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

Background: This retrospective analysis of the US Scientific Registry of Transplant Recipients was undertaken to obtain real-world evidence concerning the efficacy and safety of tacrolimus-based immunosuppression in pediatric lung transplant recipients to support a supplemental New Drug Application., Methods: Overall, 725 pediatric recipients of a primary deceased-donor lung transplant between January 1, 1999, and December 31, 2017, were followed for up to 3 years post-transplant based on an immunosuppressive regimen at hospital discharge: immediate-release tacrolimus (TAC)+mycophenolate mofetil (MMF), TAC+azathioprine (AZA), cyclosporine (CsA)+MMF, or CsA+AZA. The primary outcome was the composite endpoint of graft failure or death (all-cause) at 1 year post-transplant, calculated by Kaplan-Meier analysis., Results: The use of TAC+MMF increased over time. During 2010 to 2017, 91.7% of pediatric lung transplant recipients were receiving TAC+MMF at the time of discharge. The proportion of recipients continuing their discharge regimen at 1 year post-transplant was 83.7% with TAC+MMF and 40.4% to 59.7% with the other regimens. Cumulative incidence of the composite endpoint of graft failure or death at 1 year post-transplant was 7.7% with TAC+MMF, 13.9% with TAC+AZA, 8.9% with CsA+MMF, and 9.1% with CsA+AZA. There was no significant difference in the risk of graft failure or death at 1 year post-transplant between groups from 1999 to 2005 (the only era when adequate numbers on each regimen allowed statistical comparison). No increase in hospitalization for infection or malignancy was seen with TAC+MMF., Conclusion: The real-world evidence from the US database of transplant recipients supported the Food and Drug Administration's approval of tacrolimus-based maintenance immunosuppression in pediatric lung transplant recipients., Competing Interests: Declaration of Competing Interest All authors report non-financial support from Astellas during the conduct of the study. Jay Erdman, David Nimke, Richard Croy, and Xuegong Wang are employees of Astellas Pharma, Inc. Josephine Wolfram is an employee of Astellas Pharma Europe BV. Tim Weaver and David Schladt are employees of Chronic Disease Research Group, an organization that generated data on behalf of Astellas. William E. Fitzsimmons is a former employee of Astellas Pharma, Inc. and is currently a pharma consultant working on behalf of Astellas, a co-founder of Azoth Immune Medicines, Inc, an advisory board member of CTI Clinical Trial and Consulting Services, a senior advisor to the Transplant Therapeutics Consortium, C-Path, and founder of Tutela Pharmaceuticals, Inc., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Competing Interests: The authors declare no conflicts of interest.

