The interactions of age, sex, body mass index, genetics, and steroid weight-based doses on tacrolimus dosing requirement after adult kidney transplantation. Eur J Clin Pharmacol. 2012;68:671-680. [PMID: 22101623 DOI: 10.1007/s00228-011-1150-0]

Single Nucleotide Polymorphisms of CYP3A4 and CYP3A5 in Romanian Kidney Transplant Recipients: Effect on Tacrolimus Pharmacokinetics in a Single-Center Experience

Background: This study examines the impact of CYP3A4 and CYP 3A5 genotypes on tacrolimus (Tac) pharmacokinetics in Romanian kidney transplanted patients. Methods: We included 112 kidney recipients genotyped for CYP3A5*3, CYP3A4*1.001, and CYP3A4*22. Patients were categorized into poor, intermediate, rapid, and ultra-rapid metabolizers based on the functional defects linked to CYP3A variants. Results: Predominantly male (63.4%) with an average age of 40.58 years, the cohort exhibited a high prevalence of the CYP3A4*1/*1 (86.6%) and CYP3A5*3/*3 (77.7%) genotypes. CYP3A4*1.001 and CYP3A5*1 alleles significantly influenced the Tac concentration-to-dose (C0/D) ratio in various post-transplant periods, while the CYP3A4*22 allele showed no such effect (p = 0.016, p < 0.001). Stepwise regression highlighted the CYP3A4*1.001's impact in early post-transplant phases, with hematocrit and age also influencing Tac variability. Conclusions: The study indicates a complex interaction of CYP3A4 and CYP3A5 genotypes on Tac metabolism, suggesting the necessity for personalized medication approaches based on genetic profiling in kidney transplant recipients.

Tacrolimus Concentration/Dose Ratio: A Tool for Guiding Tacrolimus Dosage Post-renal Transplantation

Background The calcineurin inhibitor, Tacrolimus (Tac), exhibits variable absorption and undergoes first-pass metabolism when administered orally. The narrow therapeutic window and individual variability of this immunosuppressive agent make therapeutic drug monitoring essential. We hypothesized that the Tac metabolism rate - defined as the blood concentration normalized by its daily dose (the C/D ratio) - is associated with post-renal transplant (RTx) function. Methodology A retrospective observational study was conducted including 40 RTx patients. Clinical reports from four follow-up ambulatory appointments at one, three, six, and 12 months were analyzed. Tac dose and its blood levels were used to calculate the Tac concentration/dose (C/D) ratio. Patients with a Tac C/D ratio <1.05 ng/mL x 1/mg and a C/D ratio >1.05 ng/mL x 1/mg were categorized as fast and slow metabolizers. Serum creatinine levels were compared between the two groups, and their association with the Tac C/D ratio was analyzed. Student's unpaired t-test and the Mann-Whitney U test were used to analyze the difference in the C/D ratio between the groups. Spearman correlation analysis was conducted to analyze the association of the C/D ratio with serum creatinine in both groups. A P-value of <0.05 was considered statistically significant. Results Fast metabolizers showed increased serum creatinine (P < 0.05), and the C/D ratio correlated with creatinine levels. ROC analysis used to identify fast metabolizers for the C/D ratio at three months had an area of 0.925 (P < 0.01). Conclusions The Tac C/D ratio can be used as an earlier diagnostic tool to predict the development of nephrotoxicity in RTx patients.

Retrospective evaluation of LCP-tacrolimus (Envarsus XR) dosing in de novo kidney transplant

INTRODUCTION

Tacrolimus is known to exhibit significant inter- and intra-patient pharmacokinetic (PK) and pharmacodynamic (PD) variability regarding therapeutic response. LCP-tacrolimus (LCPT-Envarsus XR) was approved in 2018 for use as a de novo immunosuppressive agent in kidney transplants, but there is limited evidence to guide de novo dosing of LCPT in patients with obesity. The primary objective of this study was to evaluate the impact of different calculated weight-based de novo LCPT dosing on early transplant outcomes.

METHODS

This was a retrospective study of patients with obesity (BMI ≥ 30 kg/m2 ) who received a kidney transplant at the University of Illinois Hospital and Health System (UIH), between March 2019 and March 2021. Subjects were included if were age 18 years or older and received de novo LCPT throughout index hospitalization. The primary endpoint of this study was to compare correlations between the first tacrolimus trough level and dosing weight strategy (e.g., TBW, AdjBW, IBW).

RESULTS

There was a statistically significant, though modest, correlation between all three dosing strategies and the first tacrolimus trough level (TBW correlation coefficient = .431, p < .001; AdjBW correlation coefficient = .455, p < .001; IBW correlation coefficient = .465; p < .001). In regression modeling for supratherapeutic levels each additional .01 mg/kg increase in dose by TBW, AdjBW, and IBW increased the odds of a supratherapeutic level by 1.46, 1.34, and 1.24, respectively (p < .001).

CONCLUSIONS

The use of LCPT in kidney transplant recipients with obesity dosed using TBW demonstrated the strongest correlation with initial supratherapeutic tacrolimus levels. Larger prospective studies are needed to investigate the further impact of body weight on dosing regimens in the obese population.

Identification of Drugs Acting as Perpetrators in Common Drug Interactions in a Cohort of Geriatric Patients from Southern Italy and Analysis of the Gene Polymorphisms That Affect Their Interacting Potential

BACKGROUND

Pharmacogenomic factors affect the susceptibility to drug-drug interactions (DDI). We identified drug interaction perpetrators among the drugs prescribed to a cohort of 290 older adults and analysed the prevalence of gene polymorphisms that can increase their interacting potential. We also pinpointed clinical decision support systems (CDSSs) that incorporate pharmacogenomic factors in DDI risk evaluation.

METHODS

Perpetrator drugs were identified using the Drug Interactions Flockhart Table, the DRUGBANK website, and the Mayo Clinic Pharmacogenomics Association Table. Allelic variants affecting their activity were identified with the PharmVar, PharmGKB, dbSNP, ensembl and 1000 genome databases.

RESULTS

Amiodarone, amlodipine, atorvastatin, digoxin, esomperazole, omeprazole, pantoprazole, simvastatin and rosuvastatin were perpetrator drugs prescribed to >5% of our patients. Few allelic variants affecting their perpetrator activity showed a prevalence >2% in the European population: CYP3A4/5*22, *1G, *3, CYP2C9*2 and *3, CYP2C19*17 and *2, CYP2D6*4, *41, *5, *10 and *9 and SLC1B1*15 and *5. Few commercial CDSS include pharmacogenomic factors in DDI-risk evaluation and none of them was designed for use in older adults.

CONCLUSIONS

We provided a list of the allelic variants influencing the activity of drug perpetrators in older adults which should be included in pharmacogenomics-oriented CDSSs to be used in geriatric medicine.

EnGraft: a multicentre, open-label, randomised, two-arm, superiority study protocol to assess bioavailability and practicability of Envarsus® versus Advagraf™ in liver transplant recipients

BACKGROUND

Graft rejection and chronic CNI toxicity remain obstacles to organ transplant success. Current formulations of tacrolimus, such as Prograf® and Advagraf™, exhibit limitations in terms of pharmacokinetics and tolerability, related in part to suboptimal bioavailability. As dosing non-compliance can result in graft rejection, the once daily formulation of tacrolimus, Advagraf™, was developed (vs 2x/day Prograf®). Benefits of Advagraf™ are counterbalanced by delayed achievement of therapeutic trough levels and need for up to 50% higher doses to maintain Prograf®-equivalent troughs. Envarsus® is also a prolonged-release once-daily tacrolimus formulation, developed using MeltDose™ drug-delivery technology to increase drug bioavailability; improved bioavailability results in low patient drug absorption variability and less pronounced peak-to-trough fluctuations. In phase III de novo kidney transplant studies, Envarsus® proved non-inferior to twice-daily tacrolimus; however, no phase IV studies show superiority of Envarsus® vs Advagraf™ in de novo liver transplant (LTx) recipients.

METHODS

The EnGraft compares bioavailability and tests superiority of Envarsus® (test arm) versus Advagraf™ (comparator arm) in de novo LTx recipients. A total of 268 patients from 15 German transplant centres will be randomised 1:1 within 14 days post-LTx. The primary endpoint is dose-normalised trough level (C/D ratio) measured 12 weeks after randomisation. Secondary endpoints include the number of dose adjustments, time to reach first defined trough level and incidence of graft rejections. Additionally, clinical and laboratory parameters will be assessed over a 3-year period.

DISCUSSION

C/D ratio is an estimate for tacrolimus bioavailability. Improving bioavailability and increasing C/D ratio using Envarsus could reduce renal dysfunction and other tacrolimus-related toxicities; previous trials have shown that a higher C/D ratio (i.e. slower tacrolimus metabolism) is not only associated with improved renal function but also linked to reduced neurotoxic side effects. A higher C/D ratio could improve clinical outcomes for LTx recipients; EnGraft has begun, with one third of patients recruited by January 2022.

