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

Model-informed precision dosing: State of the art and future perspectives

Model-informed precision dosing (MIPD) stands as a significant development in personalized medicine to tailor drug dosing to individual patient characteristics. MIPD moves beyond traditional therapeutic drug monitoring (TDM) by integrating mathematical predictions of dosing, and considering patient-specific factors (patient characteristics, drug measurements) as well as different sources of variability. For this purpose, rigorous model qualification is required for the application of MIPD in patients. This review delves into new methods in model selection and validation, also highlighting the role of machine learning in improving MIPD, the utilization of biosensors for real-time monitoring, as well as the potential of models integrating biomarkers for efficacy or toxicity for precision dosing. The clinical evidence of TDM and MIPD is discussed for various medical fields including infection medicine, oncology, transplant medicine, and inflammatory bowel diseases, thereby underscoring the role of pharmacokinetics/pharmacodynamics and specific biomarkers. Further research, particularly randomized clinical trials, is warranted to corroborate the value of MIPD in enhancing patient outcomes and advancing personalized medicine.

Evaluating the evidence for genotype-informed Bayesian dosing of tacrolimus in children undergoing solid organ transplantation: A systematic literature review

Tacrolimus, a calcineurin inhibitor, is a highly effective immunosuppressant used in solid organ transplantation (SOT). However, it is characterized by a narrow therapeutic range and high inter-patient variability in pharmacokinetics. Standard weight-based dosing followed by empiric dose titration is suboptimal in controlling drug concentrations, increasing risk of rejection or toxicity, particularly in the initial months post transplantation. This review explores the potential of combined pre-transplant genotyping and pharmacokinetic (PK) modelling to improve tacrolimus dosing in paediatric SOT recipients. A systematic search of Medline, Embase and Cochrane databases identified studies published between March 2013 and March 2023 that investigated genotype- and PK model-informed tacrolimus dosing in children post-SOT. The Newcastle-Ottawa Scale assessed study quality. Seven studies encompassing paediatric kidney, heart, liver and lung transplants reported using genotype and model-informed dosing. A combination of clinical and genetic factors significantly impacts tacrolimus clearance and thus initial dose recommendation. Body size, transplant organ and co-medications were consistently important, while either time post-transplant or haematocrit emerged in some studies. Several models were identified, however, with limitations evident in some and with absence of evidence for their effectiveness in optimizing initial and subsequent dosing. This review highlights the development of PK models in paediatric SOT that integrate genotype and clinical covariates to personalize early tacrolimus dosing. While promising, prospective studies are needed to validate and confirm their effectiveness in improving time to therapeutic concentrations and reducing under- or overexposure. This approach has the potential to optimize tacrolimus therapy in paediatric SOT, thereby improving outcomes.

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.

Steroid-tacrolimus drug-drug interaction and the effect of CYP3A genotypes

AIMS

Tacrolimus, metabolized by CYP3A4 and CYP3A5 enzymes, is susceptible to drug-drug interactions (DDI). Steroids induce CYP3A genes to increase tacrolimus clearance, but the effect is variable. We hypothesized that the extent of the steroid-tacrolimus DDI differs by CYP3A4/5 genotypes.

METHODS

Kidney transplant recipients (n = 2462) were classified by the number of loss of function alleles (LOF) (CYP3A5*3, *6 and *7 and CYP3A4*22) and steroid use at each tacrolimus trough in the first 6 months post-transplant. A population pharmacokinetic analysis was performed by nonlinear mixed-effect modelling (NONMEM) and stepwise covariate modelling to define significant covariates affecting tacrolimus clearance. A stochastic simulation was performed and translated into a Shiny application with the mrgsolve and Shiny packages in R.

RESULTS

Steroids were associated with modestly higher (3%-11.8%) tacrolimus clearance. Patients with 0-LOF alleles receiving steroids showed the greatest increase (11.8%) in clearance compared to no steroids, whereas those with 2-LOFs had a negligible increase (2.6%) in the presence of steroids. Steroid use increased tacrolimus clearance by 5% and 10.3% in patients with 1-LOF and 3/4-LOFs, respectively.

CONCLUSIONS

Steroids increase the clearance of tacrolimus but vary slightly by CYP3A genotype. This is important in individuals of African ancestry who are more likely to carry no LOF alleles, may more commonly receive steroid treatment, and will need higher tacrolimus doses.

Study protocol for the development and validation of a questionnaire evaluating predisposition to immunosuppressant medication non-adherence of kidney pre-transplant patients. The KATITA project

Non-adherence to immunosuppressive medication after kidney transplant is an important cause of graft rejection and loss. Approaches to minimization of non-adherence have focused on the identification of episodes of medication non-adherence, but by then irreparable harm to the graft may already have occurred, and a more effective approach would be to adopt preventive measures in patients who may have difficulty in adhering to medication. The aim of this study protocol is to develop and validate a clinical questionnaire for assessing, in kidney transplant candidate patients in the pre-transplant setting, the predisposition to non-adherence to immunosuppressive medication. In this multicenter, prospective study, a pilot questionnaire in Brazilian Portuguese language, composed of Likert-scaled statements expressing patients' beliefs, behaviors and barriers regarding medication taking will be assembled from a literature review, from focus groups, and an expert panel. The pilot questionnaire will be administered to a minimum of 300 patients in kidney transplant waiting lists and exploratory factor analysis will be used for development of the definitive questionnaire. A random subsample of a minimum of 60 patients will have the scale re-administered after one month for evaluation of test-retest reliability. A multicenter, external validation study will include 364 kidney transplant candidates who will be evaluated immediately before surgery and at months 3, 6 and 12 post-transplant for assessment of concurrent validity, by comparison with two scales that assess medication non-adherence, and for determination of predictive validity using a triangulation method for assessment of medication non-adherence. Structural validity will be assessed with confirmatory factor analysis using structural equation modeling. Cross-cultural generalizability and validity will be assessed by a multicenter study, in which a translation of the scale to another language will be administered to kidney transplant candidate patients from a different culture, with a subsample being selected for test-retest. This study will be conducted in Spain with a Spanish translation of the scale.

Using Prior Knowledge on Systems Through PBPK to Gain Further Insight into Routine Clinical Data on Trough Concentrations: The Case of Tacrolimus in Chronic Kidney Disease

BACKGROUND

Routine therapeutic drug monitoring (TDM) relies heavily on measuring trough drug concentrations. Trough concentrations are affected not only by drug bioavailability and clearance, but also by various patient and disease factors and the volume of distribution. This often makes interpreting differences in drug exposure from trough data challenging. This study aimed to combine the advantages of top-down analysis of therapeutic drug monitoring data with bottom-up physiologically-based pharmacokinetic (PBPK) modeling to investigate the effect of declining renal function in chronic kidney disease (CKD) on the nonrenal intrinsic metabolic clearance ( CLint ) of tacrolimus as a case example.

