability has been associated with inferior graft outcomes in patients with kidney transplants. We studied baseline patterns of tacrolimus intrapatient variability in pediatric patients with kidney transplants and examined these patterns in relation to C1q-binding de novo donor-specific antibodies.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

All tacrolimus levels in participants who underwent kidney-only transplantation at a single pediatric center from 2004 to 2018 (with at least 12-month follow-up, followed until 2019) were analyzed to determine baseline variability. Intrapatient variability was defined using the coefficient of variation (SD/mean ×100%) of all samples in a 6-month moving window. Routine de novo donor-specific antibody measurements were available for a subgroup of patients transplanted in 2010-2018. Cox proportional hazards models using tacrolimus intrapatient variability as a time-varying variable were used to examine the association between intrapatient variability and graft outcomes. The primary outcome of interest was C1q-binding de novo donor-specific antibody formation.

RESULTS

Tacrolimus intrapatient variability developed a steady-state baseline of 30% at 10 months post-transplant in 426 patients with a combined 31,125 tacrolimus levels. Included in the outcomes study were 220 patients, of whom 51 developed C1q-binding de novo donor-specific antibodies. De novo donor-specific antibody formers had higher intrapatient variability, with a median of 38% (interquartile range, 28%-48%) compared with 28% (interquartile range, 20%-38%) for nondonor-specific antibody formers (P<0.001). Patients with high tacrolimus intrapatient variability (coefficient of variation >30%) had higher risk of de novo donor-specific antibody formation (hazard ratio, 5.35; 95% confidence interval, 2.45 to 11.68). Patients in the top quartile of tacrolimus intrapatient variability (coefficient of variation >41%) had the strongest association with C1q-binding de novo donor-specific antibody formation (hazard ratio, 11.81; 95% confidence interval, 4.76 to 29.27).

CONCLUSIONS

High tacrolimus intrapatient variability was strongly associated with de novo donor-specific antibody formation.

Association of intraindividual tacrolimus variability with de novo donor-specific HLA antibody development and allograft rejection in pediatric kidney transplant recipients with low immunological risk

BACKGROUND

Tacrolimus (Tac) intraindividual variability (TacIPV) in pediatric kidney transplant patients is only poorly understood. We investigated the impact of TacIPV on de novo donor-specific HLA antibodies (dnDSA) development and allograft rejection in Caucasian pediatric recipients of a living or deceased donor kidney with low immunological risk.

METHODS

This was a single-center retrospective study including 48 pediatric kidney transplant recipients. TacIPV was calculated based on coefficient of variation (CV%) 6-12 months posttransplant. TacIPV cutoff was set at the median (25%). Outcome parameters were dnDSA development and rejection episodes.

RESULTS

In total, 566 Tac levels were measured with median 11.0 (6.0-17.0) measurements per patient. The cutoff of 25% corresponded to the median CV% in our study cohort (25%, IQR 18-35%) and was comparable to cutoffs determined by receiver operating characteristic (ROC) curve analysis. High TacIPV was associated with higher risk of dnDSA development (HR 3.4, 95% CI 1.0-11.1, P = 0.047; Kaplan-Meier analysis P = 0.018) and any kind of rejection episodes (HR 4.1, 95% CI 1.1-14.8, P = 0.033; Kaplan-Meier analysis P = 0.010). There was a clear trend towards higher TacIPV below the age of 6 years. TacIPV (CV%) was stable over time. A TacIPV (CV%) cutoff of 30% or IPV quantification by mean absolute deviation (MAD) showed comparable results.

CONCLUSIONS

High TacIPV is associated with an increased risk of dnDSA development and rejection episodes > year 1 posttransplant even in patients with low immunological risk profile. Therefore, in patients with high TacIPV, potential causes should be addressed, and if not resolved, changes in immunosuppressive therapy should be considered. A higher resolution version of the Graphical abstract is available as Supplementary information.

Long-term outcomes after kidney transplant failure and variables related to risk of death and probability of retransplant: Results from a single-center cohort study in Brazil

Background

Returning to dialysis after kidney graft loss (GL) is associated with a high risk of mortality, mainly in the first 3–6 months. The follow-up of patients with GL should be extended to better understand crude patient outcomes, mainly in emerging countries, where the transplantation activity has increased.

Methods

This is a historical single-center cohort study conducted in an emerging country (Brazil) that included 115 transplant patients with kidney allograft failure who were followed for 44.1 (21.4; 72.6) months after GL. The outcomes were death or retransplantation after GL calculated by Kaplan-Meier and log-rank tests. Proportional hazard ratios for death and retransplantation were assessed by Cox regression.