TRIAL REGISTRATION

This trial has been registered (4 May 2020) in the EU Clinical Trials Register, EudraCT-Nummer: 2020-000796-20. Additionally, this trial has been registered (22 January 2021) at ClinicalTrials.gov: NCT04720326. The trial received a favourable opinion from the concerned lead ethics committee at the University of Regensburg, under the reference 20-1842-112.

Intestinal Permeability in Patients Early after Kidney Transplantation Treated with Two Different Formulations of Once-Daily Tacrolimus

Adequate tacrolimus blood exposure is crucial in the early post-renal transplant period and a gut epithelial barrier integrity may play a role. We prospectively investigated several markers of intestinal permeability in recent kidney transplant recipients (KTRs) treated with different tacrolimus extended-release formulations. Within each of the 49 KTR pairs that received grafts from the same donor, an early randomized conversion was performed from twice-daily (Prograf) to once-daily tacrolimus formulation: Advagraf or Envarsus. Plasma zonulin, calprotectin, circulating lipopolysaccharide (LPS), LPS-binding protein (LBP), intestinal fatty acid binding protein (FABP-2), and CD-14 levels were measured. There was no difference in the recipient age, dialysis vintage, BMI, and residual diuresis between Advagraf and Envarsus groups. FABP-2 and LPS levels were significantly associated with tacrolimus trough level, 3-h level, and area under the curve (AUC) in the Envarsus but not in the Advagraf group. AUC was independently increased by LPS and decreased by age, FABP-2 concentration, and the use of Envarsus formulation as compared with Advagraf. Functional changes of gastrointestinal tract in patients treated with Envarsus may influence intestinal tacrolimus absorption to a greater extent than in Advagraf-treated KTRs and may lead to inadequate variability of tacrolimus exposure early after kidney transplantation.

Compare the performance of multiple machine learning models in predicting tacrolimus concentration for infant patients with living donor liver transplantation

BACKGROUND

This study aims to establish multiple ML models and compare their performance in predicting tacrolimus concentration for infant patients who received LDLT within 3 months after transplantation.

METHODS

Retrospectively collected basic information and relevant biochemical indicators of included infant patients. CMIA was used to determine tacrolimus C₀ . PCR was used to determine the donors' and recipients' CYP3A5 genotypes. Multivariate stepwise regression analysis and stepwise elimination covariates were used for covariates selection. Thirteen machine learning algorithms were applied for the development of prediction models. APE, the ratio of the APE ≤3 ng ml^-1 and ideal rate (the proportion of the predicted value with a relative error of 30% or less) were used to evaluate the predictive performance of the model.

RESULTS

A total of 163 infant patients were included in this study. In the case of the optimal combination of covariates, the Ridge model had the lowest APE, 2.01 (0.85, 3.35 ng ml^-1 ). The highest ratio of the APE ≤3 ng ml^-1 was the LAR model (71.77%). And the Ridge model showed the highest ideal rate (55.05%). For the Ridge model, GRWR was the most important predictor.

CONCLUSIONS

Compared with other ML models, the Ridge model had good predictive performance and potential clinical application.

Impact of POR*28 Variant on Tacrolimus Pharmacokinetics in Kidney Transplant Patients with Different CYP3A5 Genotypes

BACKGROUND

The introduction of tacrolimus (TAC) in clinical practice was essential to the establishment of transplantation as therapy for patients with chronic renal disease. However, the higher interindividual variation of TAC metabolism has been an important limiting factor for its clinical use. Although the relationship between CYP3A5 polymorphisms and TAC pharmacokinetics (PK) is well established, the effects of other genetic variants on TAC metabolism, such as POR*28, still remain uncertain.

OBJECTIVE

To evaluate the impact of POR variants on TAC PK in renal transplant patients with different CYP3A5 genotypes (expressers and non-expressers).

METHODS

A total of 115 patients were included in this study. Genomic DNA was isolated from peripheral blood, and the real-time PCR technique was used to analyze the polymorphism POR rs1057868; C>T.

RESULTS

During the initial post-transplant period, variant allele carriers (*1/*28 and *28/*28) showed a lower TAC dose requirement than POR wild homozygotes (*1/*1). Regarding the influence of the different polymorphisms of POR within the CYP3A5 expresser and non-expresser groups, no differences were observed in any of the PK parameters analyzed during 12 months after transplantation.

CONCLUSION

In the studied population, the variant allelic POR*28 was significantly associated with lower TAC dose requirements and higher Co/D ratio in the first-month post-transplant. However, the effects of this polymorphism on the CYP3A5 enzyme activity were not observed.

Adrenal insufficiency is common amongst kidney transplant recipients receiving maintenance prednisolone and can be predicted using morning cortisol

BACKGROUND

Long-term glucocorticoid therapy is a key component of immunosuppression for kidney transplant recipients (KTRs), leading to significant cumulative glucocorticoid exposure. The aims of this study are to investigate the prevalence of adrenal insufficiency (AI) in KTRs taking prednisolone and to develop a screening algorithm to identify patients at the highest risk of AI.

METHODS

In this cross-sectional cohort study, 67 KTRs receiving prednisolone underwent a short synacthen test (SST) and measurement of cumulative glucocorticoid exposure.

RESULTS

A total of 72% (n = 48) of participants failed the SST. Participants with AI had a higher daily prednisolone dose (4.9 versus 4.2 mg/day; P = .002) and greater cumulative glucocorticoid exposure (289 versus 111 mg/kg; P = .03) than those with intact adrenal function. Participants with AI had lower baseline cortisol than participants with intact adrenal function (143 versus 303 nmol/L; P < .001). Morning cortisol of >288 nmol/L predicted a normal SST with 100% specificity [95% confidence interval (CI) 92-100] and 70% sensitivity (95% CI 56-78%), therefore excluding AI.

CONCLUSIONS

Our results suggest KTRs are at a higher risk for AI than previously reported. A morning serum cortisol measurement is a useful screening tool in this cohort, reducing the need for stimulatory testing by 44%. KTRs with AI need education regarding glucocorticoid sick rules, similar to patients with other forms of AI.

Prolonged-Release Once-Daily Formulation of Tacrolimus Versus Standard-of-Care Tacrolimus in de novo Kidney Transplant Patients Across Europe

Background: Tacrolimus is the calcineurin inhibitor of choice for preventing acute rejection episodes in kidney transplant patients. However, tacrolimus has a narrow therapeutic range that requires regular monitoring of blood concentrations to minimize toxicity. A new once-daily tacrolimus formulation, LCP-tacrolimus (LCPT), has been developed, which uses MeltDose™ drug-delivery technology to control drug release and enhance overall bioavailability. Our study compared dosing of LCPT with current standard-of-care tacrolimus [immediate-release tacrolimus (IR-Tac) or prolonged-release tacrolimus (PR-Tac)] during the 6 months following de novo kidney transplantation. Comparisons of graft function, clinical outcomes, safety, and tolerability for LCPT versus IR-Tac/PR-Tac were also performed.

Methods: Standard immunological risk patients with end-stage renal disease who had received a de novo kidney transplant were randomized (1:1) to LCPT (N = 200) or IR-Tac/PR-Tac (N = 201).

Results: Least squares (LS) mean tacrolimus total daily dose from Week 3 to Month 6 was significantly lower for LCPT than for IR-Tac/PR-Tac. Although LS mean tacrolimus trough levels were significantly higher for LCPT than IR-Tac/PR-Tac, tacrolimus trough levels remained within the standard reference range for most patients. There were no differences between the groups in treatment failure measures or safety profile.

Conclusion: LCPT can achieve similar clinical outcomes to other tacrolimus formulations, with a lower daily dose.

Clinical Trial Registration:https://clinicaltrials.gov/, identifier NCT02432833.

The Relationship between Initial Tacrolimus Metabolism Rate and Recipients Body Composition in Kidney Transplantation

There are several premises that the body composition of kidney transplant recipients may play a role in tacrolimus metabolism early after transplantation. The present study aimed at analyzing the relationship between the body composition parameters assessed by bioimpedance analysis (BIA) and initial tacrolimus metabolism. Immediately prior to transplantation, BIA using InBody 770 device was performed in 122 subjects. Tacrolimus concentration-to-dose (C/D) ratio was calculated based on the first blood trough level measurement. There was no difference in phase angle, visceral fat area, lean body mass index (LBMI) and the proportion of lean mass as a percentage of total body mass between the subgroups of slow and fast metabolizers. However, subjects with LBMI ≥ median value of 18.7 kg/m², despite similar initial tacrolimus dose per kg of body weight, were characterized by a significantly lower tacrolimus C/D ratio (median 1.39 vs. 1.67, respectively; p < 0.05) in comparison with the subgroup of lower LBMI. Multivariate regression analysis confirmed that age (r_partial = 0.322; p < 0.001) and LBMI (r_partial = −0.254; p < 0.01) independently influenced the tacrolimus C/D ratio. A LBMI assessed by BIA may influence the tacrolimus metabolism in the early post-transplant period and can be a useful in the optimization of initial tacrolimus dosing.