METHODS

Data on biochemistry, demographics, and kidney function, along with 1167 tacrolimus trough concentrations for 40 renal transplant patients, were collected from the Salford Royal Hospital's database. A reduced PBPK model was developed to estimate CLint for each patient. Personalized unbound fractions, blood-to-plasma ratios, and drug affinities for various tissues were used as priors to estimate the apparent volume of distribution. Kidney function based on the estimated glomerular filtration rate ( eGFR ) was assessed as a covariate for CLint using the stochastic approximation of expectation and maximization method.

RESULTS

At baseline, the median (interquartile range) eGFR was 45 (34.5-55.5) mL/min/1.73 m 2 . A significant but weak correlation was observed between tacrolimus CLint and eGFR (r = 0.2, P < 0.001). The CLint declined gradually (up to 36%) with CKD progression. Tacrolimus CLint did not differ significantly between stable and failing transplant patients.

CONCLUSIONS

Kidney function deterioration in CKD can affect nonrenal CLint for drugs that undergo extensive hepatic metabolism, such as tacrolimus, with critical implications in clinical practice. This study demonstrates the advantages of combining prior system information (via PBPK) to investigate covariate effects in sparse real-world datasets.

A prospective validation of a population pharmacokinetic model of tacrolimus in Tunisian kidney transplant patients

BACKGROUND

A prospective validation of pharmacokinetic population (Pk pop) of Tacrolimus (Tac) for dose adjustment in kidney transplant patients was assessed in only one study. The present study was aimed at prospectively evaluating the performance of our previously developed Tac- Pk pop model in predicting trough concentration (C0) in Tunisian kidney transplant patients.

PATIENTS AND METHOD

It was a prospective study including patients who had undergone kidney transplantation at Monastir-Nephrology Department. The population study was divided into adherence and control groups.

RESULTS

A total of 198 C0 (30 patients) were analyzed. The proportion of C0 within TR was 63.9% and 38.0% in the adhesion and control group, respectively. The percentage of C0 within TR was significantly higher in the adherence group during both early and late post-transplant period (p = 0.03 and 0.04, respectively). This percentage was found to be significantly higher during the third C0 monitoring and thereafter in the adherence group compared with the control group (65.8% vs 41%, respectively).

CONCLUSION

Tac dose proposal based on this model could be helpful to improve clinical outcomes in our population by reducing the risk of acute rejection and this immunosuppressant's toxic side effects.

The Importance Of Avoiding Time-Dependent Bias When Testing The Prognostic Value Of An Intervening Event - Two Acute Cellular Rejection Examples In Intestinal Transplantation

In testing the prognostic value of the occurrence of an intervening event (clinical event that occurs post-transplant), 3 proper statistical methodologies for testing its prognostic value exist (time dependent covariate, landmark, and semi-Markov modelling methods). However, time-dependent bias has appeared in many clinical reports, whereby the intervening event is statistically treated as a baseline variable (as if it occurred at transplant). Using a single-center cohort of 445 intestinal transplant cases to test the prognostic value of 1^st acute cellular rejection (ACR) and severe (grade of) ACR on the hazard rate of developing graft loss, we demonstrate how the inclusion of such time-dependent bias can lead to severe underestimation of the true hazard ratio (HR). The (statistically more powerful) time dependent covariate method in Cox's multivariable model yielded significantly unfavorable effects of 1^st ACR (P<.0001; HR=2.492) and severe ACR (P<.0001; HR=4.531). In contrast, when using the time-dependent biased approach, multivariable analysis yielded an incorrect conclusion for the prognostic value of 1^st ACR (P=.31, HR=0.877, 35.2% of 2.492) and a much smaller estimated effect of severe ACR (P=.0008; HR=1.589; 35.1% of 4.531). In conclusion, this study demonstrates the importance of avoiding time-dependent bias when testing the prognostic value of an intervening event.

Tacrolimus CYP3A Single-Nucleotide Polymorphisms and Preformed T- and B-Cell Alloimmune Memory Improve Current Pretransplant Rejection-Risk Stratification in Kidney Transplantation

Achieving fast immunosuppression blood exposure after kidney transplantation is key to abrogating both preformed and de novo anti-donor humoral and cellular alloresponses. However, while tacrolimus (TAC) is the cornerstone immunosuppressant inhibiting adaptive alloimmunity, its blood exposure is directly impacted by different single-nucleotide polymorphisms (SNPs) in CYP3A TAC-metabolizing enzymes. Here, we investigated how functional TAC-CYP3A genetic variants (CYP3A4*22/CYP3A5*3) influence the main baseline clinical and immunological risk factors of biopsy-proven acute rejection (BPAR) by means of preformed donor-specific antibodies (DSAs) and donor-specific alloreactive T cells (DSTs) in a large European cohort of 447 kidney transplants receiving TAC-based immunosuppression. A total of 70 (15.7%) patients developed BPAR. Preformed DSAs and DSTs were observed in 12 (2.7%) and 227 (50.8%) patients, respectively. According to the different CYP3A4*22 and CYP3A5*3 functional allele variants, we found 4 differential new clusters impacting fasting TAC exposure after transplantation; 7 (1.6%) were classified as high metabolizers 1 (HM1), 71 (15.9%) as HM2, 324 (72.5%) as intermediate (IM), and 45 (10.1%) as poor metabolizers (PM1). HM1/2 showed significantly lower TAC trough levels and higher dose requirements than IM and PM (p < 0.001) and more frequently showed TAC underexposure (<5 ng/ml). Multivariate Cox regression analyses revealed that CYP3A HM1 and IM pharmacogenetic phenotypes (hazard ratio (HR) 12.566, 95% CI 1.99–79.36, p = 0.007, and HR 4.532, 95% CI 1.10–18.60, p = 0.036, respectively), preformed DSTs (HR 3.482, 95% CI 1.99–6.08, p < 0.001), DSAs (HR 4.421, 95% CI 1.63–11.98, p = 0.003), and delayed graft function (DGF) (HR 2.023, 95% CI 1.22–3.36, p = 0.006) independently predicted BPAR. Notably, a significant interaction between T-cell depletion and TAC underexposure was observed, showing a reduction of the BPAR risk (HR 0.264, 95% CI 0.08–0.92, p = 0.037). Such variables except for DSAs displayed a higher predictive risk for the development of T cell-mediated rejection (TCMR). Refinement of pretransplant monitoring by incorporating TAC CYP3A SNPs with preformed DSAs as well as DSTs may improve current rejection-risk stratification and help induction treatment decision-making.

Development of De Novo Donor-specific HLA Antibodies and AMR in Renal Transplant Patients Depends on CYP3A5 Genotype

BACKGROUND

The single-nucleotide polymorphism CYP3A5 rs776746 is related to a reduction in the metabolizing activity of the CYP3A5 enzyme. People carrying at least one copy of the wild-type allele, defined as CYP3A5 expressers, exhibit higher clearance and lower trough concentrations of tacrolimus than homozygous nonexpressers, and this difference may affect alloimmunization and allograft function.

METHODS

We retrospectively studied 400 kidney transplant recipients treated with a tacrolimus-based immunosuppression regimen to detect CYP3A5 genotype, de novo formation of HLA antibodies and donor-specific antibodies (DSAs), and clinical outcome up to 5 y after transplant.