Results

The 5-year probability of retransplantation was 38.7% (95% CI: 26.1%-51.2%) and that of death was 37.7% (95% CI: 24.9%-50.5%); OR = 1.03 (95% CI: 0.71–1.70) and P = 0.66. The likelihood of retransplantation was higher in patients who resumed dialysis with higher levels of hemoglobin (HR = 1.22; 95% CI = 1.04–1.43; P = 0.01) and lower in blood type O patients (HR = 0.48; 95% CI = 0.25–0.93; P = 0.03), which was associated with a lower frequency of retransplantation with a subsequent living-donor kidney. On the other hand, the risk of death was significantly associated with Charlson comorbidity index (HR for each point = 1.37; 95% CI 1.19–1.50; P<0.001), and residual eGFR at the time when patients had resumed to dialysis (HR for each mL = 1.14; 95% CI = 1.05–1.25; P = 0.002). The trend toward a lower risk of death when patients had resumed to dialysis using AV fistula access was observed (HR = 0.50; 95% CI 0.25–1.02; P = 0.06), while a higher risk seems to be associated with the number of previous engraftment (HR = 2.01; 95% CI 0.99–4.07; P = 0.05).

Conclusions

The 5-year probability of retransplantation was not less than that of death. Variables related to the probability of retransplantation were hemoglobin level before resuming dialysis and ABO blood type, while the risk of death was associated with comorbidities and residual eGFR.

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.

Association of graft survival with tacrolimus exposure and late intra-patient tacrolimus variability in pediatric and young adult renal transplant recipients-an international CTS registry analysis

Adolescent and young adult age is a high-risk window with an alarmingly increased likelihood of premature kidney graft loss due to immunological rejection. Using the large database of the Collaborative Transplant Study, we analyzed whether a more intense and less variable exposure to tacrolimus could counteract this young age-related enhanced immunoreactivity. Kidney graft recipients aged 12-23 years (n = 964) with a 1-year tacrolimus trough level between 4.0 and 10.9 ng/ml had a 5-year graft survival rate of 85.1%, significantly better than the poor 66.1% rate in patients with a trough level below 4.0 ng/ml who showed a 2.38-fold increased risk of graft loss in the multivariable analysis (P < 0.001). This association was not apparent in young children aged 0-11 years (n = 455) and less pronounced in adults aged 24-34 years (n = 1466). However, an intra-patient variability of tacrolimus (IPV) trough level ≥1.5 at post-transplant years 1 and 2 was associated with an increased graft loss risk in both 12- to 23-year-old and 0- to 11-year-old recipients (P < 0.001 and P = 0.045). Patients with high IPV made up as many as 30% of kidney graft recipients, indicating that a more intense and less variable exposure to tacrolimus could improve graft survival strongly in this high-risk group.

Accuracy and concordance of measurement methods to assess non-adherence after renal transplantation - a prospective study

Background

Non-adherence (NA) to immunosuppressants (IS) among renal transplant recipients (RTRs) is associated with higher risk of allograft rejection, graft loss, and mortality. A precise measurement of NA is indispensable, although its prevalence differs greatly depending on the respective measurement methods. The objective of this study was to assess the accuracy and concordance of different measurement methods of NA in patients after renal transplantation.

Design and methods

This was a single-center prospective observational study. At baseline (T0), NA was measured via physicians’ estimates (PE), self-reports (SR), and tacrolimus trough level variability (CV%) in 78 RTRs. A Visual Analogue Scale (VAS, 0–100%) was applied both for SR and PE. In addition, we used BAASIS© for SR and a 5-point Likert scale for PE. NA was measured prospectively via electronic monitoring (EM, VAICA©) during a three month period. Meanwhile, all participants received phone calls in a two week interval (T1-T6) during which SRs were given.

Results

Seventy-eight RTRs participated in our study. At t0, NA rates of 6.4%, 28.6%, and 15.4% were found for PE, SR, and CV%, respectively. No correlation was found between these methods. During the study, the percentages of self-reported and electronically monitored adherence remained high, with a minimum mean of 91.2% for the strictest adherence measure (Timing Adherence ±30 min). Our results revealed a moderate to high association between SR and EM. In contrast to PE and CV%, SR significantly predicted electronically monitored adherence. Overall, a decreasing effect of electronically monitored adherence was found for both taking and timing adherence (±2 h, ±30 min) over the course of the study.

Discussion

The moderate to high concordance of SR and EM suggests that both methods measure NA equally accurately. SR seems to be a method that can adequately depict electronically monitored NA and may represent a good and economical instrument to assess NA in clinical practice. The increased adherence at the beginning of the study and its subsequent decrease suggests an intervention effect. Surveillance of IS intake via EM with intermittent phone calls could improve adherence on a short-term basis. To establish long-term effects, further research is necessary.