Pegloticase efficacy and safety in kidney transplant recipients; results of the phase IV, open-label PROTECT clinical trial.

INTRODUCTION: Kidney transplant (KT) recipients have a high prevalence and severity of gout. Pegloticase (pegylated recombinant uricase) rapidly metabolizes serum uric acid (sUA), and its efficacy is not impacted by kidney function. METHODS: This open-label, Phase 4 trial (PROTECT NCT04087720) examined safety and efficacy of pegloticase in 20 participants with KT > 1 year prior to enrollment and with uncontrolled gout (sUA ≥7 mg/dL, intolerance/inefficacy to urate lowering therapy, and ≥1 of the following: tophi, chronic gouty arthritis, ≥2 flares in past year) and functioning KT (estimated glomerular filtration rate [eGFR] ≥15 mL/min/1.73 m2 ) on stable immunosuppression therapy. RESULTS: The primary endpoint was sUA response during month 6 (sUA < 6 mg/dL for ≥80% of time). The study enrolled 20 participants (mean ± SD); age: 53.9 ± 10.9 years, time since KT: 14.7 ± 6.9 years, sUA: 9.4 ± 1.5 mg/dL, gout duration: 8.4 ± 11.6 years; all on ≥2 stable doses of immunosuppression agents. Pegloticase (8 mg intravenous every 2 weeks) in KT recipients with uncontrolled gout showed a high response rate of 89% (16/18 responders). Two participants discontinued treatment solely due to COVID-19 concerns prior to month 6 were not included in the primary analysis. Pegloticase exposures were higher than those historically observed with pegloticase monotherapy, and no anaphylaxis or infusion reaction events occurred during the study. CONCLUSIONS: This improved response rate to pegloticase in the KT population reflects observations from other trials and reports on immunomodulation with pegloticase. As the KT population has a high prevalence of gout and limitations with oral urate lowering medication options, these findings suggest a potential option for uncontrolled gout therapy in KT participants.

Successful Induction of Specific Immunological Tolerance by Combined Kidney and Hematopoietic Stem Cell Transplantation in HLA-Identical Siblings.

Induction of immunological tolerance has been the holy grail of transplantation immunology for decades. The only successful approach to achieve it in patients has been a combined kidney and hematopoietic stem cell transplantation from an HLA-matched or -mismatched living donor. Here, we report the first three patients in Europe included in a clinical trial aiming at the induction of tolerance by mixed lymphohematopoietic chimerism after kidney transplantation. Two female and one male patient were transplanted with a kidney and peripherally mobilized hematopoietic stem cells from their HLA-identical sibling donor. The protocol followed previous studies at Stanford University: kidney transplantation was performed on day 0 including induction with anti-thymocyte globulin followed by conditioning with 10x 1.2 Gy total lymphoid irradiation and the transfusion of CD34+ cells together with a body weight-adjusted dose of donor T cells on day 11. Immunosuppression consisted of cyclosporine A and steroids for 10 days, cyclosporine A and mycophenolate mofetil for 1 month, and then cyclosporine A monotherapy with tapering over 9-20 months. The 3 patients have been off immunosuppression for 4 years, 19 months and 8 months, respectively. No rejection or graft-versus-host disease occurred. Hematological donor chimerism was stable in the first, but slowly declining in the other two patients. A molecular microscope analysis in patient 2 revealed the genetic profile of a normal kidney. No relevant infections were observed, and the quality of life in all three patients is excellent. During the SARS-CoV-2 pandemic, all three patients were vaccinated with the mRNA vaccine BNT162b2 (Comirnaty®), and they showed excellent humoral and in 2 out 3 patients also cellular SARS-CoV-2-specific immunity. Thus, combined kidney and hematopoietic stem cell transplantation is a feasible and successful approach to induce specific immunological tolerance in the setting of HLA-matched sibling living kidney donation while maintaining immune responsiveness to an mRNA vaccine (ClinicalTrials.gov: NCT00365846).

Development of immunosuppressive myeloid cells to induce tolerance in solid organ and hematopoietic cell transplant recipients.

Replacement of failed organs followed by safe withdrawal of immunosuppressive drugs has long been the goal of organ transplantation. We studied changes in the balance of T cells and myeloid cells in the blood of HLA-matched and -mismatched patients given living donor kidney transplants followed by total lymphoid irradiation, anti-thymocyte globulin conditioning, and donor hematopoietic cell transplant to induce mixed chimerism and immune tolerance. The clinical trials were based on a conditioning regimen used to establish mixed chimerism and tolerance in mice. In preclinical murine studies, there was a profound depletion of T cells and an increase in immunosuppressive polymorphonuclear (pmn) myeloid-derived suppressor cells (MDSCs) in the spleen and blood following transplant. Selective depletion of pmn MDSCs in mice abrogated mixed chimerism and tolerance. In our clinical trials, patients given an analogous tolerance conditioning regimen developed similar changes, including profound depletion of T cells and a marked increase in MDSCs in blood posttransplant. Posttransplant pmn MDSCs transiently increased expression of lectin-type oxidized LDL receptor-1, a marker of immunosuppression, and production of the T-cell inhibitor arginase-1. These posttransplant pmn MDSCs suppressed the activation, proliferation, and inflammatory cytokine secretion of autologous T-cell receptor microbead-stimulated pretransplant T cells when cocultured in vitro. In conclusion, we elucidated changes in receptors and function of immunosuppressive myeloid cells in patients enrolled in the tolerance protocol that were nearly identical to those of MDSCs required for tolerance in mice. These trials were registered at www.clinicaltrials.gov as #NCT00319657 and #NCT01165762.

Mixed chimerism and acceptance of kidney transplants after immunosuppressive drug withdrawal.

