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

Extreme phenotype sampling and next generation sequencing to identify genetic variants associated with tacrolimus in African American kidney transplant recipients

African American (AA) kidney transplant recipients (KTRs) have poor outcomes, which may in-part be due to tacrolimus (TAC) sub-optimal immunosuppression. We previously determined the common genetic regulators of TAC pharmacokinetics in AAs which were CYP3A5 *3, *6, and *7. To identify low-frequency variants that impact TAC pharmacokinetics, we used extreme phenotype sampling and compared individuals with extreme high (n = 58) and low (n = 60) TAC troughs (N = 515 AA KTRs). Targeted next generation sequencing was conducted in these two groups. Median TAC troughs in the high group were 7.7 ng/ml compared with 6.3 ng/ml in the low group, despite lower daily doses of 5 versus 12 mg, respectively. Of 34,542 identified variants across 99 genes, 1406 variants were suggestively associated with TAC troughs in univariate models (p-value < 0.05), however none were significant after multiple testing correction. We suggest future studies investigate additional sources of TAC pharmacokinetic variability such as drug-drug-gene interactions and pharmacomicrobiome.

Nonadherence to Immunosuppressant Therapy of Kidney Transplant Candidate Patients: External Validation of the KATITA-25 Scale

BACKGROUND

The self-administered Kidney AlloTransplant Immunosuppressive Therapy Adherence (KATITA-25) questionnaire is a multidimensional scale for use in the pretransplant setting that evaluates the predisposition to nonadherence of patients who are candidates to kidney transplant. The scale has shown adequate internal consistency and test-retest reliability. This study presents the results of an external validation study of the KATITA-25 scale.

METHODS

Patients >18 y old scheduled for kidney transplant were included in this multicenter study. The KATITA-25 scale was administered before surgery and then at 3-mo posttransplantation for evaluation of scale sensitivity to change. At this time, 2 validated medication adherence scales were applied for assessment of concurrent validity. For evaluation of predictive validity, nonadherence to immunosuppressive medication was assessed at 6 and 12 mo after transplantation by 3 independent methods: patient self-report of nonadherence using the Morisky-Green-Levine Medication Assessment Questionnaire scale, serum trough levels of immunosuppressants, and pharmacy refills.

RESULTS

Three twenty-two patients were available for evaluation of concurrent validity and 311 patients of predictive validity. After kidney transplant, the median KATITA-25 score decreased from 20 to 8 ( P  < 0.001), demonstrating scale sensitivity to change, and the KATITA-25 score showed correlation with the Basel Assessment of Adherence to Immunosuppressive Medication Scale score (Spearman's ρ 0.18, P  = 0.002) and the Cuestionario para la Evaluación de la Adhesión al Tratamiento Antiretroviral scores (ρ -0.17, P  = 0.002), confirming concurrent validity. The nonadherence rate was 57.6%. The scale predictive validity was demonstrated by the area under the receiver operating characteristics curve (0.68), sensitivity (59.8%), specificity (68.2%), and positive predictive value (71.8%).

CONCLUSIONS

This external validation study of KATITA-25 scale provided evidence of sensitivity to change, and structural, criterion, and predictive validity.

Impact of intra-patient variability of tacrolimus on allograft function and CD4 + /CD8 + ratio in kidney transplant recipients: a retrospective single-center study

BACKGROUND

Tacrolimus is a critical component of immunosuppressive therapy for kidney transplant recipients. Intra-patient variation (IPV) of tacrolimus levels affects the function of transplanted kidney.

AIM

This study aimed to investigate the impact of tacrolimus IPV on kidney function, examine its association with post-transplant duration, and assess its effect on the immune status of transplant recipients.

METHOD

This retrospective study was conducted from January 2016 to February 2022. IPV was evaluated using the coefficient of variation (CV) of tacrolimus trough levels from 6 to 48 months after transplantation. Patients were divided into low- and high-IPV groups based on the median CV. Significant differences in kidney function, CD4 + /CD8 + ratio, and post-transplant duration between these groups were analyzed.