Background: The Scientific Registry of Transplant Recipients was retrospectively analyzed to provide real-world evidence of the efficacy and safety of tacrolimus-based immunosuppressive regimens in adult lung transplant recipients in the United States., Methods: Adult recipients (N = 25 355; ≥18 y) of a primary deceased-donor lung transplant between January 1, 1999, and December 31, 2017, were followed for 3 y posttransplant based on immunosuppressive regimen at discharge: immediate-release tacrolimus (TAC) + mycophenolate mofetil (MMF), TAC + azathioprine (AZA), cyclosporine (CsA) + MMF, or CsA + AZA. The primary outcome was the composite endpoint of graft failure or death (all-cause) at 1 y posttransplant (calculated via a modified Kaplan-Meier method)., Results: Discharge immunosuppressive regimens in lung transplant recipients changed over time, with a substantial increase in the use of TAC + MMF. TAC + MMF was the most common immunosuppressive regimen (received by 61.0% of individuals at discharge). The cumulative incidence of graft failure or death at 1 y posttransplant in adult lung transplant patients receiving TAC + MMF was 8.6% (95% confidence interval 8.1-9.1). Risk of graft failure or death was significantly higher in adults receiving CsA + MMF or CsA + AZA compared with TAC + MMF, with no significant difference seen between TAC + MMF and TAC + AZA. TAC + MMF had the highest continued use at 1 y posttransplant (72.0% versus 35.4%-51.5% for the other regimens). There was no increase in the rate of infection or malignancy in the TAC + MMF group., Conclusions: Real-world evidence from the most comprehensive database of transplant recipients in the United States supports the use of TAC in combination with MMF or AZA as maintenance immunosuppression in adult lung transplant recipients., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Background: The Scientific Registry of Transplant Recipients provides transplant program-specific information, but it is unclear what patients and stakeholders need to know. Acceptance criteria for the candidate waitlist and donor organs vary by program and region, but there is no means to search for programs by the clinical profiles of recipients and donors., Methods: We examined variability in program-specific characteristics that could influence access to transplantation. We also conducted three interviews and three focus groups with heart transplant candidates and recipients. Participants evaluated prototypes of a patient-specific search tool and its capacity to identify programs tailored to specific patient needs. Patient experiences and feedback influenced the development of tools., Results: The distribution of recipient and donor characteristics influenced access to transplantation, as age and body mass index varied across programs (all with p < .01). Several themes emerged related to decision-making and the perceived usability of the patient-specific search. Perceptions of the prototypes varied, but were positive overall and support making the patient-specific search publicly available. Participants revealed barriers to evaluating transplant programs and suggest that patient-specific search results may optimize the process., Conclusions: The patient-specific tool (http://transplantcentersearch.org/) is valued by heart transplant patients and is important to maximizing access to transplant., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Antibody-mediated rejection (AMR) is one of the leading causes of graft loss in kidney transplant recipients but little is known about the associated cost and healthcare burden of AMR., Methods: We developed an algorithm to detect AMR using the 2006-2011 Centers for Medicare & Medicaid Services (CMS) using ICD-10 and billing codes as there is no specific ICD-10 or procedure code for AMR. We then compared healthcare utilization, cost, and risk of graft failure or death in AMR. patients versus matched controls., Results: The algorithm had a 39.4% true-positive rate (69/175) and a 4.1% false-positive rate (110/2,655). We identified 5,679/101,554 (5.6%) with AMR, who had a nearly 3-fold higher risk of graft failure (hazard ratio [HR], 2.75, 95% confidence interval [CI], 2.50 to 3.03; p  < .0001) and death (HR, 2.59; 95% CI, 2.35 to 2.86; p  < .0001) at 2 years, nearly 5 times the hospitalizations in the 60 d before AMR diagnosis, and increased nephrology and emergency department visits. Mean AMR attributable healthcare costs were 4 times higher than matched controls, at $13,066 more per patient in the 60 d before AMR diagnosis and $35,740 per patient per year higher in the 2 years after AMR diagnosis., Conclusions: US kidney transplant recipients with AMR have substantially greater healthcare utilization and higher costs and risk of graft loss and mortality.

Background: Patients face obstacles in finding a transplant program that meets their healthcare needs. Acceptance criteria and waiting times vary by region and program. The Scientific Registry of Transplant Recipients provides program-specific information, but it is unclear what patients and referring physicians need to know., Methods: We examined variability in program-specific characteristics that could influence access to transplantation. We also conducted 20 interviews and 16 focus groups with transplant candidates, recipients, and their family members. Participants were shown prototypes of a patient-specific search tool and evaluated its capacity to identify programs tailored to the needs of individual patients., Results: The distribution of recipient and donor characteristics that may impact access to transplantation, such as recipients on Medicaid, varied across programs (all with P < 0.01). Several themes emerged related to impressions of access to transplantation and the usability of patient-specific search functions. Perceptions of the prototypes and results varied, but were positive overall and support providing an individualized search of program level data. Participants revealed significant barriers to identifying and evaluating transplant programs and suggest that patient-specific search results reduce the anxiety associated with selecting a program., Conclusions: Providing patient-specific tools is valued by patients and important to maximizing access to transplant., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 The Author(s). Transplantation Direct. Published by Wolters Kluwer Health, Inc.)