Genetic Polymorphisms Affecting Tacrolimus Metabolism and the Relationship to Post-Transplant Outcomes in Kidney Transplant Recipients

Background

Tacrolimus is a key drug in kidney transplantation with a narrow therapeutic index. However, whether tacrolimus exposure variability affects clinical outcomes and adverse reactions remains unknown.

Objective

Our study investigated the factors that influence tacrolimus exposure in kidney transplantation recipients and the relationship between tacrolimus concentration and clinical outcomes and adverse reactions.

Settings and Methods

We examined the effect of tacrolimus concentration on clinical outcomes and adverse reactions in 201 kidney transplantation recipients, and identified clinical and pharmacogenetic factors that explain tacrolimus exposure.

Results

The CYP3A5 genotype was clearly associated with dose-adjusted trough blood tacrolimus concentrations (C₀/D), whereas no significant difference was observed in patients with the CYP3A4*1B, CYP3A4*22, ABCB1, ABCC2, POR*28 or PXR alleles. Clinical factors such as red blood cell count, hemoglobin, and albumin were the most useful influence factors affecting tacrolimus C₀/D. Besides, Wuzhi capsule increased tacrolimus C₀/D in kidney transplantation recipients. Furthermore, higher tacrolimus concentrations were associated with higher diarrhea and post-transplant diabetes mellitus (PTDM) risk but not with acute rejection and chronic allograft kidney dysfunction.

Conclusion

Clinical factors, medication, and CYP-enzyme polymorphisms accounted for tacrolimus concentration variability in kidney transplantation recipients. Furthermore, higher tacrolimus concentrations were associated with higher diarrhea and PTDM risk.

Computational validation of ABCB1 gene polymorphism and its effect on tacrolimus dose concentration/levels in renal transplant individuals of South India

Patients with end-stage renal failure require hemodialysis and peritoneal dialysis; however, kidney transplantation is considered a better treatment option for renal failure patients, improving their quality of life and longevity. Among several potent immunosuppressive agents, tacrolimus (TAC) has shown progressive improvement in the graft survival rates after renal transplantation. Fifty kidney transplant patients undergoing TAC immunosuppressive treatment were included. The human genomic DNA was isolated using the phenol-chloroform extraction procedure. CYP3A5*6, CYP3A5*2, and ABCB1 exon 21 G2677 T/A polymorphisms were genotyped using the polymerase chain reaction-restriction fragment length polymorphism method. Fisher's exact test and Chi-square analysis were performed to analyze the data, where p < 0.05 was considered statistically significant. In addition, we implemented bioinformatics studies on ABCB1 protein to determine the mutation's effect sequentially and structurally. Among the genotyped single nucleotide polymorphisms (SNPs), SNPs of CYP3A5*2 and CYP3A5*6 did not vary in the studied population. The concentration/dose (C/D) ratio of TT genotype of the ABCB1 gene was higher (95% CI: 177.38-269.46) when compared to TA and AA. However, there were no substantial differences between the ABCB1 genotypes and TAC C/D ratio (p = 0.953). The TAC dose mg/kg/day (p = 0.002) and C/D ratio (p = 0.004) exhibited a statistically significant difference. However, no significant difference was found with respect to the ABCB1 gene between the non-toxicity and toxicity groups. Mutation and residue interaction analysis results showed that the S893T mutation destabilizes the ABCB1 protein, thus reducing the protein's flexibility. The present study demonstrated a substantial relationship between the TAC dose and C/D ratio, including the non-toxicity and toxicity groups. However, no possible correlation was observed between the ABCB1 gene polymorphism and renal transplant.

Tacrolimus Dose-Conversion Ratios Based on Switching of Formulations for Patients with Solid Organ Transplants

Background

Tacrolimus may be administered during hospitalization as an IV formulation or oral suspension. However, literature suggesting appropriate ratios for conversion from these formulations to capsules is limited.

Objective

To evaluate conversion ratios after a switch in formulation of tacrolimus for solid-organ transplant recipients.

Methods

This single-centre observational longitudinal study involved hospitalized patients who underwent a switch in formulation of tacrolimus according to 1 of 3 possible scenarios: IV to oral suspension, IV to capsule, or oral suspension to capsule. Data were collected from the earliest accessible electronic file (January 2009) to January 1, 2019. Conversion ratios were calculated for each of the 3 groups using data for blood concentrations and doses before and after the switch. The calculated ratios were then compared with recommended conversion ratios: 1:5 (i.e., 1 mg of IV tacrolimus is converted to 5 mg of oral tacrolimus, expressed as "5") for either of the switches involving an IV formulation and 1:1 (i.e., same amount, expressed as "1") for the switch from oral formulation to capsules.

Results

For the group who underwent switching from the IV formulation to oral suspension, the mean calculated conversion ratio was 3.04, which was significantly different from the recommended ratio of 5. For the group who underwent switching from the IV formulation to capsules, the calculated conversion ratio was 5.18, which was not significantly different from the recommended ratio of 5. For the group who underwent switching from oral suspension to capsules, the calculated conversion ratio was 1.17, which was not significantly different from the recommended ratio of 1.

Conclusion

In this small retrospective study of tacrolimus therapy, the calculated conversion ratio was significantly different from the recommended ratio for patients who were switched from IV administration to oral suspension, but not for those switched from IV administration or oral suspension to capsules. Therapeutic drug monitoring therefore appears indispensable, regardless of conversion ratios.

Effect of glecaprevir/pibrentasvir on weight-adjusted tacrolimus trough/dose ratios in heart and kidney transplant recipients

OBJECTIVE

The pharmacokinetic implications of direct-acting antiviral (DAA) use on tacrolimus posttransplant are unknown. This study sought to investigate the effects of glecaprevir/pibrentasvir (G/P), a CYP3A4 substrate and inhibitor, on weight-adjusted tacrolimus (FK) trough/dose ratio (T/D) following heart or kidney transplantation.

MATERIAL AND METHODS

This was a single-center, retrospective analysis of hepatitis C virus (HCV) viremic donors to HCV negative heart or kidney transplant recipients who received 12 weeks of G/P therapy. Weight-adjusted T/D was assessed while patients were at steady-state before, during, and after G/P treatment. Forty-one HCV negative recipients (three heart, 38 kidney) were evaluated.

RESULTS

The weight-adjusted T/D significantly increased during G/P treatment (119.31, IQR 88-173.8) compared to before G/P treatment (67.4, IQR 53.4-115.9) (p < 0.01), but decreased after completion of treatment (90.1, IQR 52.9-122.7) (p < 0.01). There was no difference in weight-adjusted T/D before and after G/P treatment (p = 0.42). Four patients experienced acute rejection.

CONCLUSION

Initiation of G/P in heart or kidney transplant recipients induces a reversible change in tacrolimus metabolism. A 33%-50% tacrolimus dose reduction may be considered at the time of G/P initiation. Regardless of tacrolimus dose adjustment, tacrolimus trough levels should be monitored 3 days after initiation of G/P. No clear relationship between HCV viremic organ transplantation and rejection risk was found. Larger studies are warranted to validate these findings.

Microbiome analysis, the immune response and transplantation in the era of next generation sequencing

The human gastrointestinal tract, skin and mucosal surfaces are inhabited by a complex system of bacteria, viruses, fungi, archaea, protists, and eukaryotic parasites with predominance of bacteria and bacterial viruses (bacteriophages). Collectively these microbes form the microbiota of the microecosystem of humans. Recent advancement in technologies for nucleic acid isolation from various environmental samples, feces and body secretions and advancements in shotgun throughput massive parallel DNA and RNA sequencing along with 16S ribosomal gene sequencing have unraveled the identity of otherwise unknown microbial entities constituting the human microecosystem. The improved transcriptome analysis, technological developments in biochemical analytical methods and availability of complex bioinformatics tools have allowed us to begin to understand the metabolome of the microbiome and the biochemical pathways and potential signal transduction pathways in human cells in response to microbial infections and their products. Also, developments in human whole genome sequencing, targeted gene sequencing of histocompatibility genes and other immune response associated genes by Next Generation Sequencing (NGS) have allowed us to have a better conceptualization of immune responses, and alloimmune responses. These modern technologies have enabled us to dive into the intricate relationship between commensal symbiotic and pathogenic microbiome and immune system. For the most part, the commensal symbiotic microbiota helps to maintain normal immune homeostasis besides providing healthy nutrients, facilitating digestion, and protecting the skin, mucosal and intestinal barriers. However, changes in diets, administration of therapeutic agents like antibiotics, chemotherapeutic agents, immunosuppressants etc. along with certain host factors including human histocompatibility antigens may alter the microbial ecosystem balance by causing changes in microbial constituents, hierarchy of microbial species and even dysbiosis. Such alterations may cause immune dysregulation, breach of barrier protection and lead to immunopathogenesis rather than immune homeostasis. The effects of human microbiome on immunity, health and disease are currently under intense research with cutting edge technologies in molecular biology, biochemistry, and bioinformatics along with tremendous ability to characterize immune response at single cell level. This review will discuss the contemporary status on human microbiome immune system interactions and their potential effects on health, immune homeostasis and allograft transplantation.

