Racial differences in renal transplantation after immunosuppression with tacrolimus versus cyclosporine. FK506 Kidney Transplant Study Group

Heart Transplantation-Postoperative Considerations

Heart transplantation (HT) remains the best treatment of patients with severe heart failure who are deemed to be transplant candidates. The authors discuss postoperative management of the HT recipient by system, emphasizing areas where care might differ from other cardiac surgery patients. Working together, critical care physicians, heart transplant surgeons and cardiologists, advanced practice providers, pharmacists, transplant coordinators, nursing staff, physical therapists, occupational therapists, rehabilitation specialists, nutritionists, health psychologists, social workers, and the patient and their loved ones partner to increase the likelihood of a successful outcome.

GRWR Correlates with the Metabolism of Tacrolimus after Pediatric Living Donor Liver Transplantation According to Donor CYP3A5 Polymorphism

Objectives. Tacrolimus is characterized by high pharmacokinetic variability in combination with a narrow therapeutic range. However, influence of donor CYP3A5 genotype and graft-to-recipient body weight ratio (GRWR) on tacrolimus’ pharmacokinetics after pediatric living donor liver transplantation (LDLT) remains unclear. Methods. A total of 174 LDLT recipients (<6 y) were grouped according to donor CYP3A5 genotypes (nonexpressor (NEX) or expressor (EX)) and GRWR (<3.0% (SS, small-size) or ≥3.0% (LS, large-size)): SS/NEX ( $n=40$ ), SS/EX ( $n=38$ ), LS/NEX ( $n=48$ ), and LS/EX ( $n=48$ ). Pharmacokinetics of tacrolimus and clinical outcomes were analyzed. Results. The relationships between the concentration-dose ratio and donor CYP3A5 genotypes and graft size were examined 3, 7, 14, and 30 days after the transplantation. Tacrolimus C0 levels varied greatly among groups, although recipients started with the same initial dosage. LS/EX recipients had significantly lower C0 levels in comparison with those of other groups. The use of CYP3A5-EX-grafts and a greater GRWR both resulted in significantly higher TAC dose requirements and lower C/D ratios. However, the significance of GRWR no longer exists 3 months after transplantation. The multivariate generalized linear mixed model analysis showed that donor CYP3A5 genotypes ( $F=11.876$ ; $P=0.01$ ) and GRWR ( $F=4.631$ ; $P=0.033$ ) were independent impact factors for C/D ratios 3, 7, 14, and 30 days after transplantation. Donor CYP3A5-EX genotype was associated with significantly increasing risks of infectious complications and significantly lower Cylex ATP values. However, no significant difference was observed in acute rejections among 4 groups. Conclusions. Monitoring of C0 levels alone is not reliable to guide tacrolimus administration. Donor CYP3A5 and GRWR both significantly affect tacrolimus pharmacokinetics after pediatric LDLT. The use of Cylex ATP tests would be helpful to avoid overimmunosuppression.

Use of Machine Learning Consensus Clustering to Identify Distinct Subtypes of Black Kidney Transplant Recipients and Associated Outcomes

Importance

Among kidney transplant recipients, Black patients continue to have worse graft function and reduced patient and graft survival. Better understanding of different phenotypes and subgroups of Black kidney transplant recipients may help the transplant community to identify individualized strategies to improve outcomes among these vulnerable groups.

Objective

To cluster Black kidney transplant recipients in the US using an unsupervised machine learning approach.

Design, Setting, and Participants

This cohort study performed consensus cluster analysis based on recipient-, donor-, and transplant-related characteristics in Black kidney transplant recipients in the US from January 1, 2015, to December 31, 2019, in the Organ Procurement and Transplantation Network/United Network for Organ Sharing database. Each cluster's key characteristics were identified using the standardized mean difference, and subsequently the posttransplant outcomes were compared among the clusters. Data were analyzed from June 9 to July 17, 2021.

Exposure

Machine learning consensus clustering approach.

Main Outcomes and Measures

Death-censored graft failure, patient death within 3 years after kidney transplant, and allograft rejection within 1 year after kidney transplant.

Results

Consensus cluster analysis was performed for 22 687 Black kidney transplant recipients (mean [SD] age, 51.4 [12.6] years; 13 635 men [60%]), and 4 distinct clusters that best represented their clinical characteristics were identified. Cluster 1 was characterized by highly sensitized recipients of deceased donor kidney retransplants; cluster 2, by recipients of living donor kidney transplants with no or short prior dialysis; cluster 3, by young recipients with hypertension and without diabetes who received young deceased donor transplants with low kidney donor profile index scores; and cluster 4, by older recipients with diabetes who received kidneys from older donors with high kidney donor profile index scores and extended criteria donors. Cluster 2 had the most favorable outcomes in terms of death-censored graft failure, patient death, and allograft rejection. Compared with cluster 2, all other clusters had a higher risk of death-censored graft failure and death. Higher risk for rejection was found in clusters 1 and 3, but not cluster 4.

Conclusions and Relevance

In this cohort study using an unsupervised machine learning approach, the identification of clinically distinct clusters among Black kidney transplant recipients underscores the need for individualized care strategies to improve outcomes among vulnerable patient groups.

Race does not predict pancreas graft failure after pancreas transplantation in the Modern Era

BACKGROUND

African-American (AA) has historically been associated with inferior graft survival after pancreas transplantation. However, with the improvement of immunosuppression and surgical technique, we hypothesized that the racial disparity has been neutralized.

METHODS

We analyzed data from the Scientific Registry of Transplant Recipients (1989-2018). Using Kaplan-Meier estimation and Cox proportional hazards regression, we examined the influence of race on pancreatic graft survival.

RESULTS

Before 2009, AA recipients had a higher risk of pancreatic graft failure after adjusting for confounding factors (hazard ratio [HR]: 1.16, 95% confidence interval [CI]: 1.08-1.24), but the risks for Hispanic and Asian recipients were both comparable to their Caucasian counterparts. However, the risk of pancreatic graft failure in AA recipients dropped to 1% and was no longer significant since 2009 (HR: 1.01, 95%CI: 0.88-1.16). Interestingly, donor race showed similar results. Furthermore, the concordance statistic of the complete pancreas donor risk index (including donor race) was 0.582, whereas the concordance did not change when donor race was eliminated from the model.

CONCLUSIONS

AA and other races have shown similar pancreatic graft survival in the modern era. Furthermore, donor racial disparity also seems neutralized; thus, donor race should not be considered as an indicator of pancreatic donor quality. This article is protected by copyright. All rights reserved.

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.

Kidney transplant outcomes in minority populations: can we close the gap?

PURPOSE OF REVIEW

Health disparity in minority populations has been increasingly recognized over the last decade. The COVID-19 pandemic sheds a bright light on this very issue impressing upon the need for more research regarding healthcare in disparate populations. Although kidney transplantation remains the treatment of choice for end-stage renal disease management and longevity of life, access to transplantation remains a critical barrier in minority populations. The literature on disparity in access abounds but remains limited with regards to posttransplantation outcomes. The purpose of this review is to draw attention to existing research and literature in posttransplant outcomes and highlight the overall knowledge gap that persists in postkidney transplant care among disparate populations.

RECENT FINDINGS

The current review focuses on important paradigm shifts in the determinants of outcomes in posttransplantation care in minority populations. It emphasizes a departure from immune mediated causes to more salient health inequities and socioeconomic factors contributing to patient and graft survival which require further investigation.