Variations in candidate and donor acceptance criteria may influence access and mortality for liver transplantation. We sought to understand how recipient and donor characteristics vary across centers and how patients interpret this information, and we used these data to develop a tool to provide tailored information to candidates seeking a center (www.transplantcentersearch.org). We analyzed liver recipient data from the Scientific Registry of Transplant Recipients to determine how recipient and donor characteristics (eg, age, Medicaid use, and human immunodeficiency virus status) varied across programs. Data included recipients and donors at each US program between January 1, 2015, and December 31, 2017. The variation in characteristics was plotted with centers stratified by total transplant volume and by volume of each characteristic. A subset of characteristics was plotted to show variation over 3 years. We created mockups of potential reports displaying recipient characteristics alongside pretransplant and posttransplant outcomes and solicited feedback at patient and family interviews and focus groups, which included 39 individuals: 10 pilot interviews with candidates seeking liver transplant at the University of Minnesota-Fairview (UMNF) and 5 focus groups with 13 UMNF candidates, 6 UMNF family members, and 10 national recipients. Transcripts were analyzed using a thematic analysis. Several themes emerged: (1) Candidates experience gaps in existing education about center options; (2) patients requested information about how selection criteria might impact access to transplant; and (3) information tailored to a candidate's medical characteristics can inform decisions. Characteristics shown on mockups varied across centers (P < 0.01). Variation was widespread for small and large centers. In conclusion, variation exists in recipient and donor characteristics across centers. Liver transplant patients provide positive feedback upon viewing patient-specific search tools., (Copyright © 2019 by the American Association for the Study of Liver Diseases.)

Background: Two apolipoprotein L1 gene (APOL1) renal-risk variants in donors and African American (AA) recipient race are associated with worse allograft survival in deceased-donor kidney transplantation (DDKT) from AA donors. To detect other factors impacting allograft survival from deceased AA kidney donors, APOL1 renal-risk variants were genotyped in additional AA kidney donors., Methods: The APOL1 genotypes were linked to outcomes in 478 newly analyzed DDKTs in the Scientific Registry of Transplant Recipients. Multivariate analyses accounting for recipient age, sex, race, panel-reactive antibody level, HLA match, cold ischemia time, donor age, and expanded criteria donation were performed. These 478 transplantations and 675 DDKTs from a prior report were jointly analyzed., Results: Fully adjusted analyses limited to the new 478 DDKTs replicated shorter renal allograft survival in recipients of APOL1 2-renal-risk-variant kidneys (hazard ratio [HR], 2.00; P = 0.03). Combined analysis of 1153 DDKTs from AA donors revealed donor APOL1 high-risk genotype (HR, 2.05; P = 3 × 10), older donor age (HR, 1.18; P = 0.05), and younger recipient age (HR, 0.70; P = 0.001) adversely impacted allograft survival. Although prolonged allograft survival was seen in many recipients of APOL1 2-renal-risk-variant kidneys, follow-up serum creatinine concentrations were higher than that in recipients of 0/1 APOL1 renal-risk-variant kidneys. A competing risk analysis revealed that APOL1 impacted renal allograft survival, but not recipient survival. Interactions between donor age and APOL1 genotype on renal allograft survival were nonsignificant., Conclusions: Shorter renal allograft survival is reproducibly observed after DDKT from APOL1 2-renal-risk-variant donors. Younger recipient age and older donor age have independent adverse effects on renal allograft survival.