RESULTS

Among 189 patients, tacrolimus IPV showed a strong correlation with serum creatinine clearance rate (Ccr) and estimated glomerular filtration rate (eGFR) (p < 0.05). Tacrolimus IPV was significantly correlated with post-transplant duration in only two patients (p < 0.05). Using a median CV of 15.4% to categorize patients, the high IPV group, compared to the low IPV group, exhibited significantly higher eGFR at 6-9 months (p < 0.05), lower Ccr at 9-12 months (p < 0.05), and reduced Ccr and eGFR at 15-18 months (p < 0.05). Six months after transplantation, the high IPV group had a significantly lower CD4 + /CD8 + ratio than the low IPV group (p < 0.05).

CONCLUSION

This study highlights the significant impact of tacrolimus IPV on transplant kidney function and immune status in transplant patients at various post-transplantation intervals.

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.

Extreme Phenotype Sampling and Next Generation Sequencing to Identify Genetic Variants Associated with Tacrolimus in African American Kidney Transplant Recipients

African American (AA) kidney transplant recipients (KTRs) have poor outcomes, which may in-part be due to tacrolimus (TAC) sub-optimal immunosuppression. We previously determined the common genetic regulators of TAC pharmacokinetics in AAs which were CYP3A5 *3, *6, and *7. To identify low-frequency variants that impact TAC pharmacokinetics, we used extreme phenotype sampling and compared individuals with extreme high (n=58) and low (n=60) TAC troughs (N=515 AA KTRs). Targeted next generation sequencing was conducted in these two groups. Median TAC troughs in the high group were 7.7 ng/ml compared with 6.3 ng/ml in the low group, despite lower daily doses of 5 versus 12mg, respectively. Of 34,542 identified variants across 99 genes, 1,406 variants were suggestively associated with TAC troughs in univariate models (p-value <0.05), however none were significant after multiple testing correction. We suggest future studies investigate additional sources of TAC pharmacokinetic variability such as drug-drug-gene interactions and pharmacomicrobiome.

Effect of Tacrolimus Time in Therapeutic Range on Postoperative Recurrence in Patients Undergoing Liver Transplantation for Liver Cancer

BACKGROUND AND OBJECTIVE

Liver cancer is the second highest cause of cancer-related deaths worldwide. It is commonly treated with liver transplantation, where tacrolimus is typically used as an antirejection immunosuppressant. The purpose of this study was to evaluate the effect of tacrolimus time in therapeutic range (TTR) on liver cancer recurrence in liver transplant recipients and to compare the performance of TTRs calculated according to the target ranges recommended in published guidelines.

METHODS

A total of 84 patients who underwent liver transplantation for liver cancer were retrospectively included. Tacrolimus TTR was calculated using linear interpolation from the date of transplantation until recurrence or the last follow-up according to target ranges recommended in the Chinese guideline and international expert consensus.

RESULT

Twenty-four recipients developed liver cancer recurrence after liver transplantation. The CTTR (TTR calculated according to the Chinese guideline) for the recurrence group was significantly lower than that of the nonrecurrence group (26.39% vs. 50.27%, P < 0.001), whereas the ITTR (TTR calculated according to the international consensus) was not significantly different between the two groups (47.81% vs. 56.37%, P = 0.165). Multivariate survival analysis revealed that age, microvascular invasion, hepatocellular carcinoma, CTTR, and mean tacrolimus trough concentration were independent predictors of liver cancer recurrence after liver transplantation.

CONCLUSIONS

TTR predicts liver cancer recurrence in liver transplant recipients. The range of tacrolimus concentrations recommended in the Chinese guideline was more beneficial than that recommended in the international consensus for Chinese patients undergoing liver transplantation for liver cancer.