SUMMARY

Despite increased awareness of health disparity in minority populations, outcomes data postkidney transplantation remains sparse. Critical to the future of kidney transplantation and improved healthcare coordination in minority populations will be a deeper understanding of contributing socio-economic variables in disparate outcomes.

Efficacy and Safety of Once-Daily LCP-Tacrolimus Versus Twice-Daily Immediate-Release Tacrolimus in Adult Hispanic Stable Kidney Transplant Recipients: Sub-Group Analysis from a Phase 3 Trial

BACKGROUND The pharmacokinetics and metabolism of tacrolimus, an immunosuppressant commonly used to prevent transplant rejection, can differ in specific subpopulations. This analysis examined treatment outcomes and safety of immediate-release tacrolimus (IR-Tac) and LCP-tacrolimus (LCPT) in stable Hispanic kidney transplant recipients. MATERIAL AND METHODS This was a post hoc analysis of clinical trial data from Hispanic adult stable kidney transplant recipients randomized to remain on IR-Tac or convert from IR-Tac to a reduced dose of LCPT (NCT00817206). Composite treatment failure was evaluated at 12 months. Estimated glomerular filtration rate and tacrolimus trough concentrations were evaluated over 12 months. RESULTS Fifty-five stable (LCPT n=26, IR-Tac n=29) kidney transplant recipients who self-identified as Hispanic or Latino were included in this analysis. Composite treatment failure occurred in 1 patient (4%) who converted to LCPT and 1 (3%) who remained on IR-Tac. The estimated glomerular filtration rate was stable over time and similar in the 2 treatment groups (P=0.08). Tacrolimus trough levels for both groups were similar over time in the 2 treatment groups (P=0.98). Treatment-emergent adverse events were similar in patients who converted to LCPT and in those who remained on IR-Tac. CONCLUSIONS Efficacy and safety were similar in Hispanic kidney transplant recipients who converted from IR-Tac to LCPT and in those remaining on IR-Tac.

Metabolic Consequences of Solid Organ Transplantation

Metabolic complications affect over 50% of solid organ transplant recipients. These include posttransplant diabetes, nonalcoholic fatty liver disease, dyslipidemia, and obesity. Preexisting metabolic disease is further exacerbated with immunosuppression and posttransplant weight gain. Patients transition from a state of cachexia induced by end-organ disease to a pro-anabolic state after transplant due to weight gain, sedentary lifestyle, and suboptimal dietary habits in the setting of immunosuppression. Specific immunosuppressants have different metabolic effects, although all the foundation/maintenance immunosuppressants (calcineurin inhibitors, mTOR inhibitors) increase the risk of metabolic disease. In this comprehensive review, we summarize the emerging knowledge of the molecular pathogenesis of these different metabolic complications, and the potential genetic contribution (recipient +/- donor) to these conditions. These metabolic complications impact both graft and patient survival, particularly increasing the risk of cardiovascular and cancer-associated mortality. The current evidence for prevention and therapeutic management of posttransplant metabolic conditions is provided while highlighting gaps for future avenues in translational research.

Beyond Single Nucleotide Polymorphisms: CYP3A5∗3∗6∗7 Composite and ABCB1 Haplotype Associations to Tacrolimus Pharmacokinetics in Black and White Renal Transplant Recipients

Interpatient variability in tacrolimus pharmacokinetics is attributed to metabolism by cytochrome P-450 3A5 (CYP3A5) isoenzymes and membrane transport by P-glycoprotein. Interpatient pharmacokinetic variability has been associated with genotypic variants for both CYP3A5 or ABCB1. Tacrolimus pharmacokinetics was investigated in 65 stable Black and Caucasian post-renal transplant patients by assessing the effects of multiple alleles in both CYP3A5 and ABCB1. A metabolic composite based upon the CYP3A5 polymorphisms: ^∗3(rs776746), ^∗6(10264272), and ^∗7(41303343), each independently responsible for loss of protein expression was used to classify patients as extensive, intermediate and poor metabolizers. In addition, the role of ABCB1 on tacrolimus pharmacokinetics was assessed using haplotype analysis encompassing the single nucleotide polymorphisms: 1236C > T (rs1128503), 2677G > T/A(rs2032582), and 3435C > T(rs1045642). Finally, a combined analysis using both CYP3A5 and ABCB1 polymorphisms was developed to assess their inter-related influence on tacrolimus pharmacokinetics. Extensive metabolizers identified as homozygous wild type at all three CYP3A5 loci were found in 7 Blacks and required twice the tacrolimus dose (5.6 ± 1.6 mg) compared to Poor metabolizers [2.5 ± 1.1 mg (P < 0.001)]; who were primarily Whites. These extensive metabolizers had 2-fold faster clearance (P < 0.001) with 50% lower AUC^∗ (P < 0.001) than Poor metabolizers. No differences in C_{12 h} were found due to therapeutic drug monitoring. The majority of blacks (81%) were classified as either Extensive or Intermediate Metabolizers requiring higher tacrolimus doses to accommodate the more rapid clearance. Blacks who were homozygous for one or more loss of function SNPS were associated with lower tacrolimus doses and slower clearance. These values are comparable to Whites, 82% of who were in the Poor metabolic composite group. The ABCB1 haplotype analysis detected significant associations of the wildtype 1236T-2677T-3435T haplotype to tacrolimus dose (P = 0.03), CL (P = 0.023), CL/LBW (P = 0.022), and AUC^∗ (P = 0.078). Finally, analysis combining CYP3A5 and ABCB1 genotypes indicated that the presence of the ABCB1 3435 T allele significantly reduced tacrolimus clearance for all three CPY3A5 metabolic composite groups. Genotypic associations of tacrolimus pharmacokinetics can be improved by using the novel composite CYP3A5^∗3^∗4^∗5 and ABCB1 haplotypes. Consideration of multiple alleles using CYP3A5 metabolic composites and drug transporter ABCB1 haplotypes provides a more comprehensive appraisal of genetic factors contributing to interpatient variability in tacrolimus pharmacokinetics among Whites and Blacks.

Tacrolimus troughs and genetic determinants of metabolism in kidney transplant recipients: A comparison of four ancestry groups

Tacrolimus trough and dose requirements vary dramatically between individuals of European and African American ancestry. These differences are less well described in other populations. We conducted an observational, prospective, multicenter study from which 2595 kidney transplant recipients of European, African, Native American, and Asian ancestry were studied for tacrolimus trough, doses, and genetic determinants of metabolism. We studied the well-known variants and conducted a CYP3A4/5 gene-wide analysis to identify new variants. Daily doses, and dose-normalized troughs were significantly different between the four groups (P < .001). CYP3A5*3 (rs776746) was associated with higher dose-normalized tacrolimus troughs in all groups but occurred at different allele frequencies and had differing effect sizes. The CYP3A5*6 (rs10264272) and *7 (rs413003343) variants were only present in African Americans. CYP3A4*22 (rs35599367) was not found in any of the Asian ancestry samples. We identified seven suggestive variants in the CYP3A4/5 genes associated with dose-normalized troughs in Native Americans (P = 1.1 × 10^-5 -8.8 × 10^-6 ) and one suggestive variant in Asian Americans (P = 5.6 × 10^-6 ). Tacrolimus daily doses and dose-normalized troughs vary significantly among different ancestry groups. We identified potential new variants important in Asians and Native Americans. Studies with larger populations should be conducted to assess the importance of the identified suggestive variants.

