Faculty Bibliography

BACKGROUND/UNASSIGNED:Imlifidase is an IgG-cleaving endopeptidase conditionally approved in Europe for desensitization of highly sensitized patients before kidney transplantation. We present 5-y outcomes and donor-specific antibody (DSA) levels for clinical trial participants from a single site who received imlifidase for desensitization before incompatible transplantation (NCT02790437). METHODS/UNASSIGNED:Imlifidase was administered up to 24 h before living or deceased donor kidney transplantation. DSAs were monitored before transplantation, at days 7 and 28, and at 5 y posttransplant. RESULTS/UNASSIGNED:At 5 y, 7 of 8 participants were alive. One of these 7 had suboptimal graft function secondary to donor-derived disease but remained dialysis independent. Three participants had antibody-mediated rejection (AMR), which occurred in the first 30 d in all cases and was successfully treated. No new episodes of suspected or biopsy-proven AMR occurred after 30 d posttransplant. Seven participants had DSA rebound. DSAs commonly persisted 5 y posttransplant, although they were generally lower strength compared with pre-imlifidase. Dilution studies of sensitized serum enabled the identification of lower AMR risk phenotypes for persisting DSAs. Severe and/or opportunistic infections were not observed at greater than expected frequency. CONCLUSIONS/UNASSIGNED:Five-year outcomes of imlifidase-enabled incompatible transplants are overall favorable. DSA rebound is common, but antibody strength lessens in the long term, and longitudinally persisting DSAs did not lead to premature graft failure.

BACKGROUND/UNASSIGNED:Imlifidase is an IgG-cleaving endopeptidase conditionally approved in Europe for desensitization of highly sensitized patients before kidney transplantation. We present 5-y outcomes and donor-specific antibody (DSA) levels for clinical trial participants from a single site who received imlifidase for desensitization before incompatible transplantation (NCT02790437). METHODS/UNASSIGNED:Imlifidase was administered up to 24 h before living or deceased donor kidney transplantation. DSAs were monitored before transplantation, at days 7 and 28, and at 5 y posttransplant. RESULTS/UNASSIGNED:At 5 y, 7 of 8 participants were alive. One of these 7 had suboptimal graft function secondary to donor-derived disease but remained dialysis independent. Three participants had antibody-mediated rejection (AMR), which occurred in the first 30 d in all cases and was successfully treated. No new episodes of suspected or biopsy-proven AMR occurred after 30 d posttransplant. Seven participants had DSA rebound. DSAs commonly persisted 5 y posttransplant, although they were generally lower strength compared with pre-imlifidase. Dilution studies of sensitized serum enabled the identification of lower AMR risk phenotypes for persisting DSAs. Severe and/or opportunistic infections were not observed at greater than expected frequency. CONCLUSIONS/UNASSIGNED:Five-year outcomes of imlifidase-enabled incompatible transplants are overall favorable. DSA rebound is common, but antibody strength lessens in the long term, and longitudinally persisting DSAs did not lead to premature graft failure.

INTRODUCTION/BACKGROUND:Some living organ donors will decide to donate again at a later date. Evidence has indicated that this practice may have increased in recent years. We evaluated the incidence and outcomes of this practice to inform counseling of potential repeat donors. METHODS:Using SRTR data from 1994 to 2023, we identified 220 repeat living donors and their 415 recipients. We constructed donor comparison groups using weighting by the odds. We described clinical and lab results at 6 months, 1 year, and 2 years post-donation separately for kidney-second donors and liver-second donors. We compared all-cause graft failure for their recipients with those of comparison donors. RESULTS:The annual count of repeat living donors increased from 5 in 2018 to 25 in 2019 (p < 0.001). Of 220 donors, 159 were liver-second donors (72.3%) and 55 were kidney-second donors (25.0). The percentage of nondirected donations increased from 30.5% at first donation to 53.2% at second donation (p < 0.001). Liver-second donors had one death approximately 2.5 years post-donation. Seventeen were re-admitted and 20 experienced complications requiring an interventional procedure or re-operation. Among kidney-second donors, no deaths, re-admissions, or post-donation complications were reported. Post-donation outcomes in both groups were comparable when evaluated against organ-specific comparison donors. Recipients of repeat living donors experienced graft survival similar to recipients of comparison donors. CONCLUSIONS:Repeat living donation may be a safe practice for carefully selected living donors in the short term; however, long term safety is unknown. Outcomes for recipients are similar to recipients of comparison donors.