Comparison of a novel tablet formulation of tacrolimus and conventional capsule formulation in de novo kidney transplant recipients: a systematic review and meta-analysis

Background: The work aimed to compare the pharmacokinetic (PK) profiles and other outcomes reported in observational studies in de novo kidney transplant recipients (KTRs) receiving novel once-daily extended-release tablet tacrolimus (LCPT; LCP-tacrolimus; Envarsus XR) or receiving standard-of-care capsule tacrolimus (PR-Tac; prolonged-release tacrolimus; Advagraf/IR-Tac; immediate-release tacrolimus; Prograf). Methods: A systematic review was conducted for all randomized controlled trials (RCTs) and cohort studies investigating the outcomes in KTRs receiving LCPT or PR-Tac/IR-Tac. We systematically searched PubMed, Web of Science, and EMBASE, with no language restriction. The registered trials and references listed in relevant studies were also searched. Data were extracted for the PK profile, tacrolimus trough level (TTL), and changes in the estimated glomerular filtration rate (eGFR) and serum creatinine (Scr), biopsy-proven acute rejection (BPAR) rate, delayed graft function (DGF) rate, post-transplant diabetes mellitus (PTDM) rate, tremor rate (TR), death rate (DR), and rate of infection by cytomegalovirus (CMV). This study was registered with PROSPERO (registration number: CRD42023403787). Results: A total of seven eligible articles including 1,428 patients with 712 in the LCPT group versus 716 in the PR-Tac/IR-Tac group were included in this study for evidence synthesis. The baseline characteristics of the LCPT, PR-Tac, and IR-Tac groups were similar. The pooled analysis showed a higher PK profile in the LCPT group, and this result was consistent with those of all the included studies. In addition, no significant difference was observed for other outcomes. Conclusion: Considering heterogeneity between studies and potential bias, care providers should select agents based on patient-specific factors and their clinical experience for the immunosuppressive treatment of de novo KTRs.

A prospective controlled, randomized clinical trial of kidney transplant recipients developed personalized tacrolimus dosing using model-based Bayesian Prediction

For three decades, tacrolimus (Tac) dose adjustment in clinical practice has been calculated empirically according to the manufacturer's labeling based on a patient's body weight. Here, we developed and validated a Population pharmacokinetic (PPK) model including pharmacogenetics (cluster CYP3A4/CYP3A5), age, and hematocrit. Our study aimed to assess the clinical applicability of this PPK model in the achievement of Tac Co (therapeutic trough Tac concentration) compared to the manufacturer's labelling dosage. A prospective two-arm, randomized, clinical trial was conducted to determine Tac starting and subsequent dose adjustments in 90 kidney transplant recipients. Patients were randomized to a control group with Tac adjustment according to the manufacturer's labeling or the PPK group adjusted to reach target Co (6-10 ng/ml) after the first steady state (primary endpoint) using a Bayesian prediction model (NONMEM). A significantly higher percentage of patients from the PPK group (54.8%) compared with the control group (20.8%) achieved the therapeutic target fulfilling 30% of the established superiority margin defined. Patients receiving PPK showed significantly less intra-patient variability compared to the control group, reached the Tac Co target sooner (5 days vs 10 days), and required significantly fewer Tac dose modifications compared to the control group within 90 days following kidney transplant. No statistically significant differences occurred in clinical outcomes. Thus, PPK-based Tac dosing offers significant superiority for starting Tac prescription over classical labeling-based dosing according to the body weight, which may optimize Tac-based therapy in the first days following transplantation.

Impact of tacrolimus intra-patient variability in adverse outcomes after organ transplantation

Tacrolimus (Tac) is currently the most common calcineurin-inhibitor employed in solid organ transplantation. High intra-patient variability (IPV) of Tac (Tac IPV) has been associated with an increased risk of immune-mediated rejection and poor outcomes after kidney transplantation. Few data are available concerning the impact of high Tac IPV in non-kidney transplants. However, even in kidney transplantation, there is still a controversy whether high Tac IPV is indeed detrimental in respect to graft and/or patient survival. This may be due to different methods employed to evaluate IPV and distinct time frames adopted to assess graft and patient survival in those reports published up to now in the literature. Little is also known about the influence of high Tac IPV in the development of other untoward adverse events, update of the current knowledge regarding the impact of Tac IPV in different outcomes following kidney, liver, heart, lung, and pancreas tran splantation to better evaluate its use in clinical practice.