RESULTS

We found that 69 (17%) of the 400 patients were CYP3A5 expressers. During the first 3 y after transplant, CYP3A5 expressers tended to have lower tacrolimus trough levels than nonexpressers, although their tacrolimus dosage was as much as 80% higher. De novo DSAs were found more frequently in CYP3A5 expressers than in nonexpressers (13/69 [19%] versus 33/331 [10%], P = 0.02). De novo DSA-free survival rates (P = 0.02) were significantly lower for expressers than for nonexpressers. CYP3A5 genotype had no effect on allograft failure, but CYP3A5 expressers exhibited a significantly higher frequency of antibody-mediated rejection. CYP3A5 expresser status was an independent risk factor for the development of de novo DSAs (relative risk, 2.34, P = 0.01).

CONCLUSIONS

Early detection of CYP3A5 expressers, enabling genotype-based dose adjustment of tacrolimus immediately after renal transplant, may be a useful strategy for reducing the risk of de novo DSA production and antibody-mediated rejection.

EBV, CMV, and BK viral infections in pediatric kidney transplantation: Frequency, risk factors, treatment, and outcomes

BACKGROUND

Improved short- and long-term outcomes of kidney transplantation have been achieved over the past decades due to improved immunosuppression. This may have increased the risk for infections and, particularly, for the viral infections: cytomegalovirus (CMV), Epstein-Barr virus (EBV), and polyoma BK virus (BKV).

METHODS

A retrospective review of viremic CMV, EBV, and BKV infections in pediatric renal transplant recipients treated and followed by a national referral center over a 10-year period.

RESULTS

Sixty-seven patients (68% males) received 68 kidney grafts (62% from living donors) during the study period; the mean follow-up period was 5.2 ± 2.4 years. Twenty-seven viremic episodes were documented (CMV: 13, EBV: 6, BKV: 8) in 24 patients (35.2%). The median time (interquartile range) to viremia post-transplant was 11 (4-38) months. The viral infection rate was significantly higher in the years 2014-2015 than in previous years (61% vs. 29%, p = .017). Compared to patients who did not develop viremia, patients with viremias were younger at the time of transplantation, were more likely to receive thymoglobulin induction pre-transplant and to develop an acute rejection. Multiple logistic regression modeling identified transplant year and recipient's age as significant risk factors for viremia. Graft outcome and eGFR at the last follow-up was similar between patients who did and did not develop viremia.

CONCLUSIONS

Viral infections continue to be a major cause of morbidity in pediatric kidney transplant recipients. However, with close monitoring and prompt intervention, patient and renal outcomes remain favorable.

Effect of drug combination on tacrolimus target dose in renal transplant patients with different CYP3A5 genotypes

Various factors, including genetic polymorphisms, drug-drug interactions, and patient characteristics influence the blood concentrations of tacrolimus in renal transplant patients. In the present study, we established a population pharmacokinetic model to explore the effect of combined use of Wuzhi capsules/echinocandins and the patients' biochemical parameters such as hematocrit on blood concentrations and target doses of tacrolimus in renal transplant patients with different CYP3A5 genotypes. The aim of the study was to propose an individualized tacrolimus administration regimen for early renal transplant recipients.In this retrospective cohort study, we included 240 renal transplant recipients within 21 days of surgery (174 males and 66 females, mean age 39.4 years), who received tacrolimus alone (n = 54), in combination with Wuzhi capsules (99) or caspofungin (57) or micafungin (30). We collected demographic characteristics, clinical indicators, CYP3A5 genotypes, and 1950 steady-state trough concentrations of tacrolimus and included them in population pharmacokinetic model. An additional 110 renal transplant recipients and 625 steady-state trough concentrations of tacrolimus were included for external validation of the model. The population pharmacokinetic model was established and Monte Carlo was used to simulate probabilities for achieving the target concentration for individual tacrolimus administration.A two-compartment model of first-order absorption and elimination was developed to describe the population pharmacokinetics of tacrolimus. CYP3A5 genotypes and co-administration of Wuzhi capsules, as well as time after renal transplantation and hematocrit, were important factors affecting the clearance of tacrolimus. We found no obvious change in trend in the scatter plot of tacrolimus clearance rate vs. hematocrit. The Monte Carlo simulation indicated the following recommended doses of tacrolimus alone: 0.14 mg·kg^-1·d^-1 for genotype CYP3A5*1*1, 0.12 mg·kg^-1·d^-1 for CYP3A5*1*3, and 0.10 mg·kg^-1·d^-1 for CYP3A5*3*3. For patients receiving the combination with Wuzhi capsules, the recommended doses of tacrolimus were 0.10 mg·kg^-1·d^-1 for CYP3A5*1*1, 0.08 mg·kg^-1·d^-1 for CYP3A5*1*3, and 0.06 mg·kg^-1·d^-1 for CYP3A5*3*3 genotypes. Caspofungin or micafungin had no effect on the clearance of tacrolimus in renal transplant recipients.The population pharmacokinetics of tacrolimus in renal transplant patients was evaluated and the individual administration regimen of tacrolimus was simulated. For early kidney transplant recipients receiving tacrolimus treatment, not only body weight, but also CYP3A5 genotypes and drugs used in combination should be considered when determining the target dose of tacrolimus.

Early Monitoring and Subsequent Gain of Tacrolimus Time-In-Therapeutic Range May Improve Clinical Outcomes After Living Kidney Transplantation

BACKGROUND

The early identification of recipients at high risk of graft loss is clinically relevant after kidney transplantation. The authors explored whether the earlier monitoring of tacrolimus (Tac) time-in-therapeutic range (TTR) is predictive of and a subsequent gain in TTR improves transplant outcomes.

METHODS

The TTR within 3, 6, 9, and 12 months was evaluated. Multivariate Cox analyses were performed to explore when TTR was predictive of transplant outcomes. Patients were divided into 3 groups based on incremental TTR change [TTR gain (increase >10%), TTR stable (maintained within 10%), and TTR loss (decrease >10%)] and 4 groups based on predefined cutoff values [low-low (LL), low-high (LH), high-low (HL), and high-high (HH)] using 6- and 12-month TTRs. Death-censored graft loss and patient death were primary outcomes.

RESULTS

Nonlinear associations were observed between 6-, 9-, and 12-month TTR and death-censored graft and patient survival rates. In multivariate analysis, every 10% increase in 6-, 9-, and 12-month TTRs was associated with reduced patient death [hazard ratio (HR): 0.83; HR: 0.68; HR: 0.61, respectively] and graft loss (HR: 0.88; HR: 0.73; HR: 0.66, respectively). A nonlinear relationship was observed between transplant outcomes and incremental changes in TTR. TTR gain and stable TTR contributed to higher graft survival (HR: 0.20; HR: 0.21) and patient survival (HR: 0.14; HR: 0.15) rates than TTR loss, whereas the former 2 had comparable outcomes. Furthermore, compared with those in the HH group, the LL and HL groups had inferior graft survival (HR: 3.33; HR: 5.17) and patient survival (HR: 5.15; HR: 8.94) rates, whereas the LH group had similar outcomes (P = 0.63, P = 0.97). Nonadherence was the main controllable risk factor for low TTR.