Background: In addition to HLA genetic incompatibility, non-HLA difference between donor and recipients of transplantation leading to allograft rejection are now becoming evident. We aimed to create a unique genome-wide platform to facilitate genomic research studies in transplant-related studies. We designed a genome-wide genotyping tool based on the most recent human genomic reference datasets, and included customization for known and potentially relevant metabolic and pharmacological loci relevant to transplantation., Methods: We describe here the design and implementation of a customized genome-wide genotyping array, the 'TxArray', comprising approximately 782,000 markers with tailored content for deeper capture of variants across HLA, KIR, pharmacogenomic, and metabolic loci important in transplantation. To test concordance and genotyping quality, we genotyped 85 HapMap samples on the array, including eight trios., Results: We show low Mendelian error rates and high concordance rates for HapMap samples (average parent-parent-child heritability of 0.997, and concordance of 0.996). We performed genotype imputation across autosomal regions, masking directly genotyped SNPs to assess imputation accuracy and report an accuracy of >0.962 for directly genotyped SNPs. We demonstrate much higher capture of the natural killer cell immunoglobulin-like receptor (KIR) region versus comparable platforms. Overall, we show that the genotyping quality and coverage of the TxArray is very high when compared to reference samples and to other genome-wide genotyping platforms., Conclusions: We have designed a comprehensive genome-wide genotyping tool which enables accurate association testing and imputation of ungenotyped SNPs, facilitating powerful and cost-effective large-scale genotyping of transplant-related studies.

Variants in donor multidrug resistance protein 1 (ABCB1) and caveolin 1 (CAV1) genes are associated with renal allograft failure after transplantation in Europeans. Here we assessed transplantation outcomes of kidneys from 368 African American (AA) and 314 European American (EA) deceased donors based on 38 single-nucleotide polymorphisms (SNPs) spanning ABCB1 and 16 SNPs spanning CAV1, including previously associated index and haplotype-tagging SNPs. Tests for association with time to allograft failure were performed for the 1233 resultant kidney transplantations, adjusting for recipient age, sex, ethnicity, cold ischemia time, panel reactive antibody, human leukocyte antigen match, expanded-criteria donation, and APOL1-nephropathy variants in AA donors. Interaction analyses between APOL1 with ABCB1 and CAV1 were performed. In a meta-analysis of all transplantations, ABCB1 index SNP rs1045642 was associated with time to allograft failure and other ABCB1 SNPs were nominally associated, but not CAV1 SNPs. ABCB1 SNP rs1045642 showed consistent effects with the 558 transplantations from EA donors, but not with the 675 transplantations from AA donors. ABCB1 SNP rs956825 and CAV1 SNP rs6466583 interacted with APOL1 in transplants from AA donors. Thus, the T allele at ABCB1 rs1045642 is associated with shorter renal allograft survival for kidneys from American donors. Interactions between ABCB1 and CAV1 with APOL1 may influence allograft failure for transplanted kidneys from AA donors.

Most calcineurin inhibitor (CNI)-based protocols reduce blood trough goals approximately 2-3 months post-transplant in clinically stable kidney transplant recipients. The CNI target trough level to prevent rejection, after reduction, is unknown. Using a multivariate Cox proportional hazards model, we determined the association of time-varying tacrolimus (TAC) trough levels with acute rejection (AR) occurring in the first 6 months post-transplant, but specifically we assessed this association after 3 months. A total of 1930 patients received TAC-based immunosuppression prior to AR in a prospective study. Of the 151 (7.8%) who developed AR, 47 developed AR after 3 months post-transplant. In an adjusted time-varying multivariate model, each 1 ng/ml decrease in TAC trough levels was associated with a 7.2% increased risk of AR [hazards ratio (HR) = 1.07, 95% confidence interval (CI) (1.01, 1.14) P = 0.03] in the first 6 months. There was an additional 23% increased risk of AR with each 1 ng/ml decrease in the TAC trough levels in months 3-6 [HR = 1.23, 95% CI (1.06, 1.43) P = 0.008]. In conclusion, lower TAC trough levels were significantly associated with increased risk of AR in the first 6 months post-transplant with additional risk of AR between months 3 and 6 post-transplant. The timing and practice of TAC dose reduction should be personalized based on the individual's risk factors., (© 2013 Steunstichting ESOT. Published by John Wiley & Sons Ltd.)