Human leukocyte antigen-level matching in US kidney allocation has been deemphasized due to its role in elevating racial disparities. Molecular matching based on eplets might improve risk stratification compared to antigen matching, but the magnitude of racial disparities in molecular matching is not known. To assign eplets unambiguously, we utilized a cohort of 5193 individuals with high-resolution allele-level human leukocyte antigen genotypes from the National Kidney Registry. Using repeated random sampling to simulate donor-recipient genotype pairings based on the ethnic composition of the historical US deceased-donor pool, we profiled the percentage of well-matched donors available for candidates by ethnicity. The prevalence of well-matched donors with 0-DR/DQ eplet mismatch was 3-fold less racially disparate for Black and Asian candidates and 2-fold less for Latino candidates compared to 0-ABDR antigen mismatches. Compared to 0-DR antigen mismatch, 0-DR eplet mismatch was 1.33-fold more racially disparate for Asian and 1.28-fold more for Latino, with similar disparity for Black candidates, whereas 0-DQ eplet mismatch reduced disparities, showing 1.26-fold less disparity for Black, 1.14-fold less for Latino, but 1.26-fold higher for Asian candidates. The prevalence of well-matched donors for candidates of different ethnicities varied according to which molecules were chosen to define a low-risk match.

The degree of immunological compatibility between donors and recipients greatly impacts allograft survival. In the United States kidney allocation system, HLA antigen-level matching has been shown to cause ethnic disparities and thus, has been de-emphasised. However, priority points are still awarded for antigen-level zero-ABDR matching, zero-DR matching and one-DR matching. Recently, the degree of HLA molecular (eplet) mismatch has emerged as a more accurate measure of immunological risk, and eplet mismatch load has gained attention as a possible biomarker to improve HLA compatibility. However, little is known about the frequency of eplets in population groups, which is a necessary step to ensure that candidates from any ethnical background can have similar chances at a well-matched organ. Eplet frequencies were estimated using HLA alleles in the Common, Intermediate and Well-Documented (CIWD) 3.0.0 catalogue for six population groups: African-American (AFA), Asian-Pacific Islander (API), European/European descent (EURO), Middle East/North Coast of Africa (MENA), Hispanic/Latino (HIS) and Native-American (NAM). We determined that 98.6% (484 out of 491) of HLA eplets are expressed by the common HLA alleles in all population groups. Of the seven eplets that were expressed by less common HLA alleles, six were Class I eplets and one was expressed by HLA-DQB1 alleles and most were expressed by HLA alleles that were more commonly observed in European/European descent populations. Our observations indicate that HLA eplets will not cause any significant disparity if applied to HLA molecular compatibility, regardless of the ethnic origin of both recipients and donors.

BACKGROUND AND HYPOTHESIS/OBJECTIVE:Hepatitis C virus (HCV) positive-to-negative kidney transplants (KT) require direct acting antiviral therapy, but the optimal timing and duration remain unclear. We hypothesized that 14-day prophylactic course of glecaprevir/pibrentasvir 300/120 mg (GLE/PIB) would be safe and effective at treating donor-derived HCV viremia. METHODS:This was a prospective, single-center, single-arm, open-label pilot study. 20 adult HCV negative recipients of HCV nucleic acid amplification test positive deceased-donor kidneys (HCV positive-to-negative) received a 14-day course of GLE/PIB, with the first dose pre-transplant. HCV RNA viral loads (VL) were monitored on post-operative days (POD) 1, 3, 7, and 13. If VL was undetectable on POD 13, GLE/PIB was stopped, and if detectable, GLE/PIB was continued to complete an 8-week course. Surveillance monitoring continued after treatment to ensure sustained viral response (SVR). The primary outcome was efficacy of 14-day prophylactic GLE/PIB. Secondary outcomes included patient and allograft survival, the incidence, timing, and clearance of HCV viremia, and safety events. RESULTS:7/20 subjects (35%) never developed detectable HCV viremia. Only one subject had a detectable, but nonquantifiable, VL on POD 13 and completed an 8-week course. All subjects achieved SVR 12 weeks post-treatment with no relapses through 1-year follow-up. Mean time to undetectable HCV RNA VL was 10.5 (±4.7) days and mean peak VL was 371 (±715) copies/mL. 6-month and 1-year patient and allograft survival were 100% and 95%. CONCLUSION/CONCLUSIONS:A 14-day course of prophylactic GLE/PIB is safe and effective for HCV positive-to-negative KT and may prevent HCV transmission or significantly reduce the VL for those with detectable transmission allowing for rapid clearance within 2 weeks.

Developing real-world evidence from electronic health records (EHR) is vital to advance kidney transplantation (KT). We assessed the feasibility of studying KT using the Epic Cosmos aggregated EHR dataset, which includes 274 million unique individuals cared for in 238 U.S. health systems, by comparing it with the Scientific Registry of Transplant Recipients (SRTR). We identified 69,418 KT recipients transplanted between January 2014 and December 2022 in Cosmos (39.4% of all US KT transplants during this period). Demographics and clinical characteristics of recipients captured in Cosmos were consistent with the overall SRTR cohort. Survival estimates were generally comparable, although there were some differences in long-term survival. At 7 years post-transplant, patient survival was 80.4% in Cosmos and 77.8% in SRTR. Multivariable Cox regression showed consistent associations between clinical factors and mortality in both cohorts, with minor discrepancies in the associations between death and both age and race. In summary, Cosmos provides a reliable platform for KT research, allowing EHR-level clinical granularity not available with either the transplant registry or healthcare claims. Consequently, Cosmos will enable novel analyses to improve our understanding of KT management on a national scale.