Pharmacist-Led, Technology-Assisted Study to Improve Medication Safety, Cardiovascular Risk Factor Control, and Racial Disparities in Kidney Transplant Recipients

Introduction

Health disparities in African-American (AA) kidney transplant recipients compared with non-AA recipients are well established. Cardiovascular disease (CVD) risk control is a significant mediator of this disparity.

Objective

To assess the efficacy of improved medication safety, CVD risk control, and racial disparities in kidney transplant recipients.

Methods

Prospective, pharmacist-led, technology-aided, 6-month interventional clinical trial. A total of 60 kidney recipients with diabetes and hypertension were enrolled. Patients had to be at least one-year post transplant with stable graft function. Primary outcome measured included hypertension, diabetes, and lipid control using intent-to-treat analyses, with differences assessed between AA and non-AA recipients.

Results

The participants mean age was 59 years, with 42% being female and 68% being AA. Overall, patients demonstrated improvements in blood pressure <140/90 mmHg (baseline 50% vs. end of study 68%, p=0.054) and hemoglobin A1c <7% (baseline 33% vs. end of study 47%, p=0.061). AAs demonstrated a significant reduction from baseline in systolic blood pressure (-0.86 mmHg per month, p=0.026), which was not evident in non-AAs (-0.13 mmHg per month, p=0.865). Mean HgbA1c decreased from baseline in the overall group (-0.12% per month, p=0.003), which was similar within AAs (-0.11% per month, p=0.004) and non-AAs (-0.14% per month, p=0.029). There were no changes in low-density lipoproteins, triglycerides, or high-density lipoproteins over the course of the study. Medication errors were significantly reduced and self-reported medication adherence significantly improved over the course of the study.

Conclusion

These results demonstrate the potential efficacy of a pharmacist-led, technology-aided, educational intervention in improving medication safety, diabetes, and hypertension and reducing racial disparities in AA kidney transplant recipients. (ClinicalTrials.gov NCT02763943).

Change in Mycophenolate and Tacrolimus Exposure by Transplant Vintage and Race

OBJECTIVES

Although both tacrolimus and mycophenolate have improved outcomes after kidney transplant, studies regarding effects of exposure on outcomes, specifically related to racial disparities, are sparse.

MATERIALS AND METHODS

In this 8-year longitudinal cohort study of adult kidney transplant recipients, mycophenolate and tacrolimus levels were compared across transplant vintage stratified by non-African Americans versus African Americans. Data were analyzed with standard univariate tests and multivariable regression models.

RESULTS

Our study included 1217 patients (transplanted from 2005-2013) who had tacrolimus and myco-phenolate exposure data, with follow-up through 2015 (53.7% were African Americans). Mean mycophenolate dose was 1672 ± 463 mg/day during the first 3 years posttransplant. Although transplant vintage did not appreciably impact mycophenolate dosing in non-African Americans (0.7 mg/day/y; P = .903), doses significantly decreased in African Americans across transplant vintage (-20.5 mg/day/y; P < .001). Rate of mycophenolate being held or discontinued based on transplant vintage significantly increased in African Americans but did not change in non-African Americans. At the beginning of the study, mean tacrolimus levels were lower in African Americans; however, levels then slightly decreased in non-African Americans (-0.03 ng/mL/y; P = .279) and slightly increased in African Americans (+0.03 ng/mL/y; P = .247), with similar levels by 2013. Higher tacrolimus levels were protective against rejection in African Americans only but were protective against death-censored graft loss in both race/ethnicity groups. Mycophenolate dosing had no appreciable impact on outcomes in African Americans, but higher mycophenolate dosing was a significant risk factor for death-censored graft loss in non-African Americans.

CONCLUSIONS

Tacrolimus and mycophenolate exposure levels have significantly changed over time and differed by race/ethnicity. In non-African Americans, those transplanted more recently tended to have lower tacrolimus but similar mycophenolate exposure. Although mycophenolate exposure in African Americans has recently decreased, tacrolimus has increased. Differences in outcomes likely reflect improved understanding of immunosuppressant tolerability by recipient race/ethnicity.

Urinary microbiome associated with chronic allograft dysfunction in kidney transplant recipients

BACKGROUND

We performed a study to identify differences in the urinary microbiome associated with chronic allograft dysfunction (CAD) and compared the urinary microbiome of male and female transplant recipients with CAD.

METHODS

This case-control study enrolled 67 patients within the Deterioration of Kidney Allograft Function (DeKAF) Genomics cohort at two transplant centers. CAD was defined as a greater than 25% rise in serum creatinine relative to a 3 month post-transplant baseline. Urine samples from patients with and without CAD were analyzed using 16S V4 bacterial ribosomal DNA sequences.

RESULTS

Corynebacterium was more prevalent in female and male patients with CAD compared to non-CAD female patients (P = 0.0005). A total 21 distinct Operational Taxonomic Unit (OTUs) were identified as significantly different when comparing CAD and non-CAD patients using Kruskal-Wallis (P < 0.01). A subset analysis of female patients with CAD compared to non-CAD females identified similar differentially abundant OTUs, including the genera Corynebacterium and Staphylococcus (Kruskal-Wallis; P = 0.01; P = 0.004, respectively). Male CAD vs female CAD analysis showed greater abundance of phylum Proteobacteria in males.

CONCLUSION

There were differences in the urinary microbiome when comparing female and male CAD patients with their female non-CAD counterparts and these differences persisted in the subset analysis limited to female patients only.

Randomized Controlled Trial Assessing the Impact of Tacrolimus Versus Cyclosporine on the Incidence of Posttransplant Diabetes Mellitus

INTRODUCTION

Despite the high incidence of posttransplant diabetes mellitus (PTDM) among high-risk recipients, no studies have investigated its prevention by immunosuppression optimization.

METHODS

We conducted an open-label, multicenter, randomized trial testing whether a tacrolimus-based immunosuppression and rapid steroid withdrawal (SW) within 1 week (Tac-SW) or cyclosporine A (CsA) with steroid minimization (SM) (CsA-SM), decreased the incidence of PTDM compared with tacrolimus with SM (Tac-SM). All arms received basiliximab and mycophenolate mofetil. High risk was defined by age >60 or >45 years plus metabolic criteria based on body mass index, triglycerides, and high-density lipoprotein-cholesterol levels. The primary endpoint was the incidence of PTDM after 12 months.

RESULTS

The study comprised 128 de novo renal transplant recipients without pretransplant diabetes (Tac-SW: 44, Tac-SM: 42, CsA-SM: 42). The 1-year incidence of PTDM in each arm was 37.8% for Tac-SW, 25.7% for Tac-SM, and 9.7% for CsA-SM (relative risk [RR] Tac-SW vs. CsA-SM 3.9 [1.2-12.4; P = 0.01]; RR Tac-SM vs. CsA-SM 2.7 [0.8-8.9; P = 0.1]). Antidiabetic therapy was required less commonly in the CsA-SM arm (P = 0.06); however, acute rejection rate was higher in CsA-SM arm (Tac-SW 11.4%, Tac-SM 4.8%, and CsA-SM 21.4% of patients; cumulative incidence P = 0.04). Graft and patient survival, and graft function were similar among arms.

CONCLUSION

In high-risk patients, tacrolimus-based immunosuppression with SM provides the best balance between PTDM and acute rejection incidence.