Background: Chronic allograft dysfunction (CGD) is a common outcome in kidney transplants, but its pathogenesis is unclear. We investigated the CGD phenotype and single-nucleotide polymorphisms (SNPs) associated with CGD., Method: This prospective study enrolled 2336 transplants from seven transplant centers in North America. CGD was defined as a >25% rise in serum creatinine relative to a three-month post-transplant baseline, requiring a kidney biopsy. We genotyped 2724 SNPs in the initial 979 transplants, which form the test cohort., Results: CGD occurred 11.2 times per 100 person-years at a median of 509 ± 387 days from the three-month baseline. CGD was independently associated with death-censored, allograft failure, in an adjusted analysis [HR=20.6 (11.8-35.8, p < 0.001)]. Among 366 transplant recipients with CGD, 91% had inflammation on biopsy scores. 94 (26%) had inflammatory changes consistent with a diagnosis of concomitant acute rejection. SNPs in FM06 and FM03, potential drug metabolism genes, were associated with CGD, after accounting for multiple testing., Conclusion: CGD phenotype with concomitant inflammation is associated with increased risk of allograft failure. SNPs associated with CGD in novel drug metabolism and transport genes, will be validated in subsequent transplants., (© 2013 John Wiley & Sons A/S.)

Background: Calcineurin inhibitor (CNI)-related acute nephrotoxicity is a common complication of transplantation. Clinical factors and elevated CNI levels are associated with nephrotoxicity; however, they do not fully explain the risk. Genetic factors may also predispose individuals to nephrotoxicity., Methods: We enrolled 945 kidney recipients into a multicenter, prospective study. DNA was genotyped for 2724 single-nucleotide polymorphisms (SNPs) using a customized chip. Cox models, unadjusted and adjusted for clinical factors, examined the association between SNPs and time to early CNI-related acute nephrotoxicity in the first 6 months posttransplant., Results: Cyclosporine was associated with a 1.49 hazard (95% confidence interval, 1.04-2.14) of acute nephrotoxicity relative to tacrolimus. Acute nephrotoxicity occurred in 22.6% of cyclosporine and 19.8% of tacrolimus recipients. The median (interquartile range) daily dose and trough concentration at time of nephrotoxicity were 400 mg (400-500 mg) and 228 ng/mL (190-272 ng/mL) in the cyclosporine group, and 6 mg (4-8 mg) and 12.6 ng/mL (10.2-15.9 ng/mL) in the tacrolimus group, respectively. In single-SNP adjusted analysis, nine SNPs in the XPC, CYP2C9, PAX4, MTRR, and GAN genes were associated with cyclosporine nephrotoxicity. In a multi-SNP analysis, SNPs from the same genes remained significant after adjusting for the clinical factors, showing that the SNPs are jointly and independently predictive of cyclosporine nephrotoxicity. No SNPs were associated with tacrolimus nephrotoxicity., Conclusion: We identified SNPs that were potentially associated with early, acute cyclosporine-related nephrotoxicity. Identifying risk SNPs before transplantation provides an opportunity for personalization of immunosuppression by identifying those who may benefit from CNI-avoidance or minimization, or assist in selecting CNI type. These SNPs require independent validation.