CONCLUSIONS

The 6-month TTR identified patients at higher risk of worse outcomes. The subsequent gain of TTR may contribute to better transplant outcomes.

Tacrolimus Bayesian Dose Adjustment in Pediatric Renal Transplant Recipients

BACKGROUND

Immunosuppressant Bayesian Dose Adjustment (ISBA) is an online expert system that estimates the area under the curve (AUC) of immunosuppressive drugs through pharmacokinetic modelling and Bayesian estimation to propose dose adjustments to reach predefined exposure targets. The ISBA database was retrospectively analyzed to describe tacrolimus pharmacokinetics and exposure, evaluate the efficiency of ISBA dose recommendations, and propose tacrolimus AUC0-12h target ranges for pediatric renal allograft recipients treated with immediate release tacrolimus.

METHODS

The database included 1935 tacrolimus dose adjustment requests from 419 patients <19 years old who were treated with immediate-release tacrolimus and followed in 21 French hospitals. The tacrolimus exposure evolution with patient age and posttransplantation time, the correlation between trough tacrolimus concentration (C0) and AUC0-12h at different periods posttransplantation, and the efficiency of dose recommendations to avoid underexposure and overexposure and to decrease between-patient AUC variability were investigated.

RESULTS

Tacrolimus AUC showed large between-patient variability (CV% = 40%) but moderate within-patient variability (median = 24.3% over a 3-month period). Dose-standardized exposure but not the AUC/C0 ratio significantly decreased with time posttransplantation and patient age. We derived AUC0-12h ranges from the consensual C0 ranges using linear regression equations. When the ISBA recommended dose was applied, the AUC distribution was narrower and a significantly higher proportion was within the targets (P < 0.0001).

CONCLUSIONS

ISBA efficiently reduced tacrolimus underexposure and overexposure. The AUC0-12h target ranges for pediatric patients derived from the database were similar to those previously reported for adults. Estimating the AUC/C0 ratio could help determine personalized C0 targets.

Clinical Rationale for a Routine Testing Schedule Using Donor-Derived Cell-Free DNA After Kidney Transplantation

Kidney transplant recipients require meticulous clinical and laboratory surveillance to monitor allograft health. Conventional biomarkers, including serum creatinine and proteinuria, are lagging indicators of allograft injury, often rising only after significant and potentially irreversible damage has occurred. Immunosuppressive medication levels can be followed, but their utility is largely limited to guiding dosing changes or assessing adherence. Kidney biopsy, the criterion standard for the diagnosis and characterization of injury, is invasive and thus poorly suited for frequent surveillance.

Donor-derived cell-free DNA (dd-cfDNA) is a sensitive, noninvasive, leading indicator of allograft injury, which offers the opportunity for expedited intervention and can improve long-term allograft outcomes. This article describes the clinical rationale for a routine testing schedule utilizing dd-cfDNA surveillance at months 1, 2, 3, 4, 6, 9, and 12 during the first year following kidney transplantation and quarterly thereafter. These time points coincide with major immunologic transition points after transplantation and provide clinicians with molecular information to help inform decision making.

Tacrolimus time-in-therapeutic range is associated with freedom from acute rejection and graft failure following intestinal transplantation

BACKGROUND

Trough-adjusted tacrolimus is commonly prescribed following intestinal transplantation to prevent allograft rejection. Despite established practice, there remains limited direct evidence linking tacrolimus levels with improved clinical outcomes.

METHODS

This was a single-center review of all adult non-liver containing intestinal allograft recipients from 2011 to 2018. Patients received lymphocyte depleting induction and maintenance immunosuppression consisting of tacrolimus and a corticosteroid taper. Tacrolimus time-in-therapeutic range (TAC-TTR) was calculated for all patients from the date of transplant until 1-year post-transplant using Rosendaal's method. Cox-Proportional hazards modeling was utilized to assess freedom from acute rejection and graft failure stratified by TAC-TTR quartile.

RESULTS

47 patients were included in the review. Mean TAC-TTR for the cohort was 30.2% ± 11.4. Fifteen episodes of acute rejection were observed, 8 of which were severe. Patients in the highest TAC-TTR quartile >36% had a lower incidence of acute rejection and graft failure relative to patients with a TAC-TTR <20%. Cox-Proportional hazards modeling found a 10% decrease in TAC-TTR was associated with an increased hazard for acute rejection (2.03), severe acute rejection (2.19), and graft loss (3.33).

CONCLUSION

The results of this study suggest that decreasing TAC-TTR is a risk factor for both acute rejection as well as intestinal allograft failure.

BK Polyomavirus Nephropathy in Kidney Transplantation: Balancing Rejection and Infection

BK polyomavirus nephropathy (BKVN) and allograft rejection are two closely-associated diseases on opposite ends of the immune scale in kidney transplant recipients. The principle of balancing the immune system remains the mainstay of therapeutic strategy. While patient outcomes can be improved through screening, risk factors identification, and rapid reduction of immunosuppressants, a lack of standard curative therapy is the primary concern during clinical practice. Additionally, difficulty in pathological differential diagnosis and clinicopathology’s dissociation pose problems for a definite diagnosis. This article discusses the delicate evaluation needed to optimize immunosuppression and reviews recent advances in molecular diagnosis and immunological therapy for BKVN patients. New biomarkers for BKVN diagnosis are under development. For example, measurement of virus-specific T cell level may play a role in steering immunosuppressants. The development of cellular therapy may provide prevention, even a cure, for BKVN, a complex post-transplant complication.

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.

Clinical Pharmacokinetics and Bayesian Estimators for the Individual Dose Adjustment of a Generic Formulation of Tacrolimus in Adult Kidney Transplant Recipients

BACKGROUND

Tacrolimus has a narrow therapeutic range and requires dose adjustment, usually based on the trough blood concentration but preferably on the area under the concentration-time curve over 12 h post-dose (AUC_0-12h). The single-arm, multicentre, clinical study IMPAKT aimed: (i) to develop, in de novo kidney transplant recipients, pharmacokinetic models and maximum a-posteriori Bayesian estimators for a generic, immediate-release, oral formulation of tacrolimus to estimate tacrolimus AUC_0-12h at different post-transplant periods using a limited sampling strategy, and considering the CYP3A5*3 polymorphism as a covariate and (ii) to compare the performance of these Bayesian estimators to those previously developed for the original formulation.

METHODS

Thirty patients were enrolled and 29 provided nine blood samples over 9 h at day 7 and months 1 and 3 post-transplant. Tacrolimus blood profiles measured with liquid chromatography-tandem mass spectrometry were modelled using one-compartment, double gamma absorption, linear elimination models developed in-house. Different limited sampling strategies of three time-points within 4 h post-dose were tested for the maximum a-posteriori Bayesian estimator of tacrolimus AUC_0-12h. The models and estimators were validated internally and their performance compared to that of models previously developed for the original formulation.