Tacrolimus Population Pharmacokinetics and Multiple CYP3A5 Genotypes in Black and White Renal Transplant Recipients

Tacrolimus exhibits inter-patient pharmacokinetic variability attributed to CYP3A5 isoenzymes and the efflux transporter, P-glycoprotein. Most black renal transplant recipients require higher tacrolimus doses compared to whites to achieve similar troughs when race-adjusted recommendations are used. An established guideline provides tacrolimus genotype dosing recommendations based on CYP3A5*1(W/T) and loss of protein function variants: CYP3A5*3 (rs776746), CYP3A5*6 (rs10264272), CYP3A5*7 (rs41303343) and may provide more comprehensive race-adjusted dosing recommendations. Our objective was to develop a tacrolimus population pharmacokinetic model evaluating demographic, clinical, and genomic factors in stable black and white renal transplant recipients. A secondary objective investigated race-based tacrolimus regimens and genotype-specific dosing. Sixty-seven recipients receiving oral tacrolimus and mycophenolic acid ≥6 months completed a 12-hour pharmacokinetic study. CYP3A5*3,*6,*7 and ABCB1 1236C>T, 2677G>T/A, 3435C>T polymorphisms were characterized. Patients were classified as extensive, intermediate, and poor metabolizers using a novel CYP3A5*3*6*7 metabolic composite. Modeling and simulation was performed with computer software (NONMEM 7.3, ICON Development Solutions; Ellicott City, Maryland). A 2-compartment model with first-order elimination and absorption with lag time best described the data. The CYP3A5*3*6*7 metabolic composite was significantly associated with tacrolimus clearance (P value < .05), which was faster in extensive (mean: 45.0 L/hr) and intermediate (29.5 L/hr) metabolizers than poor metabolizers (19.8 L/hr). Simulations support CYP3A5*3*6*7 genotype-based tacrolimus dosing to enhance general race-adjusted regimens, with dose increases of 1.5-fold and 2-fold, respectively, in intermediate and extensive metabolizers for comparable exposures to poor metabolizers. This model offers a novel approach to determine tacrolimus dosing adjustments that maintain comparable therapeutic exposure between black and white recipients with different CYP3A5 genotypes.

Improving Medication Safety and Cardiovascular Risk Factor Control to Mitigate Disparities in African-American Kidney Transplant Recipients: Design and Methods

There is a lack of data analyzing the influence of cardiovascular disease (CVD) risk factor control on graft survival disparities in African-American kidney transplant recipients. Studies in the general population indicate that CVD risk factor control is poor in African-Americans, leading to higher rates of renal failure and major acute cardiovascular events. However, with the exception of hypertension, there is no data demonstrating similar results within transplant recipients. Recent analyses conducted by our investigator group indicate that CVD risk factors, especially diabetes, are poorly controlled in African-American recipients, which likely impacts graft loss. This study protocol describes a prospective interventional clinical trial with the goal of demonstrating improved medication safety and CVD risk factor control in adult solitary kidney transplant recipients at least one-year post-transplant with a functioning graft. This is a prospective, interventional, 6-month, pharmacist-led and technology enabled study in adult kidney transplant recipients with the goal of improving CVD risk factor outcomes by improving medication safety and patient self-efficacy. This papers describes the issues related to racial disparities in transplant, the details of this intervention and how we expect this intervention to improve CVD risk factor control in kidney transplant recipients, particularly within African-Americans.

Transplant Center Variability in Disparities for African-American Kidney Transplant Recipients

Background

Disparities research has traditionally focused on patient-level variables to ascertain predominant risk factors driving differences in outcomes for African-American (AA) kidney transplant recipients. Our objectives were to determine the magnitude and impact of transplant center variability for graft outcome disparities.

Material/Methods

This was a retrospective cohort study analyzing 25 years of U.S. national transplant registry data at both the patient and center levels using univariate descriptive statistics and multivariable modeling.

Results

A total of 257,024 recipients from 191 centers were analyzed; AAs represented 31.1% of recipients. After adjusting for baseline characteristics, AAs had 42% higher risk of graft loss (aHR 1.42, 95% CI 1.39 to 1.45; p<0.001). Center variability for graft outcome disparities in AAs was significant (race*center interaction term p<0.05), with the aHRs ranging from 0.5 to 4.9; 46% of centers demonstrated a non-statistically significant disparity (aHR p>0.05) and 25% of centers had a large AA disparity (aHR >1.75). In a more recent transplant time period (2000–14), overall racial disparities decreased but center-level disparities increased in variability. Center-level factors significantly associated with increasing disparity included higher acute rejection rates, fewer transplants per year, longer length of stay, lower use of calcineurin inhibitors (CNI), and lower living donor rates.

Conclusions

There is evidence of significant center-level variability in graft outcome disparities for AA kidney recipients. Further, there appears to be a number of center-level factors associated with this variability, including acute rejection rates, CNI use, number of transplants per year, and, in recent years, low living donor rates.

Tacrolimus Trough Concentration Variability and Disparities in African American Kidney Transplantation

BACKGROUND

Low tacrolimus concentrations have been associated with higher risk of acute rejection, particularly within African American (AA) kidney transplant recipients; little is known about intrapatient tacrolimus variabilities impact on racial disparities.

METHODS

Ten year, single-center, longitudinal cohort study of kidney recipients. Intrapatient tacrolimus variability was assessed using the coefficient of variation (CV) measured between 1 month posttransplant and the clinical event, with a comparable period assessed in those without events. Pediatrics, nontacrolimus/mycophenolate regimens, and nonrenal transplants were excluded. Multivariable Cox regression models were used to analyze data.

RESULTS

One thousand four hundred eleven recipients were included (54.4% AA) with 39 521 concentrations used to assess intrapatient tacrolimus CV. Overall, intrapatient tacrolimus CV was higher in AAs versus non-AAs (39.9 ± 19.8 % vs 34.8 ± 15.8% P < 0.001). Tacrolimus variability was a significant risk factor for deleterious clinical outcomes. A 10% increase in tacrolimus CV augmented the risk of acute rejection by 20% (adjusted hazard ratio, 1.20, 1.13-1.28; P < 0.001) and the risk of graft loss by 30% (adjusted hazard ratio, 1.30, 1.23-1.37; P < 0.001), with significant effect modification by race for acute rejection, but not graft loss. High tacrolimus variability (CV >40%) was a significant explanatory variable for disparities in AAs; the crude relative risk of acute rejection in AAs was reduced by 46% when including tacrolimus variability in modeling and reduced by 40% for graft loss.

CONCLUSIONS

These data demonstrate that intrapatient tacrolimus variability is strongly associated with acute rejection in AAs and graft loss in all patients. Tacrolimus variability is a significant explanatory variable for disparities in AA recipients.

Longitudinal Pharmacokinetics of Tacrolimus in Elderly Compared With Younger Recipients in the First 6 Months After Renal Transplantation

BACKGROUND

Elderly (Eld) (≥60 years) recipients are receiving renal transplants more frequently. The pharmacokinetics (PK) studies of immunosuppressive drugs in healthy volunteers, rarely, include old patients.

METHODS

We studied 208 12-hour tacrolimus (TAC) PK (0, 20, 40, 60, 90, 120, 180, 240, 360, 480, 600, 720 min) in 44 Eld (65 ± 3 years) and compared the results with 31 younger controls (Ctrl) (35 ± 6 years) recipients, taking oral TAC/mycophenolate sodium (MPS)/prednisone, at 4 different timepoints: PK1 (8 ± 2 days; n = 72), PK2 (31 ± 4 days; n = 61), PK3 (63 ± 6 days; n = 44), and PK4 (185 ± 10 days; n = 31). Tacrolimus PK was measured by ultraperformance liquid chromatography coupled to a mass spectrometer repetition and noncompartmental PKs were analyzed using Phoenix WinNonlin.