Precision Dosing for Tacrolimus Using Genotypes and Clinical Factors in Kidney Transplant Recipients of European Ancestry

Genetic variation in the CYP3A4 and CYP3A5 (CYP3A4/5) genes, which encode the key enzymes in tacrolimus metabolism, is associated with tacrolimus clearance and dose requirements. Tacrolimus has a narrow therapeutic index with high intra- and intersubject variability, in part because of genetic variation. High tacrolimus clearance and low trough concentration are associated with a greater risk for rejection, whereas high troughs are associated with calcineurin-induced toxicity. The objective of this study was to develop a model of tacrolimus clearance with a dosing equation accounting for genotypes and clinical factors in adult kidney transplant recipients of European ancestry that could preemptively guide dosing. Recipients receiving immediate-release tacrolimus for maintenance immunosuppression from 2 multicenter studies were included. Participants in the GEN03 study were used for tacrolimus model development (n = 608 recipients) and was validated by prediction performance in the DeKAF Genomics study (n = 1361 recipients). Nonlinear mixed-effects modeling was used to develop the apparent oral tacrolimus clearance (CL/F) model. CYP3A4/5 genotypes and clinical covariates were tested for their influence on CL/F. The predictive performance of the model was determined by assessing the bias (median prediction error [ME] and median percentage error [MPE]) and the precision (root median squared error [RMSE]) of the model. CYP3A5*3, CYP3A4*22, corticosteroids, calcium channel blocker and antiviral drug use, age, and diabetes significantly contributed to the interindividual variability of oral tacrolimus apparent clearance. The bias (ME, MPE) and precision (RMSE) of the final model was good, 0.49 ng/mL, 6.5%, and 3.09 ng/mL, respectively. Prospective testing of this equation is warranted.

CYP3A5*3 polymorphism and age affect tacrolimus blood trough concentration in myasthenia gravis patients

The study aims to identify clinical factors affecting tacrolimus blood trough concentration (C0) in myasthenia gravis (MG) patients and to optimize the initial dose of tacrolimus in MG treatment. A total of 103 MG patients participated in this study, and their clinical factors, medication regimens, C0 values and CYP3A5*3 polymorphisms were collected in detail. We used a linear mixed model to analyze the effect of multiple factors on the dosage-weighted C0 (C0:D) and performed subgroup analyses to investigate the consistency of correlations between influencing factors and the C0:D ratios. Among all factors, CYP3A5*3 polymorphism and age showed a strong positive correlation with C0:D ratios. The C0:D ratios (ng/ml·mg^-1) were higher for CYP3A5*3/*3 than for CYP3A5*1 (mean difference: 1.038, 95% confidence interval [CI]: 0.820-1.256, P-value <0.001), and for age in the range of 45-64 and ≥ 65 years than for age < 45 years (mean difference [95% CI] and P-value: 0.531[0.257-0.805] and P-value <0.001, 0.703 [0.377-1.029] and P-value <0.001, respectively). The C0:D ratios were not related to corticosteroid dosage, body weight, sex, hematocrit or the concomitant use of calcium channel blockers. The consistencies of the correlations between C0:D ratios and CYP3A5*3 polymorphism or age were confirmed by subgroup analyses. Thus, CYP3A5*3 polymorphism and age should be considered in optimizing the initial dose of tacrolimus for MG treatment.

Tacrolimus Exposure in Obese Patients: and A Case-Control Study in Kidney Transplantation

BACKGROUND

Tacrolimus pharmacokinetics in obese (Ob) patients has been poorly studied. In this article, the authors explored the impact of obesity on tacrolimus exposure in kidney transplant recipients (KTRs) and estimated a more suitable initial dosage in this population.

METHODS

A retrospective, observational, monocentric case-control study was performed in obese KTRs (BMI > 30 kg/m2) who received tacrolimus between 2013 and 2017 (initial dose: 0.15 mg/kg/d) (actual weight). Nonobese (Nob) controls (BMI <30 kg/m2) were matched for age and sex. Weekly centralized monitoring of tacrolimus trough levels was performed by liquid chromatography/mass spectrometry until the third month (M3). Target trough levels were set between 8 and 10 ng/mL. All patients received antilymphocyte globulin, corticosteroids, and mycophenolate mofetil.

RESULTS

Of the 541 KTRs, 28 tacrolimus-treated Ob patients were included and compared with 28 NOb-matched controls. With a mean of 22 assays/patient, tacrolimus trough levels were higher in Ob patients (mean 9.9 versus 8.7 ng/mL; P = 0.008); the weight-related dose of Tac was lower at M3 (mean 0.10 versus 0.13 mg/kg/d, P < 0.0001). The tacrolimus concentration to dose (C0/D) was higher in the Ob cohort [mean 116 versus 76 (ng/mL)/(mg/kg/d); P = 0.001]. In Ob patients, a mean decrease of -4.6 mg/d in the 3 months after tacrolimus initiation was required (versus -1.12 in NOb; P = 0.001) to remain within the therapeutic range. Obesity, high mycophenolate mofetil daily dose at M3, and CYP3A5 expression were independently associated with higher tacrolimus exposure. Four dose-adaptation strategies were simulated and compared with the study results.

CONCLUSIONS

An initial dose calculation based on either ideal or lean body weight may allow for faster achievement of tacrolimus trough level targets in Ob KTRs, who are at risk of overexposure when tacrolimus is initiated at 0.15 mg/kg/d. A prospective study is required to validate alternative dose calculation strategies in these patients.

Implications for body weight extremes in solid organ transplantation

The pharmacokinetic profiles of medications are altered in overweight and underweight patients, but few studies have described these differences in patients with body mass index extremes. As solid organ transplant programs expand their candidate selection criteria to accommodate a growing population of patients with weight extremes, it has become imperative to understand and evaluate the impact weight extremes have on the pharmacokinetics of life-sustaining immunosuppression in this population. This review will describe pharmacokinetic and dosing considerations for weight extremes in solid organ transplant recipients, including changes following bariatric surgeries, non-pharmacologic and pharmacologic management strategies for weight loss and gain, and potential drug-drug interactions with popular weight management products.

Analyses of AUC(0–12) and C0 Compliances within Therapeutic Ranges in Kidney Recipients Receiving Cyclosporine or Tacrolimus

The AUC (area under the concentration time curve) is considered the pharmacokinetic exposure parameter best associated with clinical effects. Unfortunately, no prospective studies of clinical outcomes have been conducted in adult transplant recipients to investigate properly the potential benefits of AUC_(0–12) monitoring compared to the C₀-guided therapy. The aim of the present study was to compare two methods, C₀ (through level) and AUC_(0–12) (area under the concentration time curve), for assessing cyclosporine and tacrolimus concentrations. The study included 340 kidney recipients. The AUC_(0–12) was estimated using a Bayesian estimator and a three-point limited sampling strategy. Therapeutic drug monitoring of tacrolimus performed by using AUC_(0–12) and C₀ showed that tacrolimus in most cases is overdosed when considering C₀, while determination of the AUC_(0–12) showed that tacrolimus is effectively dosed for 27.8–40.0% of patients receiving only tacrolimus and for 25.0–31.9% of patients receiving tacrolimus with MMF (mycophenolate mofetil). In the 1–5 years post-transplantation group, 10% higher CsA (cyclosporine) dose was observed, which was proportionate with a 10% higher AUC_(0–12) exposure value. This indicates good compatibility of the dosage and the AUC(0–12) method. The Bland–Altman plot demonstrated that C₀ and AUC_(0–12) might be interchangeable methods, while the ROC (receiver operating characteristic) curve analysis of the C₀/AUC_(0–12) ratio in the tacrolimus-receiving patient group demonstrated reliable performance to predict IFTA (interstitial fibrosis and tubular atrophy) after kidney transplantation, with an ROC curve of 0.660 (95% confidence interval (CI): 0.576–0.736), p < 0.01. Moreover, AUC_(0–12) and C₀ of tacrolimus depend on concomitant medication and adjustment of the therapeutic range for AUC_(0–12) might influence the results.

Clinical Factors Affecting the Dose Conversion Ratio from Intravenous to Oral Tacrolimus Formulation among Pediatric Hematopoietic Stem Cell Transplantation Recipients

BACKGROUND

Tacrolimus is converted from intravenous to oral formulation for the prophylaxis of graft-versus-host disease when patients can tolerate oral intake and graft-versus-host disease is under control. Oral tacrolimus formulation presents poor bioavailability with intraindividual and interindividual variations; however, some factors affecting its blood concentration among pediatric hematopoietic stem cell transplantation (HCT) recipients are still unclear. This study aimed to identify the clinical factors affecting tacrolimus blood concentrations after switching its formulation.

METHODS

Changes in the blood concentration/dose ratio (C/D) of tacrolimus in pediatric HCT recipients were analyzed after the switching of tacrolimus from intravenous to oral formulation. Clinical records of 57 pediatric patients who underwent allogenic HCT from January 2006 to April 2019 in our institute were retrospectively reviewed. The C/D of tacrolimus before discontinuation of intravenous infusion (C/Div) was compared with the tacrolimus trough level within 10 days after the initiation of oral administration (C/Dpo). Multiple linear regression analysis was performed to identify factors affecting (C/Dpo)/(C/Div).