RESULTS

The concentration-time curves, AUC_0-12h/dose and trough blood concentration/dose exhibited wide inter-individual variability. The covariate-free pharmacokinetic models developed for the three post-transplant periods closely fitted the individual profiles. Maximum a-posteriori Bayesian estimators based on three different limited sampling strategies and no covariate yielded accurate AUC_0-12h estimates, including for the five cytochrome P450 3A5 expressers and for the four patients without corticosteroids. The 0-1 h-3 h strategy finally chosen had very low bias (- 4.0 to - 2.5%) and imprecision (root mean square error 5.5-9.2%). The maximum a-posteriori Bayesian estimators previously developed for the reference product fitted the generic profiles with similar performance.

CONCLUSIONS

We developed original pharmacokinetic models and accurate maximum a-posteriori Bayesian estimators to estimate patient exposure and adjust the dose of generic tacrolimus, and confirmed that the robust tools previously developed for the original formulation can be applied to this generic.

Body weight-based initial dosing of tacrolimus in renal transplantation: Is this an ideal approach?

BACKGROUND

Tacrolimus dosing immediately posttransplant is based on body weight. Recent studies have highlighted that the dosing of tacrolimus purely based on weight may not be appropriate, particularly in individuals who are obese.

OBJECTIVES

This study aimed to estimate the effect of body mass index (BMI) and the weight-based dosing on tacrolimus trough levels in recipients of renal transplants.

DESIGN AND PARTICIPANTS

This study was conducted on 400 of the 863 patients registered in the Salford, UK, renal transplant database between 2012 and 2019 who had complete and analysable datasets. Data were collected at baseline (first tacrolimus trough level after transplantation), after 1 month and 6 months posttransplantation. The cohort was split into three groups based on BMI (kg/m² ; Group 1 ≤ 25, Group 2 > 25-30 and Group 3 > 30) which were compared with respect to tacrolimus dose, plasma levels and concentration/dose (C/D) ratio at the three-time points.

RESULTS

Patients in the higher BMI group (Group 3) had significantly higher baseline tacrolimus trough levels despite receiving a lower initiation dose per kilogram of body weight. After 1 and 6-months posttransplant, the higher BMI group were receiving a significantly lower tacrolimus dose relative to their body weight, with a significant negative correlation between body weight and tacrolimus/kg body weight. There was no adverse relationship evident between tacrolimus dosing or concentration and graft function.

CONCLUSIONS

Our study showed that standard dosing of tacrolimus based on body weight in individuals who were obese did not adversely affect their tacrolimus concentrations or transplant function.

Maintenance Immunosuppression in Solid Organ Transplantation: Integrating Novel Pharmacodynamic Biomarkers to Inform Calcineurin Inhibitor Dose Selection

Calcineurin inhibitors, the primary immunosuppressive therapy used to prevent alloreactivity of transplanted organs, have a narrow therapeutic index. Currently, treatment is individualized based on clinical assessment of the risk of rejection or toxicity guided by trough concentration monitoring. Advances in immune monitoring have identified potential markers that may have value in understanding calcineurin inhibitor pharmacodynamics. Integration of these markers has the potential to complement therapeutic drug monitoring. Existing pharmacokinetic-pharmacodynamic (PK-PD) data is largely limited to correlation between the biomarker and trough concentrations at single time points. Immune related gene expression currently has the most evidence supporting PK-PD integration. Novel biomarker-based approaches to pharmacodynamic monitoring including development of enhanced PK-PD models are proposed to realize the full clinical benefit.

Evaluation of Tacrolimus Trough Level in Patients Who Developed Post-transplant Diabetes Mellitus After Kidney Transplantation: A Retrospective Single-Center Study in Saudi Arabia

BACKGROUND

Post-transplant diabetes mellitus (PTDM) is a complication after kidney transplantation. Studies showed an association between high trough levels of tacrolimus FK506 and PTDM. This study aims to investigate the association between FK506 trough levels during the first year after kidney transplant and the incidence of PTDM.

METHODS

This retrospective study included adult kidney transplant patients who were not diabetic before transplantation from 2011 to 2014. The analysis evaluated FK506 trough levels at different time points post-transplant, as well as other variables to determine whether they were associated with PTDM.

RESULTS

The cumulative incidence of PTDM was 22.5% with a median time to PTDM diagnosis of 10 months. PTDM patients had higher first FK506 (ng/mL) levels (P = .001), and more patients in the PTDM group had FK506 level >10 ng/mL during the first 3 months (P = .004). After 12 months of transplant, PTDM patients had higher body mass index (BMI) 28.3 ± 6.9 kg/m² compared to non-PTDM patients 26.4 ± 6.7 kg/m² (P = .015). Binary logistic regression analysis showed that age ≥40 years (odds ratio [OR] = 2.75, P = .004), BMI ≥25 kg/m² (OR = 2.04, P = .040), and FK506 level ≥10 ng/mL during the first 3 months (OR = 2.65, P = .009) were significantly related to PTDM development.

CONCLUSION

Patients with FK506 trough level >10 ng/mL during the first 3 months after transplantation are at higher risk of PTDM, especially in patients >40 years of age and/or who are overweight. These results may strengthen the notion that there is a connection between high FK506 trough levels and PTDM development.

Tacrolimus trough levels higher than 6 ng/mL might not be required after a year in stable kidney transplant recipients

Background

Little is known regarding optimal tacrolimus (TAC) trough levels after 1 year post-transplant in stable kidney transplant recipients (KTRs) who have not experienced renal or cardiovascular outcomes. This study aimed to investigate the effect of 1-year post-transplant TAC trough levels on long-term renal and cardiovascular outcomes and opportunistic infections in stable KTRs.

Methods

KTRs receiving TAC with mycophenolate-based immunosuppression who did not experience renal or cardiovascular outcomes within 1 year post-transplant were enrolled from a multicenter observational cohort study. Renal outcome was defined as a composite of biopsy-proven acute rejection, interstitial fibrosis and tubular atrophy, and death-censored graft loss. Cardiovascular outcome was defined as a composite of de novo cardiomegaly, left ventricular hypertrophy, and cardiovascular events. Opportunistic infections were defined as the occurrence of BK virus or cytomegalovirus infections.

Results

A total of 603 eligible KTRs were divided into the low-level TAC (LL-TAC) and high-level TAC (HL-TAC) groups based on a median TAC level of 5.9 ng/mL (range 1.3–14.3) at 1 year post-transplant. The HL-TAC group had significantly higher TAC trough levels at 2, 3, 4, and 5 years compared with the levels of the LL-TAC group. During the mean follow-up of 63.7 ± 13.0 months, there were 121 renal outcomes and 224 cardiovascular outcomes. In multivariate Cox regression analysis, LL-TAC and HL-TAC were not independent risk factors for renal and cardiovascular outcomes, respectively. No significant differences in the development of opportunistic infections and de novo donor-specific anti-human leukocyte antigen antibodies and renal allograft function were observed between the two groups.

Conclusions

TAC trough levels after 1 year post-transplant remained at a similar level until the fifth year after kidney transplantation and were not directly associated with long-term outcomes in stable Korean KTRs who did not experience renal or cardiovascular outcomes. Therefore, in Asian KTRs with a stable clinical course, TAC trough levels higher than approximately 6 ng/mL might not be required after a year of kidney transplantation.