RESULTS

Mean TAC dose was lower in the Eld group than in Ctrl ones throughout timepoints either by total daily dose or adjusted (Adj) per body weight. Mean TAC trough level (Cmin), used to adjust daily dose, was not different between the 2 groups in all timepoints. AdjCmax and AdjTAC-area under the curve at dosing interval were both higher in the Eld compared to the Ctrl group in PKs1, 3, and 4. Estimated total body clearance normalized by dose and weight was lower in the Eld group compared with the Ctrl in all PKs and statistically lower at PKs 1 and 3. Similar to younger recipients TAC trough level has also a high correlation (R = 0.76) with area under the curve at dosing interval.

CONCLUSIONS

These data indicate that Eld recipients have a lower TAC clearance and therefore need a lower TAC dose than younger recipients.

Personalized Medicine: New Perspectives for the Diagnosis and the Treatment of Renal Diseases

The prevalence of renal diseases is rising and reaching 5-15% of the adult population. Renal damage is associated with disturbances of body homeostasis and the loss of equilibrium between exogenous and endogenous elements including drugs and metabolites. Studies indicate that renal diseases are influenced not only by environmental but also by genetic factors. In some cases the disease is caused by mutation in a single gene and at that time severity depends on the presence of one or two mutated alleles. In other cases, renal disease is associated with the presence of alteration within a gene or genes, but environmental factors are also necessary for the development of disease. Therefore, it seems that the analysis of genetic aspects should be a natural component of clinical and experimental studies. The goal of personalized medicine is to determine the right drug, for the right patient, at the right time. Whole-genome examinations may help to change the approach to the disease and the patient resulting in the creation of "personalized medicine" with new diagnostic and treatment strategies designed on the basis of genetic background of each individual. The identification of high-risk patients in pharmacogenomics analyses will help to avoid many unwarranted side effects while optimizing treatment efficacy for individual patients. Personalized therapies for kidney diseases are still at the preliminary stage mainly due to high costs of such analyses and the complex nature of human genome. This review will focus on several areas of interest: renal disease pathogenesis, diagnosis, treatment, rate of progression and the prediction of prognosis.

Tacrolimus dose requirement based on the CYP3A5 genotype in renal transplant patients

Tacrolimus (FK506) and cyclosporine A (CsA) are widely used to protect graft function after renal transplantation. The aim of the present study is to determine whether the single nucleotide polymorphism of CYP3A5 is a predictive index of FK506 dose requirement, and also the selection yardstick of FK506 or CsA treatment.We tested archival peripheral blood of 218 kidney recipients for CYP3A5 genotyping with PCR-SSP. Meanwhile, the dose of FK506 and CsA was recorded, blood concentration of the drugs was measured, and graft outcome was monitored.These results indicate that CYP3A5*AA/AG carriers need higher FK506 dose than CYP3A5*GG homozygote to achieve the target blood concentration. For CYP3A5*GG carriers, taking FK506 or CsA are both advisable. CYP3A5*AA/AG carriers preferred to CsA treatment depending on the graft outcomes and drug costs. CYP3A5 genotyping is a new approach to detecting FK506 dose requirement and a predictive index for the FK506 or CsA treatment selection in kidney recipients.

Immune function monitoring in lung transplantation using adenosine triphosphate production: time trends and relationship to postoperative infection

PURPOSE

The ImmuKnow (IK) assay is a comprehensive immune function test that involves measuring adenosine triphosphate produced by the cluster of differentiation 4+ T lymphocytes in peripheral blood. The aim of this study was to analyze the time trends of IK values and assess the relationship between IK values and infections in lung transplants.

METHODS

We prospectively collected 178 blood samples from 22 deceased-donor lung transplant (DDLT) recipients and 17 living-donor lobar lung transplant (LDLLT) recipients. A surveillance IK assay was performed postoperatively, then after 1 week and 1, 3, 6, and 12 months.

RESULTS

Time trends of IK values in stable recipients peaked 1 week after DDLT (477 ± 247 ATP ng/ml), and 1 month after LDLLT (433 ± 134 ng/ml), followed by a gradual decline over 1 year. The mean IK values in infections were significantly lower than those in the stable state (119 vs 312 ATP ng/ml, p = 0.0002).

CONCLUSIONS

IK values increased sharply after lung transplantation and then decreased gradually over time in the first year, suggesting a natural history of immune function. IK values were also significantly reduced during infections. These results may provide new insights into the utility of immune monitoring after lung transplantation.

Twenty years of evolving trends in racial disparities for adult kidney transplant recipients

Disparities in outcomes for African American (AA) kidney transplant recipients have persisted for 40 years without a comprehensive analysis of evolving trends in the risks associated with this disparity. Here we analyzed U.S. transplant registry data, which included adult Caucasian or AA solitary kidney recipients undergoing transplantation between 1990 and 2009 comprising 202,085 transplantations. During this 20-year period, the estimated rate of 5-year graft loss decreased from 27.6% to 12.8%. Notable trends in baseline characteristics that significantly differed by race over time included the following: increased prevalence of diabetes from 2001 to 2009 in AAs (5-year slope difference: 3.4%), longer time on the waiting list (76.5 more days per 5 years in AAs), fewer living donors in AAs from 2003 to 2009 (5-year slope difference: -3.36%), more circulatory death donors in AAs from 2000-09 (5-year slope difference: 1.78%), and a slower decline in delayed graft function in AAs (5-year slope difference: 0.85%). The absolute risk difference between AAs and Caucasians for 5-year graft loss significantly declined over time (-0.92% decrease per 5 years), whereas the relative risk difference actually significantly increased (3.4% increase per 5 years). These results provide a mixed picture of both promising and concerning trends in disparities for AA kidney transplant recipients. Thus, although the disparity for graft loss has significantly improved, equity is still far off, and other disparities, including living donation rates and delayed graft function rates, have widened during this time.

Race, Calcineurin Inhibitor Exposure, and Renal Function After Solid Organ Transplantation

BACKGROUND

Calcineurin-inhibitor (CNI)-induced nephrotoxicity frequently complicates transplantation. African-Americans are at a greater risk of renal failure than the general population. We investigated whether race was an effect modifier of the relationship between CNI exposure and kidney function after nonrenal solid organ transplantation.

METHODS

This is a retrospective cohort study of 1609 patients who underwent initial nonrenal solid organ transplantation between January 2000 and June 2012. A central repository administrative database was queried electronically for demographics, comorbidities, and serial levels of tacrolimus, cyclosporine, and serum creatinine. Predictors of interest were total drug exposure of tacrolimus and cyclosporine (area under the concentration-time curve) and self-reported race. The outcome of interest was cumulative change in estimated glomerular filtration rate (GFR).

RESULTS

There were 1109 patients treated with tacrolimus (271 African-Americans) and 500 patients treated with cyclosporine (113 African Americans). A decline in GFR over time was seen with total tacrolimus exposure (-1.3 mL/min/1.73 m(2) for every 5 ng/mL·year increase in tacrolimus) and total cyclosporine exposure (-1.1 mL/min/1.73 m(2) for every 50 ng/mL·year increase in cyclosporine). However, total CNI exposure effect on estimated GFR changes did not vary by race (P interaction was 0.9 for tacrolimus and 0.6 for cyclosporine).

CONCLUSIONS

Total CNI exposure is associated with worsening kidney function among patients with nonrenal solid organ transplantation. However, African-American patients are not more vulnerable to chronic CNI-induced nephrotoxicity when compared to white patients.