RESULTS

The constant coefficient of (C/Dpo)/(C/Div) was 0.1692 [95% confidence interval (CI), 0.137-0.2011]. The concomitant use of voriconazole or itraconazole and female sex were significant variables with a beta coefficient of 0.0974 (95% CI, 0.062-0.133) and -0.0373 (95% CI, -0.072 to -0.002), respectively.

CONCLUSIONS

After switching of tacrolimus formulation, pediatric HCT recipients might need oral tacrolimus dose that is 5-6 and 3.5-4.5 times the intravenous dose to maintain tacrolimus blood concentrations and area under the concentration-time curve, respectively. With the concomitant use of voriconazole or itraconazole, an oral tacrolimus dose of 4-5 times the intravenous dose seemed appropriate to maintain blood tacrolimus concentration.

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.

Flucloxacillin decreases tacrolimus blood trough levels: a single-center retrospective cohort study

Purpose

Tacrolimus and everolimus are widely used to prevent allograft rejection. Both are metabolized by the hepatic cytochrome P450 (CYP) enzyme CYP3A4 and are substrate for P-glycoprotein (P-gp). Drugs influencing the activity or expression of CYP enzymes and P-gp can cause clinically relevant changes in the metabolism of immunosuppressants. Several case reports have reported that flucloxacillin appeared to decrease levels of drugs metabolized by CYP3A4 and P-gp. The magnitude of this decrease has not been reported yet.

Methods

In this single-center retrospective cohort study, we compared the tacrolimus and everolimus blood trough levels (corrected for the dose) before, during, and after flucloxacillin treatment in eleven transplant patients (tacrolimus n = 11 patients, everolimus n = 1 patient, flucloxacillin n = 11 patients).

Results

The median tacrolimus blood trough level decreased by 37.5% (interquartile range, IQR 26.4–49.7%) during flucloxacillin treatment. After discontinuation of flucloxacillin, the tacrolimus blood trough levels increased by a median of 33.7% (IQR 22.5–51.4%). A Wilcoxon signed-rank test showed statistically significantly lower tacrolimus trough levels during treatment with flucloxacillin compared with before (p = 0.009) and after flucloxacillin treatment (p = 0.010). In the only available case with concomitant everolimus and flucloxacillin treatment, the same pattern was observed.

Conclusions

Flucloxacillin decreases tacrolimus trough levels, possibly through a CYP3A4 and/or P-gp-inducing effect. It is strongly recommended to closely monitor tacrolimus and everolimus trough levels during flucloxacillin treatment and up to 2 weeks after discontinuation of flucloxacillin.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-02968-z) contains supplementary material, which is available to authorized users.

Effect of Concentration/Dose Ratio in De Novo Kidney Transplant Recipients Receiving LCP-Tacrolimus or Immediate-Release Tacrolimus: Post Hoc Analysis of a Phase 3 Clinical Trial

Background

A previous phase 3 clinical trial in de novo adult kidney transplant recipients (NCT01187953) compared the efficacy and safety of once-daily LCP-tacrolimus (LCPT) and twice-daily immediate-release tacrolimus (IR-Tac). However, whether the rate of tacrolimus metabolism affects outcomes between LCPT and IR-Tac was not examined.

Material/Methods

Patients were initiated on 0.17 mg/kg/day LCPT or 0.1 mg/kg/day IR-Tac, with doses adjusted over time to maintain target therapeutic trough concentrations. This post hoc analysis examined dosing trends, relative efficacy, and safety of LCPT (n=247) and IR-Tac (n=249) in slow, intermediate, and rapid metabolizers as defined by concentration/dose ratios at day 30.

Results

For all metabolizer subgroups, minimum target tacrolimus trough concentrations were obtained more rapidly with LCPT than with IR-Tac. Slow metabolizers were more likely to exceed target trough concentrations with LCPT, while rapid metabolizers were more likely to fall below target trough concentrations with IR-Tac. Regardless of metabolizer status, significant differences were not detected between LCPT and IR-Tac for treatment failure, death, graft failure, biopsy-proven acute rejection, estimated glomerular filtration rate, or other clinical outcomes.

Conclusions

Although within metabolizer subgroups, attainment of target trough concentrations in the first week differed between LCPT and IR-Tac, these results suggest that, regardless of metabolizer phenotype, clinical outcomes do not differ between these formulations when dose adjustments are made.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT01187953

Effects of CYP3A5 Polymorphisms on Efficacy and Safety of Tacrolimus Therapy in Patients with Idiopathic Membranous Nephropathy

Background

Tacrolimus (TAC) is beneficial for patients with idiopathic membranous nephropathy (IMN). It has a narrow therapeutic concentration range and many factors influence TAC blood concentration. CYP3A5 is the most important enzyme in TAC metabolism. The aim of this study was to analyze the effects of CYP3A5 gene polymorphisms on the efficacy and safety of TAC in IMN patients.

Patients and Methods

Patients with IMN who received oral TAC (0.05-0.075mg/kg/day) combined with prednisone (0.5mg/kg/day) from March 2016 to October 2018 were included. The data of clinical characteristics, therapeutic drugs and adverse reactions of patients were collected at baseline and during 24 weeks of treatment. Patients were divided into two groups according to different CYP3A5 genetic polymorphisms. The significant differences in the efficacy and side effects between the two groups were analyzed.

Results

A total of 76 patients who completed follow-up were divided into CYP3A5 nonexpresser (CYP3A5*3/*3) group and CYP3A5 expresser (CYP3A5 *1/*3) group. The significant association between the CYP3A5 phenotype and TAC metabolism was observed. A total of 43 case-times patients exhibited adverse effects. The infection rate in CYP3A5 nonexpresser group (21.95%) was remarkably higher than the rate in CYP3A5 expresser group (5.71%). Blood concentration and C₀/D levels were risk factors for adverse events through logistic regression analysis. There was no statistical difference between the study groups with respect to the efficacy.

Conclusion

Our results demonstrated that CYP3A5 polymorphisms had important guiding roles in the treatment of IMN with tacrolimus. CYP3A5 expressers required higher daily doses of TAC to achieve the target drug concentration, but with fewer side effects. CYP3A5 genetic polymorphism might be used for TAC dosing adjustment to optimize the treatment for patients with IMN.

CYP3A5 gene polymorphisms and their impact on dosage and trough concentration of tacrolimus among kidney transplant patients: a systematic review and meta-analysis

Tacrolimus is an immunosuppressive drug widely used in kidney transplantation. Cytochrome P450 3A5 (CYP3A5) protein is involved in tacrolimus metabolism. Single nucleotide polymorphism in the CYP3A5 gene (6986A>G) results in alteration in metabolic activity of CYP3A5 protein which eventually affects the tacrolimus concentration. Patients with CYP3A5 expresser genotypes (A/A *1/*1 and A/G *1/*3) metabolize tacrolimus more rapidly than CYP3A5 nonexpressers (G/G *3/*3). We performed meta-analysis to estimate the effect of CYP3A5 polymorphism on the trough concentration-dose ratio (Co/D) and risk of renal allograft rejection with similar post-transplant periods and Asian vs. European populations. Our results showed that the tacrolimus Co/D ratio is significantly lower in CYP3A5 expresser group as compared with nonexpresser in Asian as well as in European populations at any post-transplant period (p < 0.00001). No significant association was found with renal allograft rejection episodes between expressers and nonexpressers in European populations (OR: 1.12; p = 0.47). Interestingly, Asian population (with expresser genotypes) and patients after 3 years post-transplantation (with expresser genotypes) have a higher risk of rejection (OR: 1.62; p < 0.05), (OR: 1.68; p < 0.05), respectively. This could be due to high prevalence of expresser genotypes in Asian population. Few tacrolimus-based studies are identified with long-term graft survival. There is a need to have more studies looking for long-term graft survival in expresser as well as no-expresser groups especially in Asian populations who have high frequency of CYP3A5 functional genotype.

Tacrolimus: Influence of the Posttransplant Concentration/Dose Ratio on Kidney Graft Function in a Two-Year Follow-Up

INTRODUCTION

Tacrolimus (TAC) metabolism rate has the potential to impact graft function after kidney transplantation (KTx). We aimed to analyze the relationship between the early post-KTx TAC C/D ratio (blood trough concentration normalized by total daily dose) and kidney graft function in a 2-year follow-up.

METHODS

We retrospectively analyzed data from 101 post-KTx patients at 3, 6, 12, and 24 months after KTx to identify the C/D ratio cutoff value optimal for dividing patients into fast and slow TAC metabolizers. We investigated the relationship between their TAC metabolism rate and graft function.

RESULTS

Patients were divided based on the TAC C/D ratio at 6 months after KTx of 1.47 ng/mL * 1 mg. Fast metabolizers (C/D ratio <1.47 ng/mL * 1 mg) presented with significantly worse graft function throughout the whole study period (p < 0.05 at each timepoint) and were significantly less likely to develop good graft function (estimated glomerular filtration rate ≥45 mL/min/1.73 m2) than slow metabolizers. Our model based on donor and recipient age, recipient sex and slow/fast metabolism status allowed for identification of patients with compromised graft function in 2-year follow-up with 66.7% sensitivity and 94.6% specificity.