Tacrolimus Trough Level at the First Month May Predict Renal Transplantation Outcomes Among Living Chinese Kidney Transplant Patients: A Propensity Score-Matched Analysis

Supplemental Digital Content is Available in the Text.

Background:

Monitoring and maintaining a stable tacrolimus trough level is essential because of its narrow therapeutic window and considerable fluctuation in the early phase after kidney transplantation. However, optimal tacrolimus exposure early after transplantation remains unclear among Chinese patients.

Methods:

In this propensity score–matched cohort study, we thoroughly investigated the association between tacrolimus trough level at the first month and acute rejection (AR) as well as infection within the first year after kidney transplantation.

Results:

In a first step, a total of 1415 patients were divided into 3 groups according to the receiver operating characteristic curve: low-level group (410 patients with a tacrolimus trough level <5.35 ng/mL at the first month), median-level group (466 patients with a tacrolimus trough level from 5.35 to 7.15 ng/mL), and high-level group (539 patients with a tacrolimus trough level >7.15 ng/mL). Ultimately, 363 and 459 pairs of cases were enrolled by using 2 propensity score matches between low- and median-level groups and between high- and median-level groups, respectively. Compared with patients in the low-level group, patients in the median-level group had lower risk of AR without increased incidence of infection (AR, 12.4% versus 5.7%, P = 0.02; infection, 13.2% versus 13.2%, P = 1.00 for low- and median-level groups, respectively) within the first year. Compared with patients in the high-level group, patients in the median-level group had lower incidence of infection without the growing risk of AR (infection, 17.6% versus 12.2%, P = 0.021; AR, 4.6% versus 5.4%, P = 0.545 for high- and median-level groups, respectively) within the first year. Multilogistic analysis showed that tacrolimus trough levels were an independent factor for AR (odds ratio, 0.749, 95% confidence interval, 0.632–0.888, P = 0.001). Tacrolimus trough levels were also associated with infection (odds ratio 1.110, 95% confidence interval, 1.013–1.218, P = 0.001). Serum creatinine levels were similar among groups. No difference was found in 1-, 3-, and 5-year graft survival and patient survival among groups.

Conclusions:

The tacrolimus trough level maintained between 5.35 and 7.15 ng/mL at the first posttransplant month may prevent AR without increasing the incidence of infection within the first year after living kidney transplantation among Chinese patients.

The Many Faces of Calcineurin Inhibitor Toxicity-What the FK?

Calcineurin inhibitors (CNIs) are both the savior and Achilles' heel of kidney transplantation. Although CNIs have significantly reduced rates of acute rejection, their numerous toxicities can plague kidney transplant recipients. By 10 years, virtually all allografts will have evidence of CNI nephrotoxicity. CNIs have been strongly associated with hypertension, dyslipidemia, and new onset of diabetes after transplantation-significantly contributing to cardiovascular risk in the kidney transplant recipient. Multiple electrolyte derangements including hyperkalemia, hypomagnesemia, hypercalciuria, metabolic acidosis, and hyperuricemia may be challenging to manage for the clinician. Finally, CNI-associated tremor, gingival hyperplasia, and defects in hair growth can have a significant impact on the transplant recipient's quality of life. In this review, the authors briefly discuss the pharmacokinetics of CNI and discuss the numerous clinically relevant toxicities of commonly used CNIs, cyclosporine and tacrolimus.

Changes in the commercial brand of tacrolimus lead to subtherapeutic trough levels and acute rejection in renal transplant recipients

BACKGROUND

The vigilance of tacrolimus (TAC) trough levels is an essential part of renal transplant follow up. Reduced TAC trough levels and high variability are related to adverse outcomes. The aim of this study was to evaluate the impact of brand changes on tacrolimus (TAC) subtherapeutic (SubT) trough levels, acute rejection (AR), and kidney function.

METHODS

This is a prospective, observational cohort study of renal transplant recipients, between January 2016 and October 2018. Tacrolimus trough levels and brand used by the patient were both registered at every consult. Tacrolimus values ≤3.5 ng/mL were considered SubT.

RESULTS

445 patients were included. The median number of TAC brand changes was 2 (IQR, 1-4). Patients were grouped according to the number of brand changes: Group 1 = 0 (n = 107), Group 2 = 1-4 (n = 236), and Group 3 = ≥5 (n = 102). Patients with the greatest number of brand changes had a greater proportion and number of SubT TAC trough levels (Group 1 = 36.4%, average 0.53; Group 2 = 39.8%, average 0.65, Group 3 = 59.8%, average 1.17, P < .001) and AR (Group 1 = 0.9%, Group 2 = 11%, Group 3 = 14.7%, P < .001). On multivariate analysis, SubT levels and the number of brand changes were related to AR.

CONCLUSIONS

In Mexico, changes in TAC brand are associated with an elevated frequency of SubT levels. Brand changes and SubT levels are independently associated with acute rejection. The supply policies on TAC brands in Mexico require revision to avoid changing brands as much as possible.

Optimizing Mycophenolic Acid Exposure in Kidney Transplant Recipients: Time for Target Concentration Intervention

The immunosuppressive agent mycophenolate is used extensively in kidney transplantation, yet dosing strategy applied varies markedly from fixed dosing ("one-dose-fits-all"), to mycophenolic acid (MPA) trough concentration monitoring, to dose optimization to an MPA exposure target (as area under the concentration-time curve [MPA AUC0-12]). This relates in part to inconsistent results in prospective trials of concentration-controlled dosing (CCD). In this review, the totality of evidence supporting mycophenolate CCD is examined: pharmacological characteristics, observational data linking exposure to efficacy and toxicities, and randomized controlled trials of CCD, with attention to dose optimization method and exposure achieved. Fixed dosing of mycophenolate consistently leads to underexposure associated with rejection, as well as overexposure associated with toxicities. When CCD is driven by pharmacokinetic calculation to a target concentration (target concentration intervention), MPA exposure is successfully controlled and clinical benefits are seen. There remains a need for consensus on practical aspects of mycophenolate target concentration intervention in contemporary tacrolimus-containing regimens and future research to define maintenance phase exposure targets. However, given ongoing consequences of both overimmunosuppression and underimmunosuppression in kidney transplantation, impacting short- and long-term outcomes, these should be a priority. The imprecise "one-dose-fits-all" approach should be replaced by the clinically proven MPA target concentration strategy.

Long-term Clinical Significance of Tacrolimus Trough Level at the Early Period After Kidney Transplantation

BACKGROUND

The stable immunosuppressant level at the early period after kidney transplantation (KT) is one of the most important factors for the prognosis of KT. However, the extent of immunosuppression varies according to the policies of each KT center. We investigated the relationship between the clinical outcome and tacrolimus trough level (TTL) at the early post-transplant period.

MATERIALS AND METHODS

We retrospectively analyzed medical records of patients who underwent KT between July 2007 and June 2016. We investigated TTLs at 3 months after KT. We evaluated the incidence of biopsy-proven acute rejection (BPAR), cytomegalovirus infection, and graft survival according to the TTLs.