Association Between Opioid Dose Reduction Rates and Overdose Among Patients Prescribed Long-Term Opioid Therapy

BACKGROUND

Tapering long-term opioid therapy is an increasingly common practice, yet rapid opioid dose reductions may increase the risk of overdose. The objective of this study was to compare overdose risk following opioid dose reduction rates of ≤10%, 11% to 20%, 21% to 30%, and >30% per month to stable dosing.

METHODS

We conducted a retrospective cohort study in three health systems in Colorado and Wisconsin. Participants were patients ≥18 years of age prescribed long-term opioid therapy between January 1, 2006, and June 30, 2019. Five opioid dosing patterns and drug overdoses (fatal and nonfatal) were identified using electronic health records, pharmacy records, and the National Death Index. Cox proportional hazard regression was conducted on a propensity score-weighted cohort to estimate adjusted hazard ratios (aHRs) for follow-up periods of 1, 3, 6, 9, and 12 months after a dose reduction.

RESULTS

In a cohort of 17 540 patients receiving long-term opioid therapy, 42.7% of patients experienced a dose reduction. Relative to stable dosing, a dose reduction rate of >30% was associated with an increased risk of overdose and the aHR estimates decreased as the follow-up increased; the aHRs for the 1-, 6- and 12-month follow-ups were 5.33 (95% CI, 1.98-14.34), 1.81 (95% CI,1.08-3.03), and 1.49 (95% CI, 0.97-2.27), respectively. The slower tapering rates were not associated with overdose risk.

CONCLUSIONS

Patients receiving long-term opioid therapy exposed to dose reduction rates of >30% per month had increased overdose risk relative to patients exposed to stable dosing. Results support the use of slow dose reductions to minimize the risk of overdose.

Influences of intratumoral heterogeneity on assessment of tumor microenvironment in esophageal squamous cell carcinoma

The intratumoral heterogeneity (ITH) of the tumor microenvironment (TME) has yet to be addressed in esophageal squamous cell carcinoma (ESCC). Here, we studied the ITH of CD8 and PD-L1 status in ESCC, and examined the potential of the tumor surface for representing the TME. In total, 67 surgically resected clinical Stage II ESCC specimens were analyzed. The CD8-cell density, PD-L1 tumor proportion score (TPS), and combined positive score (CPS) were calculated in three (superficial, middle, and deep) areas of each specimen. ITH was quantified by distance-standardized coefficient variations of the three values. The CD8 and PD-L1 status of each area was dichotomized and tumor-surface capabilities for predicting the entire tumor status were estimated. Variables were compared according to the presence of neoadjuvant chemotherapy (NAC). The ITH, especially PD-L1 heterogeneity, differed markedly among specimens. The concordance rates of CD8 and PD-L1 (CPS and TPS) status among the three different areas were 71.6%, 74.6%, and 73.1%, respectively. The sensitivity and the specificity of the tumor surface for predicting the CD8 status of the whole tumor were high, especially in the NAC- group (both 1.0). The tumor surface also showed high capabilities for representing the whole PD-L1 status, while yielding moderate positive predictive values (0.70). The ITH degrees and predictive capabilities did not differ according to NAC. Taken together, the ITH of CD8 and PD-L1 differed among ESCC specimens, while not being markedly affected by NAC. The use of a biopsy specimen from the tumor surface might be feasible for TME evaluation.

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.

Adherence in transplantation

PURPOSE OF REVIEW

Adequately managing a complex medical regimen is paramount to the success of organ transplants. When patients stray from their prescribed medical regimen posttransplant, graft rejection, and death can occur. Predictors of adherence have been studied for many years, and various factors have been identified as contributing to adequate or poor adherence. Both demographic and personal characteristics have been associated with adherence behavior. However, recent developments, such as the COVID-19 pandemic, increased use of mobile health interventions, and use of medical biomarkers have affected the way adherence is measured and applied.