CONCLUSION

Estimating TAC C/D ratio at 6 months post-KTx might help identify patients at risk of developing deteriorated graft function in a 2-year follow-up.

A randomized, open-label pharmacokinetic trial of tacrolimus extended-release dosing in obese de novo kidney transplant recipients

PURPOSE

Tacrolimus extended-release (TAC-ER; Astagraf XL^® ) is utilized in many immunosuppressive regimens post-renal transplantation. Current dosing recommendation for the TAC-ER in renal transplant is 0.15-0.2 mg/kg/day administered once daily. The purpose of this study was to determine the best method of dosing TAC-ER in obese renal transplant recipients.

METHODS

De novo obese kidney transplant recipients were randomized to receive TAC-ER 0.15 mg/kg/day based on either adjusted body weight (aBW) or ideal body weight (IBW). Post-transplant patients underwent three pharmacokinetic assessments over 14 days. The primary endpoint was the difference in TAC-ER exposure (AUC0-24) in obese patients dosed using aBW compared with IBW.

RESULTS

A total of 20 obese renal transplant recipients were randomized to participate in the study (10 aBW and 10 IBW). Results of the primary outcome (AUC0-24) on Study Day 1, 7, and 14 were not statistically different between the two groups. There was no difference in the number of days to therapeutic trough concentration between the two dosing weights (aBW = 5.1, IBW = 4.9, days; P = 0.90).

CONCLUSION

In a population of obese renal transplant recipients, comparable trough concentrations and overall exposure in both groups indicate that IBW may be preferred, as less initial drug was needed to attain adequate exposure.

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

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

Prior Amiodarone Exposure Reduces Tacrolimus Dosing Requirements in Heart Transplant Recipients

Introduction:

Amiodarone use prior to heart transplant is independently associated with a higher rate of severe primary graft dysfunction and in-hospital mortality. Amiodarone may also alter the pharmacokinetics of medications metabolized via cytochrome P450. No data exist regarding the interaction between pretransplant amiodarone and tacrolimus concentrations.

Design:

Single-center retrospective study of transplant patients between January 1, 2014, and June 30, 2016. A therapeutic tacrolimus concentration was defined as a trough level between 8 and 15 ng/mL for 2 consecutive days. The primary outcome was the tacrolimus therapeutic weight-based dosing requirements (mg/kg/day) for patients receiving amiodarone prior to transplant when compared to those without prior receipt of amiodarone. Secondary outcomes include the incidence of cellular rejection and mortality within 6 months posttransplant.

Results:

Multi-organ transplant recipients (n = 3), retransplants (n = 9), those who died prior to a therapeutic level (n = 1), and those receiving amiodarone posttransplant (n = 7) were excluded from the analysis. Of the 80 patients included, 34 (42%) received amiodarone prior to transplant. Patient characteristics were similar, with the exception of primary graft dysfunction incidence (38% in amiodarone vs 8.5% in control, P = .001). The median therapeutic dose was 0.1 (interquartile range [IQR]: 0.07-0.12) versus 0.13 (IQR: 0.09-0.17) in the amiodarone and control groups, respectively, ( P < .01). No significant difference in mortality or rejection was noted.

Conclusion:

Patients receiving amiodarone prior to transplant require a lower weight-based dose of tacrolimus.

Pharmacokinetics of Prolonged-Release Once-Daily Formulations of Tacrolimus in De Novo Kidney Transplant Recipients: A Randomized, Parallel-Group, Open-Label, Multicenter Study

INTRODUCTION

Different prolonged-release formulations of tacrolimus are available. To date, the pharmacokinetic (PK) profile of LCP-tacrolimus (LCPT; Envarsus^®) has not been compared with PR-Tac (Advagraf^®) in de novo kidney transplant recipients. These profiles will guide clinical recommendations for the initiation and dose titration strategies of once-daily tacrolimus formulations.

METHODS

This randomized, parallel-group, open-label, multicenter PK study randomized 75 de novo, adult, white kidney transplant recipients to LCPT 0.17 mg/kg/day (n = 37) or PR-Tac 0.20 mg/kg/day (n = 38) for 4 weeks. Dose adjustments were permitted to target a pre-defined therapeutic range based on measured trough blood concentrations.

RESULTS

PK analysis (days 1, 3, 7 and 14) included 68 patients (LCPT, n = 33; PR-Tac, n = 35). Similar proportions of patients were within the pre-defined therapeutic tacrolimus trough blood concentration range, with < 12% in each group having below-target trough levels over the study period. LCPT demonstrated ~ 30% greater relative bioavailability [LCPT/PR-Tac adjusted geometric mean ratio: day 3, 1.32 (p = 0.007); day 7, 1.25 (p = 0.051); day 14, 1.43 (p = 0.002)] and ~ 30% lower peak-to-trough percentage fluctuation of blood concentration [LCPT/PR-Tac adjusted geometric mean ratio: day 3, 0.70 (p < 0.001); day 7, 0.68 (p < 0.001); day 14, 0.73 (p = 0.004)] in addition to longer time to maximum blood concentration (t_max), lower maximum concentration (C_max) and a consistently lower daily dose (~ 40% dose reduction with LCPT vs. PR-Tac by day 28). Safety profiles were similar.

CONCLUSION

In de novo kidney transplant recipients, prolonged-release formulations of tacrolimus can reach therapeutic concentrations in the immediate post-transplant period. LCPT has greater relative bioavailability and lower peak-to-trough fluctuation compared with PR-Tac.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov; study number NCT02500212.

FUNDING

Chiesi Farmaceutici S.p.A.

Impact of POR and CYP3A5 Polymorphisms on Trough Concentration to Dose Ratio of Tacrolimus in the Early Post-operative Period Following Kidney Transplantation

BACKGROUND

Tacrolimus, a critical dose drug, is widely used in transplantation. Knowing the contribution of genetic factors, which significantly influence tacrolimus variability, is beneficial in the personalization of its starting dose. The significant impact of CYP3A5*3 polymorphisms on tacrolimus exposure has been reported. Conflicting results of the additional influence of POR*28 polymorphisms on tacrolimus pharmacokinetic interindividual variability have been observed among different populations. The objective of this study was to explore the interaction between POR*28 and CYP3A5*3 polymorphisms and their main effects on tacrolimus trough concentration to dose ratios on day 7 after kidney transplantation.

METHODS

Two hundred sixteen adult kidney transplant recipients participated in this retrospective study. All participants received a twice daily tacrolimus regimen. Blood samples and data were collected on day 7 after transplantation. A 2-way analysis of covariance was performed. Tested covariates were age, hemoglobin, serum albumin, and prednisolone dose.

RESULTS

A 2 × 2 analysis of covariance revealed that the interaction between CYP3A5 polymorphisms (CYP3A5 expresser and CYP3A5 nonexpresser) and POR polymorphisms (POR*28 carrier and POR*28 noncarrier) was not significant (F(1, 209) = 2.473, P = 0.117, (Equation is included in full-text article.)= 0.012). The predicted main effect of CYP3A5 and POR polymorphisms was significant (F(1, 209) = 105.565, P < 0.001, (Equation is included in full-text article.)= 0.336 and F(1, 209) = 4.007, P = 0.047, (Equation is included in full-text article.)= 0.019, respectively). Hemoglobin, age, and steroid dose influenced log C0/dose of tacrolimus (F(1, 209) = 20.612, P < 0.001, (Equation is included in full-text article.)= 0.090; F(1, 209) = 14.360, P < 0.001, (Equation is included in full-text article.)= 0.064; and F(1, 209) = 5.512, P = 0.020, (Equation is included in full-text article.)= 0.026, respectively).

CONCLUSIONS

After adjusting for the influences of hemoglobin, age, and prednisolone dose, significant impacts of the CYP3A5 and POR polymorphisms on tacrolimus exposure were found. The effect of POR*28 and CYP3A5*3 polymorphisms during the very early period after kidney transplantation is independent of each other.

No Significant Influence of Reduced Initial Tacrolimus Dose on Risk of Underdosing and Early Graft Function in Older and Overweight Kidney Transplant Recipients

BACKGROUND

Nowadays, a reduced initial daily dose of tacrolimus (Tac) (0.1-0.15 mg/kg) is recommended for the majority of kidney transplant recipients (KTRs). The aim of the study was to analyze the safety of such a regimen, including the risk of first inadequately low Tac blood level, acute rejection (AR) occurrence, or early graft dysfunction.

METHODS

In 2011, we introduced a modified (0.1-0.15 mg/kg/d) initial Tac dosing regimen in older (>55 years) and/or overweight KTRs. To assure the safety of this protocol, we monitored the risk of inadequately low blood Tac level (<6 ng/mL) and incidence of AR or delayed graft function (DGF). The historical cohort with the higher Tac dosing regimen (0.2 mg/kg/d, n = 208) served as a control group.