RESULTS

A total of 426 patients who received KT during the study period were enrolled. The mean age of KT recipients was 46.3 ± 11.5 years, and 55.5% of patients were men. The incidence of BPAR within 1 year after KT was significantly higher when TTLs at 3 months were less than 4.0 ng/mL (P = .020). Death-censored graft survival rates were significantly lower in KT recipients with BPAR and TTL less than 4.0 ng/mL (P < .001, P < .001, respectively). In multivariate analysis, BPAR and TTL less than 4.0 ng/mL at 3 months after KT were independent risk factors for graft failure.

CONCLUSION

BPAR and TTL less than 4.0 ng/mL at 3 months after KT are important risk factors for allograft failure. Therefore, TTL should be kept at least 4.0 ng/mL or more at 3 months after KT to reduce the incidence of BPAR within 1 year after KT.

Comparison of the effects of standard vs low-dose prolonged-release tacrolimus with or without ACEi/ARB on the histology and function of renal allografts

Targeting the renin-angiotensin system and optimizing tacrolimus exposure are both postulated to improve outcomes in renal transplant recipients (RTRs) by preventing interstitial fibrosis/tubular atrophy (IF/TA). In this multicenter, prospective, open-label controlled trial, adult de novo RTRs were randomized in a 2 × 2 design to low- vs standard-dose (LOW vs STD) prolonged-release tacrolimus and to angiotensin-converting enzyme inhibitors/angiotensin II receptor 1 blockers (ACEi/ARBs) vs other antihypertensive therapy (OAHT). There were 2 coprimary endpoints: the prevalence of IF/TA at month 6 and at month 24. IF/TA prevalence was similar for LOW vs STD tacrolimus at month 6 (36.8% vs 39.5%; P = .80) and ACEi/ARBs vs OAHT at month 24 (54.8% vs 58.2%; P = .33). IF/TA progression decreased significantly with LOW vs STD tacrolimus at month 24 (mean [SD] change, +0.42 [1.477] vs +1.10 [1.577]; P = .0039). Across the 4 treatment groups, LOW + ACEi/ARB patients exhibited the lowest mean IF/TA change and, compared with LOW + OAHT patients, experienced significantly delayed time to first T cell-mediated rejection. Renal function was stable from month 1 to month 24 in all treatment groups. No unexpected safety findings were detected. Coupled with LOW tacrolimus dosing, ACEi/ARBs appear to reduce IF/TA progression and delay rejection relative to reduced tacrolimus exposure without renin-angiotensin system blockade. ClinicalTrials.gov identifier: NCT00933231.

Comparison of Transplant Outcomes for Low-level and Standard-level Tacrolimus at Different Time Points after Kidney Transplantation

BACKGROUND

Optimal tacrolimus (TAC) trough levels for different periods after kidney transplantation (KT) has not been definitely established. This study aimed to investigate transplant outcomes of low-level (LL) and standard-level (SL) TAC according to post-transplant period.

METHODS

A total of 278 consecutive kidney transplant recipients (KTRs) receiving TAC-based immunosuppression were divided into LL and SL-TAC groups (4-7 and 7-12 ng/mL for 0-2 months, 3-6 and 6-10 ng/mL for 3-6 months, 2-5 and 5-8 ng/mL for 7-12 months, respectively) according to TAC trough level at each period. We compared estimated glomerular filtration rate (eGFR), biopsy-proven acute rejection (BPAR), de novo donor-specific antibody (dnDSA), calcineurin inhibitor (CNI) toxicity, opportunistic infection, and allograft survival.

RESULTS

SL-TAC group showed significantly higher mean eGFR at 0-2 months than LL-TAC group (72.1 ± 20.3 vs. 64.2 ± 22.7 mL/min/1.73m²; P = 0.003). Incidence of BPAR at 7-12 months was significantly lower in SL-TAC group than in LL-TAC group (0.0% vs. 3.9%; P = 0.039). Patients with persistent SL-TAC lasting 12 months showed higher eGFR at 7-12 months than those with persistent LL-TAC (65.5 ± 13.0 vs. 57.9 ± 13.9 mL/min/1.73m²; P = 0.007). No significant differences in dnDSA, CNI toxicity, serious infections, or allograft survival were observed.

CONCLUSIONS

Maintenance of proper TAC trough level after 6 months could reduce BPAR without adverse drug toxicities in KTRs. Moreover, persistent SL-TAC during the first year after KT might have a beneficial effect on a trend for a lower incidence of dnDSA and better renal allograft function.

Low early posttransplant serum tacrolimus levels are associated with poor patient survival in lung transplant patients

BACKGROUND:

Low-dose tacrolimus-based immunosuppression is a standard therapy in kidney and liver transplantation; however, the optimal therapeutic level of tacrolimus has not been established in lung transplantation. We aimed to identify the tacrolimus level associated with better outcomes in lung transplant patients.

METHODS:

This retrospective study included patients who underwent lung transplantation at Seoul National University Hospital between 2006 and 2016. Kaplan–Meier survival analysis and Cox regression were performed according to tacrolimus levels at several time-points within 1-year posttransplantation.

RESULTS:

A total of 43 patients received bilateral lung transplantation. The median age was 53 years and the median follow-up was 20.5 months. Overall and 1-year patient survival rates were 55.8% and 74.4%, respectively. Infection was the most common cause of death (78.9%). Chronic lung allograft dysfunction was observed in 16.3%. A tacrolimus level <9 ng/ml at 1 month was associated with lower rejection-free survival (P = 0.009). A time-averaged tacrolimus level <10 ng/ml within 1 month posttransplantation was an independent risk factor for poor patient survival (hazard ratio: 4.904; 95% confidence interval: 1.930–12.459; P= 0.001). Furthermore, higher tacrolimus levels did not increase infectious complications.

CONCLUSIONS:

These finding suggest that tacrolimus levels ≥10 ng/ml within 1 month after lung transplantation appear to be associated with better patient survival.

Tacrolimus trough and dose intra-patient variability and CYP3A5 genotype: Effects on acute rejection and graft failure in European American and African American kidney transplant recipients

BACKGROUND

Suboptimal immunosuppression after kidney transplantation contributes to toxicity and loss of efficacy. Little is known regarding the impact of intra-patient variability of tacrolimus (TAC) doses and troughs in the early post-transplant period or the influence of genetic variants on variability.

METHODS

Coefficients of variation (CV) of TAC troughs and doses of 1226 European American (EA) and 246 African American (AA) adult recipients enrolled in DeKAF Genomics were compared for association with acute rejection and graft failure. Additionally, the influence of recipients' number of CYP3A5 loss-of-function alleles was assessed.

RESULTS

Acute rejection was associated with greater CV of dose in AA (P < 0.001) and EA recipients (P = 0.012). Graft failure was associated with a greater CV of dose (P = 0.022) and trough (P < 0.001) in AA, and higher CV of trough (P = 0.024) in EA recipients. In EA, CYP3A5 loss-of-function alleles were associated with decreased CV of trough (P = 0.0042) and increased CV of dose (P < 0.0001).

CONCLUSION

CYP3A5 loss-of-function alleles influence intra-patient TAC trough and dose variability. High variability of TAC dose increases risk of acute rejection. High variability of TAC trough increases risk of graft failure. Early clinical recognition of TAC dose and trough variability may improve patient management and outcomes.