Impact of Cardiovascular Risk Factors on Graft Outcome Disparities in Black Kidney Transplant Recipients

Although outcome inequalities for non-Hispanic black (NHB) kidney transplant recipients are well documented, there is paucity in data assessing the impact of cardiovascular disease (CVD) risk factors on this disparity in kidney transplantation. This was a longitudinal study of a national cohort of veteran kidney recipients transplanted between January 2001 and December 2007. Data included baseline characteristics acquired through the United States Renal Data System linked to detailed clinical follow-up information acquired through the Veterans Affairs electronic health records. Analyses were conducted using sequential multivariable modeling (Cox regression), incorporating blocks of variables into iterative nested models; 3139 patients were included (2095 non-Hispanic whites [66.7%] and 1044 NHBs [33.3%]). NHBs had a higher prevalence of hypertension (100% versus 99%; P<0.01) and post-transplant diabetes mellitus (59% versus 53%; P<0.01) with reduced control of hypertension (blood pressure <140/90 60% versus 69%; P<0.01), diabetes mellitus (A1c <7%, 35% versus 47%; P<0.01), and low-density lipoprotein (<100 mg/dL, 55% versus 61%; P<0.01). Adherence to medications used to manage CVD risk was significantly lower in NHBs. In the fully adjusted models, the independent risk of graft loss in NHBs was substantially reduced (unadjusted hazard ratio, 2.00 versus adjusted hazard ratio, 1.49). CVD risk factors and control reduced the influence of NHB race by 9% to 18%. Similar trends were noted for mortality, and estimates were robust across in sensitivity analyses. These results demonstrate that NHB kidney transplant recipients have significantly higher rates of CVD risk factors and reduced CVD risk control. These issues are likely partly related to medication nonadherence and meaningfully contribute to racial disparities for graft outcomes.

LCPT once-daily extended-release tacrolimus tablets versus twice-daily capsules: a pooled analysis of two phase 3 trials in important de novo and stable kidney transplant recipient subgroups

African-American and elderly kidney transplant recipients (KTR) have increased risk for poor clinical outcomes post-transplant. Management of immunosuppression may be challenging in these patients and contribute to worse outcomes. A novel once-daily formulation of tacrolimus (LCPT) has demonstrated noninferiority, similar safety, improved bioavailability, a consistent concentration time profile, and less peak and peak-trough fluctuations vs. tacrolimus twice-daily (Tac BID). This pooled analysis of two phase 3 randomized, controlled trials, including 861 (LCPT N = 428; Tac BID N = 433; 38% of patients were stable KTR, and 62% were de novo KTR) patients, examined the efficacy of LCPT in KTR subgroups (blacks, females, and age ≥65). Overall, treatment failure [death, graft failure, centrally read biopsy-proven acute rejection (BPAR), or lost to follow-up] at 12 months was as follows: LCPT: 11.9%, BID Tac: 13.4% [-1.48% (-5.95%, 2.99%)]. BPAR rates were as follows: LCPT: 8.2%, Tac BID: 9.5% [-1.29% (-5.14%, 2.55%)]. Numerically, fewer treatment failure events with LCPT were found in the majority of subgroups, with significantly less treatment failure associated with LCPT among black KTR [-13.82% (-27.22%, -0.31%)] and KTR ≥65 [-13.46% (-25.27%, -0.78%)]. This pooled analysis suggests numerically lower efficacy failure rates associated with LCPT among high-risk subgroups, in particular black KTR and KTR ≥65 years old.

Post-Transplant Diabetes Mellitus: Causes, Treatment, and Impact on Outcomes

Post-transplant diabetes mellitus (PTDM) is a frequent consequence of solid organ transplantation. PTDM has been associated with greater mortality and increased infections in different transplant groups using different diagnostic criteria. An international consensus panel recommended a consistent set of guidelines in 2003 based on American Diabetes Association glucose criteria but did not exclude the immediate post-transplant hospitalization when many patients receive large doses of corticosteroids. Greater glucose monitoring during all hospitalizations has revealed significant glucose intolerance in the majority of recipients immediately after transplant. As a result, the international consensus panel reviewed its earlier guidelines and recommended delaying screening and diagnosis of PTDM until the recipient is on stable doses of immunosuppression after discharge from initial transplant hospitalization. The group cautioned that whereas hemoglobin A1C has been adopted as a diagnostic criterion by many, it is not reliable as the sole diabetes screening method during the first year after transplant. Risk factors for PTDM include many of the immunosuppressant medications themselves as well as those for type 2 diabetes. The provider managing diabetes and associated dyslipidemia and hypertension after transplant must be careful of the greater risk for drug-drug interactions and infections with immunosuppressant medications. Treatment goals and therapies must consider the greater risk for fluctuating and reduced kidney function, which can cause hypoglycemia. Research is actively focused on strategies to prevent PTDM, but until strategies are found, it is imperative that immunosuppression regimens are chosen based on their evidence to prolong graft survival, not to avoid PTDM.

African-American race modifies the influence of tacrolimus concentrations on acute rejection and toxicity in kidney transplant recipients

STUDY OBJECTIVE

To determine the effect of tacrolimus trough concentrations on clinical outcomes in kidney transplantation, while assessing if African-American (AA) race modifies these associations.

DESIGN

Retrospective longitudinal cohort study of solitary adult kidney transplants.

SETTING

Large tertiary care transplant center.

PATIENTS

Adult solitary kidney transplant recipients (n=1078) who were AA (n=567) or non-AA (n=511).

EXPOSURE

Mean and regressed slope of tacrolimus trough concentrations. Subtherapeutic concentrations were lower than 8 ng/ml.

MEASUREMENTS AND MAIN RESULTS

AA patients were 1.7 times less likely than non-AA patients to achieve therapeutic tacrolimus concentrations (8 ng/ml or higher) during the first year after kidney transplant (35% vs 21%, respectively, p<0.001). AAs not achieving therapeutic concentrations were 2.4 times more likely to have acute cellular rejection (ACR) as compared with AAs achieving therapeutic concentrations (20.8% vs 8.5%, respectively, p<0.01) and 2.5 times more likely to have antibody-mediated rejection (AMR; 8.9% vs 3.6%, respectively, p<0.01). Rates of ACR (8.3% vs 6.7%) and AMR (2.0% vs 0.9% p=0.131) were similar in non-AAs compared across tacrolimus concentration groups. Multivariate modeling confirmed these findings and demonstrated that AAs with low tacrolimus exposure experienced a mild protective effect for the development of interstitial fibrosis/tubular atrophy (IF/TA; hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.47-1.32) with the opposite demonstrated in non-AAs (HR 2.2, 95% CI 0.90-5.1).

CONCLUSION

In contradistinction to non-AAs, AAs who achieve therapeutic tacrolimus concentrations have substantially lower acute rejection rates but are at risk of developing IF/TA. These findings may reflect modifiable time-dependent racial differences in the concentration-effect relationship of tacrolimus. Achievement of therapeutic tacrolimus trough concentrations, potentially through genotyping and more aggressive dosing and monitoring, is essential to minimize the risk of acute rejection in AA kidney transplant recipients.