RESULTS

The mean Tac daily dose in 78 KTRs (group with reduced dosing) was 0.133 (95% confidence interval [CI], 0.130-0.136) mg/kg and was significantly lower than the standard, previously prescribed dose of 0.195 (95% CI, 0.194-0.197) mg/kg. Of note, induction therapy was employed twice more often in the reduced Tac dosing group. The dose reduction resulted in a slight, nonsignificant decrease in first Tac trough level. The percentages of patients with first Tac troughs <6 ng/mL (5.1% vs 4.8%), AR (6.4% vs 5.8%), and DGF (25.6% vs 31.2%) were similar in the reduced and standard dosing groups.

CONCLUSION

The currently recommended reduction in Tac initial dosing does not increase the risk of inadequate immunosuppression and does not affect the early graft function. Regardless of Tac dose reduction, there is still a substantial risk of Tac overdosing in older or overweight KTRs.

Living Donor Intestinal Transplantation

Living donor intestinal transplantation (LDIT) has been improved leading to results comparable to those obtained with deceased donors. LDIT should be limited to specific indications and patient selection. The best indication is combined living donor intestinal/liver transplantation in pediatric recipients with intestinal and hepatic failure; the virtual elimination of waiting time may avoid the high mortality experienced by candidates on the deceased waiting list. Potentially, LDIT could be used in highly sensitized recipients to allow the application of de-sensitization protocols. In the case of available identical twins or HLA-identical sibling, LDIT has a significant immunologic advantage and should be offered.

Risk factors for calcineurin inhibitor nephrotoxicity after renal transplantation: a systematic review and meta-analysis

Background

Nephrotoxicity of calcineurin inhibitors (CNIs) is the major concern for long-term allograft survival despite its predominant role in current immunosuppressive regime after renal transplantation. CNI nephrotoxicity is multifactorial with demographic, environmental, and pharmacogenetic flexibility, whereas studies indicating risk factors for CNI nephrotoxicity obtained incomplete or conflicting results.

Methods

A systematic review and meta-analysis of risk factors for CNI nephrotoxicity was performed on all retrieved studies through a comprehensive research of network database. Data were analyzed by Review Manager 5.2 with heterogeneity assessed using the Cochrane Q and I² tests. CNI nephrotoxicity was primarily indicated with protocol biopsy or index-based clinical diagnosis, and the secondary outcome was defined as delayed graft function.

Results

Twelve observational studies containing a total of 2,849 cases were identified. Donor age (odds ratio [OR], 1.01; 95% CI, 1.01-1.03; p=0.02), recipient zero-time arteriosclerosis (OR, 1.44; 95% CI, 1.04-1.99; p=0.03), and CYP3A5*3/*3 genotype (OR, 2.80; 95% CI, 2.63-2.98; p=0.00) were confirmed as risk factors for CNI nephrotoxicity. Subgroup and sensitivity analysis claimed donor age as a significant contributor in Asian and Caucasian areas.

Conclusion

Older donor age, recipient zero-time arteriosclerosis, and CYP3A5*3/*3 genotype might add up the risk for CNI nephrotoxicity, which could be interpreted into a robust biomarker system.

Which Kidney Transplant Recipients Can Benefit from the Initial Tacrolimus Dose Reduction?

Background

Observational data suggest that the fixed initial recommended tacrolimus (Tc) dosing (0.2 mg/kg/day) results in supratherapeutic drug levels in some patients during the early posttransplant period. The aim of the study was to analyze a wide panel of patient-related factors and their interactions which increase the risk for first Tc blood level > 15 ng/ml.

Materials and Methods

We performed a retrospective analysis of 488 consecutive adult kidney transplant recipients who were initially treated with triple immunosuppressive regimen containing tacrolimus twice daily. The analysis included the first assessment of Tc trough blood levels and several demographic, anthropometric, laboratory, and comedication data.

Results

The multiple logistic regression analysis showed that age > 55 years, BMI > 24.6 kg/m², blood hemoglobin concentration > 9.5 g/dl, and the presence of anti-HCV antibodies independently increased the risk for first Tc level > 15 ng/ml. The relative risk (RR) for first tacrolimus level > 15 ng/ml was 1.88 (95% CI 1.35–2.64, p < 0.001) for patients with one risk factor and 2.81 (2.02–3.89, p < 0.001) for patients with two risk factors.

Conclusions

Initial tacrolimus dose reduction should be considered in older, overweight, or obese kidney transplant recipients and in subjects with anti-HCV antibodies. Moreover, dose reduction of tacrolimus is especially important in patients with coexisting multiple risk factors.

Gene Variations of Sixth Complement Component Affecting Tacrolimus Metabolism in Patients with Liver Transplantation for Hepatocellular Carcinoma

BACKGROUND

Orthotopic liver transplantation (OLT) improves the prognosis of patients with hepatocellular carcinoma (HCC). Moreover, the complement system is a powerful immune effector that can affect liver function and process of liver cirrhosis. However, studies correlating the complement system with tacrolimus metabolism after OLT are scarce. In this study, the role of single nucleotide polymorphisms (SNPs) associated with the sixth complement component (C6) in tacrolimus metabolism was investigated during the early stages of liver transplantation.

METHODS

The study enrolled 135 adult patients treated with OLT for HCC between August 2011 and October 2013. Ten SNPs in C6 gene and rs776746 in cytochrome P450 3A5 (CYP3A5) gene were investigated. The tacrolimus levels were monitored daily during 4 weeks after transplantation.

RESULTS

Both donor and recipient CYP3A5 rs776746 allele A were correlated with decreased concentration/dose (C/D) ratios. Recipient C6 rs9200 allele G and donor C6 rs10052999 homozygotes were correlated with lower C/D ratios. Recipient CYP3A5 rs776746 allele A (yielded median tacrolimus C/D ratios of 225.90 at week 1 and 123.61 at week 2), C6 rs9200 allele G (exhibited median tacrolimus C/D ratios of 211.31 at week 1, 110.23 at week 2, and 99.88 at week 3), and donor CYP3A5 rs776746 allele A (exhibited median C/D ratios of 210.82 at week 1, 111.06 at week 2, 77.49 at week 3, and 85.60 at week 4) and C6 rs10052999 homozygote (exhibited median C/D ratios of 167.59 at week 2, 157.99 at week 3, and 155.36 at week 4) were associated with rapid tacrolimus metabolism. With increasing number of these alleles, patients were found to have lower tacrolimus C/D ratios at various time points during the 4 weeks after transplantation. In multiple linear regression analysis, recipient C6 rs9200 group (AA vs. GG/GA) was found to be related to tacrolimus metabolism at weeks 1, 2, and 3 (P = 0.005, P = 0.045, and P = 0.033, respectively), whereas donor C6 rs10052999 group (CC/TT vs. TC) was demonstrated to be correlated with tacrolimus metabolism only at week 4 (P = 0.001).

CONCLUSIONS

Recipient C6 gene rs9200 polymorphism and donor C6 gene rs10052999 polymorphism are new genetic loci that affect tacrolimus metabolism in patients with HCC after OLT.

Sex Differences in the Blood Concentration of Tacrolimus in Systemic Lupus Erythematosus and Rheumatoid Arthritis Patients with CYP3A5*3/*3

The purpose of this study was to describe the impact of sex and cytochrome P450 3A5 (CYP3A5) variant on the blood concentration of tacrolimus in patients with systemic lupus erythematosus or rheumatoid arthritis. The blood concentration of tacrolimus (ng/mL) divided by the daily dose of tacrolimus (mg/day) and the patient's weight (kg) (C/D) was obtained from 55 patients. The C/D value was analysed according to genetic variation in CYP3A5 or ATP binding cassette subfamily B member 1 (ABCB1), sex, and age. The C/D value in the CYP3A5*3/*3 group was significantly higher than in the CYP3A5*1/*1 and *1/*3 groups (p < 0.05, effect size: d = 1.40). In the CYP3A5*3/*3 group, the concentration of tacrolimus was significantly higher in men than in women (p < 0.05, effect size: d = 1.78). Furthermore, in the CYP3A5*3/*3 group, the concentration of tacrolimus was significantly higher in women aged over 50 years than in women aged under 50 years (p < 0.05, effect size: d = 1.18). In contrast, ABCB1 genetic variations did not show any significant effect on the C/D value. Since the blood concentration of tacrolimus in patients with CYP3A5*3/*3 varies depending on sex and age, these factors should be considered when studying the difference of sex in CYP3A.

Influence of tacrolimus metabolism rate on renal function after solid organ transplantation

The calcineurin inhibitor (CNI) tacrolimus (TAC) is an integral part of the immunosuppressive regimen after solid organ transplantation. Although TAC is very effective in prevention of acute rejection episodes, its highly variable pharmacokinetic and narrow therapeutic window require frequent monitoring of drug levels and dose adjustments. TAC can cause CNI nephrotoxicity even at low blood trough levels (4-6 ng/mL). Thus, other factors besides the TAC trough level might contribute to CNI-related kidney injury. Unfortunately, TAC pharmacokinetic is determined by a whole bunch of parameters. However, for daily clinical routine a simple application strategy is needed. To address this problem, we and others have evaluated a simple calculation method in which the TAC blood trough concentration (C) is divided by the daily dose (D). Fast TAC metabolism (C/D ratio < 1.05) was identified as a potential risk factor for an inferior kidney function after transplantation. In this regard, we recently showed a strong association between fast TAC metabolism and CNI nephrotoxicity as well as BKV infection. Therefore, the TAC C/D ratio may assist transplant clinicians in a simple way to individualize the immunosuppressive regimen.