Early Immunosuppressive Exposure of Enteric-Coated-Mycophenolate Sodium Plus Tacrolimus Associated with Acute Rejection in Expanded Criteria Donor Kidney Transplantation

Background:

Immunosuppressive agents are still inefficient in preventing biopsy-proven acute rejection (BPAR) after expanded criteria donor (ECD) kidney transplantation. The aim of this study was to investigate the relationships between early immunosuppressive exposure and the development of BPAR.

Methods:

We performed a retrospective study of 58 recipients of ECD kidney transplantation treated with enteric-coated-mycophenolate sodium, tacrolimus (Tac), and prednisone. The levels of mycophenolic acid-area under the curve (MPA-AUC)_0-12h and Tac C₀ were measured at the 1^st week and the 1^st month posttransplant, respectively. The correlation was assessed by multivariate logistic regression.

Results:

The occurrence rates of BPAR and antibody-mediated rejection were 24.1% and 10.3%, respectively. A low level of MPA-AUC_0-12h at the 1^st week posttransplant was found in BPAR recipients (38.42 ± 8.37 vs. 50.64 ± 13.22, P < 0.01). In addition, the incidence of BPAR was significantly high (P < 0.05) when the MPA-AUC_0-12h level was <30 mg·h^-1·L^-1 at the 1^st week (15.0% vs. 44.4%) or the Tac C₀ was <4 ng/ml at the 1^st month posttransplant (33.3% vs. 21.6%). Multivariable logistic regression analysis showed that the MPA-AUC_0-12h at the 1^st week (OR: 0.842, 95% CI: 0.784-0.903) and the Tac C₀ at the 1^st month (OR: 0.904, 95% CI: 0.822–0.986) had significant inverse correlation with BPAR (P < 0.05).

Conclusions:

Low-level exposure of MPA and Tac C₀ in the early weeks posttransplant reflects an increased acute rejection risk, which suggested that MPA-AUC_0-12h <30 mg·h^-1·L^-1 and Tac C₀ <4 ng/ml should be avoided in the first few weeks after transplantation.

Attempted validation of 44 reported SNPs associated with tacrolimus troughs in a cohort of kidney allograft recipients

AIM

Multiple genetic variants have been associated with variation in tacrolimus (TAC) trough concentrations. Unfortunately, additional studies do not confirm these associations, leading one to question if a reported association is accurate and reliable. We attempted to validate 44 published variants associated with TAC trough concentrations.

MATERIALS & METHODS

Genotypes of the variants in our cohort of 1923 kidney allograft recipients were associated with TAC trough concentrations.

RESULTS

Only variants in CYP3A4 and CYP3A5 were significantly associated with variation in TAC trough concentrations in our validation.

CONCLUSION

There is no evidence that common variants outside the CYP3A4 and CYP3A5 loci are associated with variation in TAC trough concentrations. In the future rare variants may be important and identified using DNA sequencing.

Genome-wide association study identifies the common variants in CYP3A4 and CYP3A5 responsible for variation in tacrolimus trough concentration in Caucasian kidney transplant recipients

The immunosuppressant tacrolimus (TAC) is metabolized by both cytochrome P450 3A4 (CYP3A4) and CYP3A5 enzymes. It is common for European Americans (EA) to carry two CYP3A5 loss-of-function (LoF) variants that profoundly reduces TAC metabolism. Despite having two LoF alleles, there is still considerable variability in TAC troughs and identifying additional variants in genes outside of the CYP3A5 gene could provide insight into this variability. We analyzed TAC trough concentrations in 1345 adult EA recipients with two CYP3A5 LoF alleles in a genome-wide association study. Only CYP3A4*22 was identified and no additional variants were genome-wide significant. Additional high allele frequency genetic variants with strong genetic effects associated with TAC trough variability are unlikely to be associated with TAC variation in the EA population. These data suggest that low allele frequency variants, identified by DNA sequencing, should be evaluated and may identify additional variants that contribute to TAC pharmacokinetic variability.

A high intrapatient variability in tacrolimus exposure is associated with poor long-term outcome of kidney transplantation

Tacrolimus is a critical dose drug with a considerable intrapatient variability (IPV) in its pharmacokinetics. We investigated whether a high IPV in tacrolimus exposure is associated with adverse long-term renal transplantation outcomes. Tacrolimus IPV was calculated from predose concentrations measured between 6 and 12 months post-transplantation of 808 renal transplant recipients (RTRs) transplanted between 2000 and 2010. One hundred and eighty-eight (23.3%) patients reached the composite end point consisting of graft loss, late biopsy-proven rejection, transplant glomerulopathy, or doubling of serum creatinine concentration between month 12 and the last follow-up. The cumulative incidence of the composite end point was significantly higher in patients with high IPV than in patients with low IPV (hazard ratio: 1.41, 95% CI: 1.06-1.89; P = 0.019). After the adjustment for several factors, the higher incidence of the composite end point for RTRs with a high IPV remained statistically significant (hazard ratio: 1.42, 95% CI: 1.06-1.90; P = 0.019). Younger recipient age at transplantation, previous transplantation, worse graft function (at month 6 post-transplantation), and low mean tacrolimus concentration at 1 year post-transplantation were additional predictors for worse long-term transplant outcome. A high tacrolimus IPV is an independent risk factor for adverse kidney transplant outcomes that can be used as an easy monitoring tool to help identify high-risk RTRs.

Effect of CYP3A5 genotype, steroids, and azoles on tacrolimus in a pediatric renal transplant population

BACKGROUND

Numerous studies have described the impact of cytochrome P450 3A5 (CYP3A5) genotype on Tacrolimus (TAC) exposure. The purpose of this study was to conduct a comprehensive analysis of genetic and non-genetic factors affecting the TAC dose-exposure relationship over the first year post pediatric renal transplant.

METHODS

Data were collected retrospectively for the first year post-transplant in pediatric renal transplant patients receiving TAC maintenance immunosuppression. The effect of CYP3A5 genotype (CYP3A5*3 and *6 alleles), age, azoles, and corticosteroids on TAC trough concentration normalized for dose (TAC Co/D ng/ml/mg/kg/day) was assessed using a linear mixed model.

RESULTS

Over time, TAC Co/D was lower in recipients with CYP3A5*1/*3 genotype compared to those with CYP3A5*3/*3 genotype (44.5 ± 14.4 vs. 107.6 ± 6.4, p = 0.03), increased in patients >12 years of age compared to < 12 years (93.9 ± 8.7 vs. 53.1 ± 12.9, p = 0.007), and decreased by concomitant corticosteroids (69.5 ± 12.7 vs. 89.9 ± 20.0, p = 0.04). The observed increased TAC Co/D in the presence of azoles (271 ± 41 vs. 111 ± 91, p = 0.016) could be attributed to clotrimazole.

CONCLUSIONS

Multiple factors, including CYP3A5 genotype, and age, influence TAC Co/D in pediatric kidney transplant recipients. Clotrimazole administered as troches also contribute to TAC Co/D variability.