Comparison of longer-term outcomes after kidney transplantation between Hispanic and non-Hispanic whites in the United States

Little is known about the longer-term kidney transplant outcomes in the rapidly growing Hispanic population. Using the United States Renal Data System, we identified 105 250 Caucasian patients who received a first kidney transplant between January 1, 1996 and December 31, 2010. We tested for differences between Hispanic and non-Hispanic patients in the outcomes of (1) mortality, (2) all-cause graft failure, and (3) graft failure excluding death with a functioning graft. We used Cox regression to estimate (with 95% confidence intervals) multivariable-adjusted cause-specific hazard ratios (aHRCS ) for mortality and all-cause graft failure and subdistribution hazard ratios (aHRSD ) accounting for death as a competing risk for graft failure excluding death with a functioning graft. Both mortality [aHRCS  = 0.69 (0.65-0.73)] and all-cause graft failure [aHRCS  = 0.79 (0.75-0.83)] were lower in Hispanics. The association between Hispanic ethnicity and graft failure excluding death was modified by age (p < 0.003). Compared with non-Hispanic whites, graft failure excluding death with a functioning graft did not differ in Hispanics aged 18-39 years [aHRSD  = 0.96 (0.89-1.05)] or aged 40-59 years [aHRSD  = 1.08 (1.00-1.16)], but was 13% lower in those aged ≥60 years [aHRSD  = 0.87 (0.78-0.98)]. In conclusion, once accounting for differences in overall survival, better graft survival was found in older Hispanic patients, but among not those aged <60 years.

African American renal transplant recipients (RTR) require higher tacrolimus doses to achieve target levels compared to white RTR: does clotrimazole help?

The number of African Americans (AAs) on the kidney waiting list is increasing in the United States. Several studies showed that AAs are at higher risk for rejection and graft loss. Because of genetic polymorphisms, AAs may metabolize calcineurin inhibitors faster than Caucasian (C) individuals. The goal of this study is to evaluate the tacrolimus (TAC) dose required to reach therapeutic levels and to assess the impact of clotrimazole on TAC metabolism in AAs compared to C patients. One hundred forty-two AA renal transplant recipients (RTRs) were compared to 309 C RTRs. Demographics were similar in both groups. Induction therapy and maintenance immunosuppression were similar in both groups and included TAC, mycophenolate acid (MPA), and steroids. The goal in all RTRs was to maintain a 12-hour trough level of 10 to 15 ng/mL in the first 3 months, 8 to 10 ng/mL for the first year, and 5 to 8 ng/mL thereafter. To achieve these levels, AA RTRs require a significantly higher dosage of TAC compared to C patients (5.9 ± 2.9 vs 3.6 ± 2 mg/d, respectively, P < .0001). By multivariate analysis, TAC dose requirements were not affected by age, gender, MPA or prednisone dose, diabetes, and renal function. Adding clotrimazole (CTM) to the RTR regimen significantly reduced the TAC dose requirements in all RTRs. When CTM was used, the TAC dose requirement was not statistically significantly different between AA and C patients (2.6 ± 1.2 mg/d vs 1.8 ± 1.5 mg/d, P = .07). We conclude that AAs required a higher TAC dose to reach the desired trough level in RTRs compared to C RTRs. The use of CTM eliminates the need for higher doses of TAC in AA RTRs. Thus, CTM may aid AA RTRs in achieving therapeutic TAC levels while reducing drug costs.

Significant racial differences in the key factors associated with early graft loss in kidney transplant recipients

BACKGROUND

There is continued and significant debate regarding the salient etiologies associated with graft loss and racial disparities in kidney transplant recipients.

METHODS

This was a longitudinal cohort study of all adult kidney transplant recipients, comparing patients with early graft loss (<5 years) to those with graft longevity (surviving graft with at least 5 years of follow-up) across racial cohorts [African-American (AA) and non-AA] to discern risk factors.

RESULTS

524 patients were included, 55% AA, 151 with early graft loss (29%) and 373 with graft longevity (71%). Consistent within both races, early graft loss was significantly associated with disability income [adjusted odds ratio (AOR) 2.2, 95% CI 1.1-4.5], Kidney Donor Risk Index (AOR 3.2, 1.4-7.5), rehospitalization (AOR 2.1, 1.0-4.4) and acute rejection (AOR 4.4, 1.7-11.6). Unique risk factors in AAs included Medicare-only insurance (AOR 8.0, 2.3-28) and BK infection (AOR 5.6, 1.3-25). Unique protective factors in AAs included cardiovascular risk factor control: AAs with a mean systolic blood pressure <150 mm Hg had 80% lower risk of early graft loss (AOR 0.2, 0.1-0.7), while low-density lipoprotein <100 mg/dl (AOR 0.4, 0.2-0.8), triglycerides <150 mg/dl (AOR 0.4, 0.2-1.0) and hemoglobin A1C <7% (AOR 0.2, 0.1-0.6) were also protective against early graft loss in AA, but not in non-AA recipients.

CONCLUSIONS

AA recipients have a number of unique risk factors for early graft loss, suggesting that controlling cardiovascular comorbidities may be an important mechanism to reduce racial disparities in kidney transplantation.

Concomitant proton pump inhibitors with mycophenolate mofetil and the risk of rejection in kidney transplant recipients

BACKGROUND

Recent pharmacokinetic studies have demonstrated that proton pump inhibitors (PPI) reduce exposure of mycophenolic acid. However, the clinical significance of this drug-drug interaction on transplantation outcomes has not been determined.

METHODS

This was a retrospective cohort study in kidney transplant recipients who were prescribed rabbit antithymocyte globulin, calcineurin inhibitor, mycophenolate mofetil, and steroids. We evaluated the impact of PPI use on the 1-year rates of biopsy-proven acute rejection (BPAR).

RESULTS

Two hundred thirteen patients who were prescribed PPI were compared with 384 patients who were on standard acid-suppressive therapy with ranitidine. BPAR occurred in similar rates in both groups (15% vs. 12%; P=0.31). In a multivariable analysis, black race was associated with a higher risk of rejection (risk ratio [RR], 2.38; 95% confidence interval [CI], 1.41-4.03). While controlling for rejection risk factors, PPI exposure was associated with an increased risk of rejection in black patients (RR, 1.93; 95% CI, 1.18-3.16) but not in non-black patients (RR, 0.54; 95% CI, 0.19-1.49). At 1 year, BPAR type, BPAR grade, patient and graft survival, graft function, and time to BPAR were not associated with PPI exposure.

CONCLUSION

In this retrospective study, PPI use in the first transplant year was associated with an increased risk for BPAR in black patients but not in non-black patients. It is possible that a reduction in mycophenolic acid exposure contributed to the increased risk.

Long-term outcomes in African American kidney transplant recipients under contemporary immunosuppression: a four-yr analysis of the Mycophenolic acid Observational REnal transplant (MORE) study

Mycophenolic acid Observational REnal transplant (MORE) was a prospective, observational study of de novo kidney transplant patients receiving mycophenolic acid (MPA). Four-yr data on 904 patients receiving tacrolimus and enteric-coated mycophenolate sodium (EC-MPS) or mycophenolate mofetil (MMF) were analyzed to evaluate immunosuppression and graft outcomes in African American (AA, n = 218) vs. non-AA (n = 686) patients. Mean tacrolimus dose was higher in AA vs. non-AA patients but mean tacrolimus trough concentration was similar. Use of the recommended MPA dose in AA patients decreased from 78.9% at baseline to 33.1% at year 3. More AA patients received the recommended MPA dose with EC-MPS than MMF at month 6 (56.2% vs. 35.7%, p = 0.016) and month 36 (46.6% vs. 16.7%, p = 0.029), with no safety penalty. Significantly, more AA patients received corticosteroids than non-AA patients. Biopsy-proven acute rejection was higher in AA vs. non-AA patients (18.9% vs. 10.7%, p = 0.003), as was graft loss (10.9% vs. 4.4%, p = 0.003); differences were confirmed by Cox regression analysis. Patient survival was similar. Estimated GFR was comparable in AA vs. non-AA patients. Kidney allograft survival remains lower for AA vs. non-AA recipients even under the current standard of care.