Donor CYP3A5 genotype influences tacrolimus disposition on the first day after paediatric liver transplantation

AIM

The aim of the present study was to investigate the influence of the cytochrome P450 (CYP) 3A4/5 genotype in paediatric liver transplant recipients and donors, and the contribution of age and gender to tacrolimus disposition on the first day after transplantation.

METHODS

The contribution of the CYP3A4/5 genotype in paediatric liver transplant recipients and donors to the tacrolimus blood trough concentrations (C₀ ) and the tacrolimus concentration/weight-adjusted dose ratio on day 1 was evaluated in 67 liver-transplanted children: 33 boys and 34 girls, mean age 4.5 years.

RESULTS

Donor CYP3A5 genotype appears to be significantly associated with tacrolimus disposition on the first day after liver transplantation (P < 0.0002). Other physiological factors, such as recipient age and donor gender may also play a role and lead to significant differences in tacrolimus C₀ and tacrolimus concentration/weight-adjusted dose ratio on day 1. However, according to the general linear model, only recipient age appears to be independently associated with tacrolimus disposition on the first day after liver transplantation (P < 0.03). Indeed, there was a faster tacrolimus metabolism in children under 6 years of age (P < 0.02).

CONCLUSIONS

Donor CYP3A5 genotype, recipient age and, to a lesser extent, donor gender appear to be associated with tacrolimus disposition on day 1 after transplant. This suggests that increasing the starting tacrolimus doses in paediatric patients under 6 years of age who receive a graft from a male extensive metabolizer may enhance the possibility of their tacrolimus levels reaching the therapeutic range sooner.

The effect of CYP3A5 genetic polymorphisms on adverse events in patients with ulcerative colitis treated with tacrolimus

BACKGROUND

Tacrolimus is an immunosuppressive agent, used in the remission induction therapy of ulcerative colitis (UC).

AIMS

We investigated the correlation between CYP3A5 genetic polymorphisms and the adverse events in patients with UC. The pharmacokinetics of tacrolimus after oral administration were also analyzed.

METHODS

We enrolled 29 hospitalized patients with UC received oral tacrolimus. Genotyping for CYP3A5 A6986G (rs776746) was performed using Custom TaqMan^® SNP genotyping assays. Adverse events, concentration and dose (C/D) ratios and clinical outcomes were investigated.

RESULTS

CYP3A5 expressers and non-expressers were 16 and 13, respectively. C/D ratios of CYP3A5 expressers were significantly lower compared to non-expressers. The response rate in CYP3A5 non-expressers was relatively higher in the early phase of treatment compared to expressers, but not statistically significant. The incidence of overall adverse events was significantly higher in CYP3A5 expressers than in non-expressers (P=0.034, chi-squared test). In particular, the incidence of nephrotoxicity was significantly higher in CYP3A5 expressers compared to non-expressers (P=0.027, chi-squared test). All of the nephrotoxicity were reversible and resolved by discontinuation or dose reduction of tacrolimus.

CONCLUSION

The adverse events especially nephrotoxicity were frequently observed in CYP3A5 expressers. CYP3A5 expressers should be paid attention to the onset of nephrotoxicity.

Influence of tacrolimus metabolism rate on BKV infection after kidney transplantation

Immunosuppression is the major risk factor for BK virus nephropathy (BKVN) after renal transplantation (RTx). As the individual tacrolimus (Tac) metabolism rate correlates with Tac side effects, we hypothesized that Tac metabolism might also influence the BKV infection risk. In this case-control study RTx patients with BK viremia within 4 years after RTx (BKV group) were compared with a BKV negative control group. The Tac metabolism rate expressed as the blood concentration normalized by the daily dose (C/D ratio) was applied to assess the Tac metabolism rate. BK viremia was detected in 86 patients after a median time of 6 (0–36) months after RTx. BKV positive patients showed lower Tac C/D ratios at 1, 3 and 6 months after RTx and were classified as fast Tac metabolizers. 8 of 86 patients with BK viremia had histologically proven BKN and a higher median maximum viral load than BKV patients without BKN (441,000 vs. 18,572 copies/mL). We conclude from our data that fast Tac metabolism (C/D ratio <1.05) is associated with BK viremia after RTx. Calculation of the Tac C/D ratio early after RTx, may assist transplant clinicians to identify patients at risk and to choose the optimal immunosuppressive regimen.

Metabolic consequences of modern immunosuppressive agents in solid organ transplantation

Among other factors, sophistication of immunosuppressive (IS) regimen accounts for the remarkable success attained in the short- and medium-term solid organ transplant (SOT) survival. The use of steroids, mycophenolate mofetil and calcineurin inhibitors (CNI) have led to annual renal graft survival rates exceeding 90% in the last six decades. On the other hand, attrition rates of the allograft beyond the first year have remained unchanged. In addition, there is a persistent high cardiovascular (CV) mortality rate among transplant recipients with functioning grafts. These shortcomings are in part due to the metabolic effects of steroids, CNI and sirolimus (SRL), all of which are implicated in hypertension, new onset diabetes after transplant (NODAT), and dyslipidemia. In a bid to reduce the required amount of harmful maintenance agents, T-cell-depleting antibodies are increasingly used for induction therapy. The downsides to their use are greater incidence of opportunistic viral infections and malignancy. On the other hand, inadequate immunosuppression causes recurrent rejection episodes and therefore early-onset chronic allograft dysfunction. In addition to the adverse metabolic effects of the steroid rescue needed in these settings, the generated proinflammatory milieu may promote accelerated atherosclerotic disorders, thus setting up a vicious cycle. The recent availability of newer agent, belatacept holds a promise in reducing the incidence of metabolic disorders and hopefully its long-term CV consequences. Although therapeutic drug monitoring as applied to CNI may be helpful, pharmacodynamic tools are needed to promote a customized selection of IS agents that offer the most benefit to an individual without jeopardizing the allograft survival.

Genotype-guided tacrolimus dosing in African-American kidney transplant recipients

Tacrolimus is dependent on CYP3A5 enzyme for metabolism. Expression of the CYP3A5 enzyme is controlled by several alleles including CYP3A5*1, CYP3A5*3, CYP3A5*6 and CYP3A5*7. African Americans (AAs) have on average higher tacrolimus dose requirements than Caucasians; however, some have requirements similar to Caucasians. Studies in AAs have primarily evaluated the CYP3A5*3 variant; however, there are other common nonfunctional variants in AAs (CYP3A5*6 and CYP3A5*7) that do not occur in Caucasians. These variants are associated with lower dose requirements and may explain why some AAs are metabolically similar to Caucasians. We created a tacrolimus clearance model in 354 AAs using a development and validation cohort. Time after transplant, steroid and antiviral use, age and CYP3A5*1, *3, *6 and *7 alleles were significant toward clearance. This study is the first to develop an AA-specific genotype-guided tacrolimus dosing model to personalize therapy.

Lack of a significant pharmacokinetic interaction between maraviroc and tacrolimus in allogeneic HSCT recipients

OBJECTIVES

Emerging data suggest that the combination of tacrolimus and the CCR5 antagonist maraviroc, both cytochrome P450-3A4 substrates, may be effective in preventing graft-versus-host disease in patients undergoing allogeneic HSCT. This study evaluated whether a pharmacokinetic interaction exists between these agents.

METHODS

The study included 36 allogeneic HSCT recipients who received maraviroc + tacrolimus and 43 recipients of tacrolimus alone. We used a difference-in-differences analysis to examine the change in the concentration/dose ratios of tacrolimus after the discontinuation of maraviroc. In addition, we analysed the concentrations and dose requirements of tacrolimus in the two groups.

RESULTS

There was no significant difference in tacrolimus concentration/dose ratios in patients receiving maraviroc + tacrolimus compared with tacrolimus alone. Upon discontinuation of maraviroc, the change in concentration/dose ratio was small and not significant relative to the control group, and the effect estimate was further attenuated after adjustment for confounders [-0.35 (ng/mL)/(mg/day); P = 0.46]. In addition, the change in mean tacrolimus dose after discontinuation of maraviroc was similar between the groups (0.12 mg/day; P = 0.56), as was the change in mean tacrolimus concentration (0.02 ng/mL; P = 0.97).

CONCLUSIONS

Our findings do not support a significant inhibitory effect of maraviroc on the metabolism of tacrolimus. These data demonstrate that this drug combination is safe and imply that the protective effect of maraviroc against graft-versus-host disease was not mediated through an increase in tacrolimus concentrations. These findings are important for the design of clinical trials that evaluate maraviroc in combination with cytochrome P450-3A4 substrates.