RECENT FINDINGS

The COVID-19 pandemic affected patients' comfort with accessing outpatient care and created a wider use of telehealth services. Measurement of adherence through serum lab levels continues to be reviewed as a potential objective assessment of adherence. Psychosocial factors continue to be identified as major contributors to nonadherence.

SUMMARY

Adherence to antirejection medication, lab work, appointments, and exercise and dietary instructions remains critical to the health of the transplant patient. It is critical that providers involved in the selection process and posttransplant treatment of these patients remain well informed of potential new factors affecting adherence.

Interventions for increasing immunosuppressant medication adherence in solid organ transplant recipients

BACKGROUND

Non-adherence to immunosuppressant therapy is a significant concern following a solid organ transplant, given its association with graft failure. Adherence to immunosuppressant therapy is a modifiable patient behaviour, and different approaches to increasing adherence have emerged, including multi-component interventions. There has been limited exploration of the effectiveness of interventions to increase adherence to immunosuppressant therapy.

OBJECTIVES

This review aimed to look at the benefits and harms of using interventions for increasing adherence to immunosuppressant therapies in solid organ transplant recipients, including adults and children with a heart, lung, kidney, liver and pancreas transplant.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 14 October 2021 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register were identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

All randomised controlled trials (RCTs), quasi-RCTs, and cluster RCTs examining interventions to increase immunosuppressant adherence following a solid organ transplant (heart, lung, kidney, liver, pancreas) were included. There were no restrictions on language or publication type.

DATA COLLECTION AND ANALYSIS

Two authors independently screened titles and abstracts of identified records, evaluated study quality and assessed the quality of the evidence using the GRADE approach. The risk of bias was assessed using the Cochrane tool. The ABC taxonomy for measuring medication adherence provided the analysis framework, and the primary outcomes were immunosuppressant medication initiation, implementation (taking adherence, dosing adherence, timing adherence, drug holidays) and persistence. Secondary outcomes were surrogate markers of adherence, including self-reported adherence, trough concentration levels of immunosuppressant medication, acute graft rejection, graft loss, death, hospital readmission and health-related quality of life (HRQoL). Meta-analysis was conducted where possible, and narrative synthesis was carried out for the remainder of the results.

MAIN RESULTS

Forty studies involving 3896 randomised participants (3718 adults and 178 adolescents) were included. Studies were heterogeneous in terms of the type of intervention and outcomes assessed. The majority of studies (80%) were conducted in kidney transplant recipients. Two studies examined paediatric solid organ transplant recipients. The risk of bias was generally high or unclear, leading to lower certainty in the results. Initiation of immunosuppression was not measured by the included studies. There is uncertain evidence of an association between immunosuppressant medication adherence interventions and the proportion of participants classified as adherent to taking immunosuppressant medication (4 studies, 445 participants: RR 1.09, 95% CI 0.95 to 1.20; I² = 78%). There was very marked heterogeneity in treatment effects between the four studies evaluating taking adherence, which may have been due to the different types of interventions used. There was evidence of increasing dosing adherence in the intervention group (8 studies, 713 participants: RR 1.14, 95% CI 1.03 to 1.26, I² = 61%).  There was very marked heterogeneity in treatment effects between the eight studies evaluating dosing adherence, which may have been due to the different types of interventions used. It was uncertain if an intervention to increase immunosuppressant adherence had an effect on timing adherence or drug holidays. There was limited evidence that an intervention to increase immunosuppressant adherence had an effect on persistence. There was limited evidence that an intervention to increase immunosuppressant adherence had an effect on secondary outcomes. For self-reported adherence, it is uncertain whether an intervention to increase adherence to immunosuppressant medication increases the proportion of participants classified as medically adherent to immunosuppressant therapy (9 studies, 755 participants: RR 1.21, 95% CI 0.99 to 1.49; I² = 74%; very low certainty evidence). Similarly, it is uncertain whether an intervention to increase adherence to immunosuppressant medication increases the mean adherence score on self-reported adherence measures (5 studies, 471 participants: SMD 0.65, 95% CI -0.31 to 1.60; I² = 96%; very low certainty evidence). For immunosuppressant trough concentration levels, it is uncertain whether an intervention to increase adherence to immunosuppressant medication increases the proportion of participants who reach target immunosuppressant trough concentration levels (4 studies, 348 participants: RR 0.98, 95% CI 0.68 to 1.40; I² = 40%; very low certainty evidence). It is uncertain whether an intervention to increase adherence to immunosuppressant medication may reduce hospitalisations (5 studies, 460 participants: RR 0.67, 95% CI 0.44 to 1.02; I² = 64%; low certainty evidence). There were limited, low certainty effects on patient-reported health outcomes such as HRQoL. There was no clear evidence to determine the effect of interventions on secondary outcomes, including acute graft rejection, graft loss and death. No harms from intervention participation were reported.