Renal allograft outcomes following early corticosteroid withdrawal in Hispanic transplant recipients

BACKGROUND

Renal transplant outcomes in Hispanics have been conflicting regarding acute rejection (AR) and allograft survival. Additionally, the feasibility of early corticosteroid withdrawal (ECW) regimens among Hispanics has not been adequately addressed. The purpose of this study is to report outcomes following ECW among Hispanic renal transplant recipients.

METHODS

We retrospectively reviewed 498 consecutive renal transplants performed at our institution between July 2005 and October 2007, including 73 Hispanic and 146 white recipients who had ECW (median follow-up 49 months). Demographics, transplant data, and outcomes of Hispanic and white recipients (WR) were analyzed.

RESULTS

Hispanics had a higher incidence of diabetes mellitus and hypertension (p = 0.007), a higher proportion of blood type O (p = 0.006), and a higher serum panel reactive antibody at the time of transplantation (p = 0.02) compared with WR. Additionally, Hispanics were on dialysis longer than WR prior to transplantation (p = 0.03). Nevertheless, the incidence of AR, patient, and graft survival rates was similar (p > 0.05) between Hispanics and WR. Ethnicity was not an independent predictor of inferior patient and graft outcomes in multivariate analyses.

CONCLUSION

Our single-center experience indicates that ECW can be performed in Hispanic renal transplant recipients, with patient and allograft outcomes comparable with those observed in WR.

Genetic differences in Native Americans and tacrolimus dosing after kidney transplantation

Tacrolimus pharmacokinetics vary due to single nucleotide polymorphisms (SNPs) in metabolizing enzymes and membrane transporters that alter drug elimination. Clinically we observed that Native Americans require lower dosages of tacrolimus to attain trough levels similar to Caucasians. We previously demonstrated that Native Americans have decreased oral clearance of tacrolimus, suggesting that Native Americans may have more variant SNPs and, therefore, altered tacrolimus pharmacokinetic parameters. We conducted 12-hour pharmacokinetic studies on 24 adult Native American kidney transplant recipients on stable doses of tacrolimus for at least 1 month posttransplantation. Twenty-four Caucasian kidney transplant recipients were compared as controls. SNPs encoding the genes for the enzymes (CYP3A4, CYP3A5) and transporters (ABCB1, BCRP, and MRP1) were typed using TaqMan. The mean daily tacrolimus dose in the Native Americans was 0.03 ± 0.02 compared with the Caucasians 0.5 ± 0.3 (mg/kg/d; P = .002), with no significant differences in trough levels, (6.7 ± 3.1 vs 7.4 ± 2.1 ng/dL; P = .4). Many Native Americans, but not Caucasians, demonstrated the 3/*3 - C3435T CC and the *3/*3 -G2677T GG genotype combination previously associated with low tacrolimus dosing. Native Americans required significantly lower tacrolimus doses than Caucasians to achieve similar tacrolimus trough levels, in part due to lower tacrolimus clearance from decreased drug metabolism and excretion.

Conversion from twice-daily tacrolimus to once-daily extended release tacrolimus (LCPT): the phase III randomized MELT trial

Phase III noninferiority trial examining efficacy and safety of converting stable renal transplant recipients from twice-daily tacrolimus to a novel extended-release once-daily tacrolimus formulation (LCPT) with a controlled agglomeration technology. Controls maintained tacrolimus twice daily. The primary efficacy endpoint was proportion of patients with efficacy failures (death, graft failure, locally read biopsy-proven acute rejection [BPAR], or loss to follow-up) within 12 months. Starting LCPT dose was 30% lower (15% for blacks) than preconversion tacrolimus dose; target trough levels were 4-15 ng/mL. A total of 326 patients were randomized; the mITT population (n = 162 each group) was similar demographically in the two groups. Mean daily dose of LCPT was significantly (p < 0.0001) lower than preconversion tacrolimus dose at each visit; mean trough levels between groups were similar. There were four efficacy failures in each group; safety outcomes were similar between groups. Frequency of premature study drug discontinuation was LCPT: 12% versus tacrolimus twice daily: 5% (p = 0.028). LCPT demonstrated noninferiority to tacrolimus twice daily in efficacy failure rates. LCPT may offer a safe and effective alternative for converting patients to a once-daily formulation. Compared to currently available tacrolimus formulation, LCPT requires lower doses to achieve target trough levels.

Effect of corticosteroid withdrawal on tacrolimus and mycophenolate mofetil exposure in a randomized multicenter study

As corticosteroid-sparing protocols are increasingly utilized in kidney transplant recipients, it is crucial to understand potential drug interactions between tacrolimus (TAC) and the effect of corticosteroid withdrawal as well as to characterize dose adjustments of mycophenolate mofetil (MMF) in this setting. This prospective, multicenter, randomized, double-blind study included 397 patients who were randomized on posttransplant day 8 to receive either placebo (CSWD) or corticosteroid continuance (CCS). TAC trough levels at week two posttransplant were significantly greater in the CSWD group whereas TAC doses were comparable to the CCS group. This interaction was not observed in the African American subgroup. Higher serum creatinine and potassium levels were also observed in the CSWD group. MMF dose was significantly reduced in the CSWD group by the investigators because of decreased WBC counts, mostly outside of study protocol criteria, despite similar incidence of neutropenia and reported cytomegalovirus infection. Understanding TAC and MMF exposure in the context of corticosteroid-sparing protocols should allow for improved dosing of immunosuppressants and better management of posttransplant patients.

Tacrolimus potently inhibits human osteoclastogenesis induced by IL-17 from human monocytes alone and suppresses human Th17 differentiation

Tacrolimus (FK506, Prograf®) is an orally available, T cell specific and anti-inflammatory agent that has been proposed as a therapeutic drug in rheumatoid arthritis (RA) patients. It has been known that T cells have a critical role in the pathogenesis of RA. Recent studies suggest that Th17 cells, which mainly produce IL-17, are involved in many autoimmune inflammatory disease including RA. The present study was undertaken to assess the effect of tacrolimus on IL-17-induced human osteoclastogenesis and human Th17 differentiation. Human CD14(+) monocytes were cultured in the presence of macrophage-colony stimulating factor (M-CSF) and IL-17. From day 4, tacrolimus was added to these cultures. Osteoclasts were immunohistologically stained for vitronectin receptor 10days later. IL-17 production from activated T cells stimulated with IL-23 was measured by enzyme-linked immunosorbent assay (ELISA). Th17 differentiation from naïve T cells was assayed by flow cytometry. Tacrolimus potently inhibited IL-17-induced osteoclastogenesis from human monocytes and osteoclast activation. Addition of tacrolimus also reduced production of IL-17 in human activated T cells stimulated with IL-23. Interestingly, the population of human IL-17(+)IFN-γ(-) CD4 T cells or IL-17(+)TNF-α(+) CD4 T cells were decreased by adding of tacrolimus. The present study demonstrates that the inhibitory effect of tacrolimus on IL-17-induced osteoclastogenesis from human monocytes. Tacrolimus also inhibited expression of IL-17 or TNF-α by reducing the proportion of Th17, suggesting that therapeutic effect on Th17-associated disease such as RA, inflammatory bowel disease, multiple sclerosis, psoriasis, or allograft rejection.