Background: Mycophenolate-related anemia and leukopenia are well-known toxicities after transplantation. Toxicity leads to dose reduction, addition of colony-stimulating factors or erythropoietin, or discontinuation of immunosuppressive therapy. The causes of and risk factors associated with toxicity are unclear., Methods: We studied the association between mycophenolate-related anemia and leukopenia and 2724 single nucleotide polymorphisms (SNP) in 978 patients undergoing living or deceased donor kidney transplant. Patients were followed up to time of first anemia (hemoglobin<10 gm/dL or hematocrit<30%) or first leukopenia (white blood cell [WBC] count <3000 cells/mm), which required clinical intervention in the first 6 months after transplant., Results: Anemia occurred in 87 (9.5%) subjects and leukopenia in 224 (22.9%). In single SNP analyses, none of the SNPs were associated with time to leukopenia at a false discovery rate (FDR) of 20%. However, SNPs from the IL12A, HUS, CYP2C8 genes were associated with time to anemia, allowing for an FDR of 20%. To assess the independence of these SNPs as predictors of anemia, we conducted a multi-SNP analysis including one SNP from each of the three genes. All three SNPs were associated with time to anemia, after adjusting for recipient age, weight, posttransplant dialysis and antiviral drug use, and stratifying by clinical center., Conclusion: Although these SNPs require validation in an independent population, our results suggest that genetics may play a role in risk of mycophenolate-related hematologic toxicity. This may ultimately provide for better management of maintenance immunosuppression and gives insights into potential mechanism(s) by which toxicity occurs.

Background: The CYP4503A5*1 genotype is associated with lower tacrolimus concentrations. Although its effect is important, it incompletely explains the variability in tacrolimus concentrations and has a relatively low minor allele frequency in whites relative to African Americans (AA)., Methods: We studied clinical and recipient genetic correlates of dose-normalized tacrolimus troughs (n=12,277) in the first 6 months posttransplant using a customized single-nucleotide polymorphism chip with 2722 variants in a large, ethnically diverse (144 AA and 551 non-AA) adult kidney transplant population through a seven-center consortium., Results: During the 6-month study, AAs had consistently lower median (interquartile range) troughs than non-AAs, 6.2 (4.4-8.4) ng/mL vs. 8.3 (6.4-10.4) ng/mL (P<0.0001), despite 60% higher daily doses, 8 (5-10) mg vs. 5 (4-7) mg (P<0.0001). The median tacrolimus trough concentration in week 1 posttransplant was particularly low in AAs (2.1 [1.2-3.5] ng/mL) compared with non-AAs (5.0 [3.1-8.2] ng/mL) (P<0.0001), despite similar initial doses. In single-variant analysis, CYP3A5*3 (rs776746) was the top variant (P=2.4×10) associated with troughs. After adjustment for CYP3A5*3, clinical factors and race, 35 additional variants were identified (P<0.01, not significant at false discovery rate 20%). In the final multivariant, regression models beginning with these variants and clinical factors, seven variants were identified in the non-AA and seven variants in the AA group towards the first trough concentrations. Rs776746 (CYP3A5), rs2239393 (COMT) and diabetes were the only factors common in both populations., Conclusion: We identified variants beyond CYP3A5*3, which may further explain pharmacokinetic variability of tacrolimus and demonstrated that important variants differ by race.

Background: Acute rejection (AR) is associated with worse renal allograft outcomes. Therefore, this study investigated single-nucleotide polymorphisms (SNPs) to identify genetic variants associated with AR, accounting for center variation, in a multicenter, prospective, observation study., Methods: We enrolled patients from six transplant centers, five in the United States and one in Canada. A total of 2724 SNPs were genotyped. We accounted for center variation in AR rates by stratifying by transplant center and using novel knowledge discovery methods., Results: There was significant center variation in AR rates across the six transplant sites (P<0.0001). Accounting for this difference and clinical factors independently associated with AR, we identified 15 novel SNPs associated with AR with stratification by transplant center (P<0.05). We also identified 15 novel SNPs associated with severity of tubulitis scores, after adjusting for transplant center and other clinical factors independently associated with severity of tubulitis (P<0.05). There was some overlap with one SNP associated with AR and also associated with severity of tubulitis, among the top 15 SNPs., Conclusion: Center-to-center variation is a major challenge to genomic studies focused on AR. The SNPs associated with AR and severity of tubulitis in this study will need to be validated in independent cohort of kidney transplant recipients.