AUTHORS' CONCLUSIONS

Interventions to increase taking and dosing adherence to immunosuppressant therapy may be effective; however, our findings suggest that current evidence in support of interventions to increase adherence to immunosuppressant therapy is overall of low methodological quality, attributable to small sample sizes, and heterogeneity identified for the types of interventions. Twenty-four studies are currently ongoing or awaiting assessment (3248 proposed participants); therefore, it is possible that findings may change with the inclusion of these large ongoing studies in future updates.

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.

Adherence to immunosuppression in adult heart transplant recipients: A systematic review

BACKGROUND

Successful maintenance of a heart transplant (HTx) graft requires adherence to a triple-drug regimen of immunosuppression. However, achieving adequate adherence can be difficult secondary to complicated dosing regimens, side effects, and mental/emotional barriers. A detailed review of current patterns of adherence to immunosuppression in adult HTx recipients is lacking.

OBJECTIVE

This systematic review aims to detail the current landscape of adherence to immunosuppression in adult heart transplant patients, including the measurement of adherence, correlates to adherence, health outcomes associated with nonadherence, as well as strategies to improve adherence in HTx patients.

METHODS

We conducted searches in PubMed MEDLINE, Embase, CENTRAL register of Controlled Trials (Wiley), and Scopus, from inception to March 2020. Studies were eligible if they outlined an aspect of adherence (as noted above in the objective) to immunosuppression in adult HTx patients. The HTx cohort had to contain at least 10 patients and measurement of adherence had to be done with an objective or otherwise validated measure of adherence (e.g. drug levels, automated pill bottles or adherence questionnaires). Two authors independently screened the articles for inclusion, then subsequently reviewed the full texts of the included articles. Data was extracted into standardized forms and bias evaluations were done using the Newcastle-Ottawa or modified Newcastle-Ottawa tools, depending on the study type. The authors followed all guidelines for the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

RESULTS

The titles/abstracts of 880 articles were reviewed. Ultimately, 23 articles were included in the final review. The median number of participants was 101, with a range of 19 to 1397. Studies provided information on baseline levels of adherence (17 studies), correlates to adherence (14 studies), health outcomes related to nonadherence (3 studies) and interventions to improve adherence (3 studies). Baseline adherence estimates varied greatly depending on the adherence measure. Multiple significant correlates to nonadherence exist and appear to affect patients with certain sociodemographic backgrounds, those with psychological/psychiatric comorbidities and those with poor support structures. Nonadherence is associated with transplant coronary artery disease and acute late rejection; it may also be associated with long-term mortality. Finally, a simplified dosing regimen with once-a-day tacrolimus as well as use of a mobile phone-based intervention were associated with improved adherence. Bias scores were most deficient due to self-reported outcomes in 18 studies, and lack of controls/adjustments for confounders, in 7 studies.

CONCLUSIONS

Adherence to immunosuppression in transplant patients varies, but is associated with observable and modifiable factors which are worth addressing. Further high-quality studies regarding strategies to improve adherence are needed in the literature.