Preclinical studies have shown that persistent mixed chimerism is linked to acceptance of organ allografts without immunosuppressive (IS) drugs. Mixed chimerism refers to continued mixing of donor and recipient hematopoietic cells in recipient tissues after transplantation of donor cells. To determine whether persistent mixed chimerism and tolerance can be established in patients undergoing living donor kidney transplantation, we infused allograft recipients with donor T cells and hematopoietic progenitors after posttransplant lymphoid irradiation. In 24 of 29 fully human leukocyte antigen (HLA)-matched patients who had persistent mixed chimerism for at least 6 months, complete IS drug withdrawal was achieved without subsequent evidence of rejection for at least 2 years. In 10 of 22 HLA haplotype-matched patients with persistent mixed chimerism for at least 12 months, reduction of IS drugs to tacrolimus monotherapy was achieved. Withdrawal of tacrolimus during the second year resulted in loss of detectable chimerism and subsequent rejection episodes, unless tacrolimus therapy was reinstituted. Posttransplant immune reconstitution of naïve B cells and B cell precursors was more rapid than the reconstitution of naïve T cells and thymic T cell precursors. Robust chimerism was observed only among naïve T and B cells but not among memory T cells. No evidence of rejection was observed in all surveillance graft biopsies obtained from mixed chimeric patients withdrawn from IS drugs, and none developed graft-versus-host disease. In conclusion, persistent mixed chimerism established in fully HLA- or haplotype-matched patients allowed for complete or partial IS drug withdrawal without rejection.

Macrochimerism and clinical transplant tolerance.

Current theory holds that macrochimerism is essential to the development of transplant tolerance. Hematopoietic cell transplantation from the solid organ donor is necessary to achieve macrochimerism. Over the last 10-20 years, trials of tolerance induction with combined kidney and hematopoietic cell transplantation have moved from the preclinical to the clinical arena. The achievement of macrochimerism in the clinical setting is challenging, and potentially toxic due to the conditioning regimen necessary to hematopoietic cell transplantation and due to the risk of graft-versus-host disease. There are differences in chimerism goals and methods of the three major clinical stage tolerance induction strategies in both HLA-matched and HLA-mismatched living donor kidney transplantation, with consequent differences in efficacy and safety. The Stanford protocol has proven efficacious in the induction of tolerance in HLA-matched kidney transplantation, allowing cessation of immunosuppressive drug therapy in 80% of study participants, with the safety profile of conventional transplantation. In HLA-mismatched transplantation, multi-lineage macrochimerism of over a year's duration can now be consistently achieved with the Stanford protocol, with complete withdrawal of immunosuppressive drug therapy during the second post-transplant year as the next experimental step and test of tolerance.

Developing Consensus-Based Priority Outcome Domains for Trials in Kidney Transplantation: A Multinational Delphi Survey With Patients, Caregivers, and Health Professionals.

BACKGROUND: Inconsistencies in outcome reporting and frequent omission of patient-centered outcomes can diminish the value of trials in treatment decision making. We identified critically important outcome domains in kidney transplantation based on the shared priorities of patients/caregivers and health professionals. METHODS: In a 3-round Delphi survey, patients/caregivers and health professionals rated the importance of outcome domains for trials in kidney transplantation on a 9-point Likert scale and provided comments. During rounds 2 and 3, participants rerated the outcomes after reviewing their own score, the distribution of the respondents' scores, and comments. We calculated the median, mean, and proportion rating 7 to 9 (critically important), and analyzed comments thematically. RESULTS: One thousand eighteen participants (461 [45%] patients/caregivers and 557 [55%] health professionals) from 79 countries completed round 1, and 779 (77%) completed round 3. The top 8 outcomes that met the consensus criteria in round 3 (mean, ≥7.5; median, ≥8; proportion, >85%) in both groups were graft loss, graft function, chronic rejection, acute rejection, mortality, infection, cancer (excluding skin), and cardiovascular disease. Compared with health professionals, patients/caregivers gave higher priority to 6 outcomes (mean difference of 0.5 or more): skin cancer, surgical complications, cognition, blood pressure, depression, and ability to work. We identified 5 themes: capacity to control and inevitability, personal relevance, debilitating repercussions, gaining awareness of risks, and addressing knowledge gaps. CONCLUSIONS: Graft complications and severe comorbidities were critically important for both stakeholder groups. These stakeholder-prioritized outcomes will inform the core outcome set to improve the consistency and relevance of trials in kidney transplantation.

HCV infection is associated with lower survival in simultaneous liver kidney transplant recipients in the United States.

BACKGROUND: The frequency of simultaneous liver kidney transplantation (SLKT) has been increasing over the past decade. Hepatitis C virus (HCV) infection is the most common indication for liver transplantation in the United States. Given the rising prevalence of HCV-related SLKT, it is important to understand the impact of HCV in this patient population. METHODS: We conducted a retrospective cohort study using data from the United Network for Organ Sharing registry to assess adult patients undergoing SLKT in the United States from 2003 to 2012. Patient survival following SLKT was assessed using Kaplan-Meier methods and multivariate Cox proportional hazards models. RESULTS: Patients infected with non-HCV have significantly lower survival following SLKT compared to non-HCV patients at three (three-yr survival: 71.0% vs. 78.9%, p < 0.01) and five yr (five-yr survival: 61.4% vs. 72.5%, p < 0.01). The results of multivariate regression analyses demonstrated that patients infected with HCV had significantly lower survival following SLKT than patients with non-HCV disease (HR 1.41, 95% CI, 1.19-1.67, p < 0.001). In addition, lower post-SLKT survival was noted among patients with diabetes (HR 1.34, 95% CI, 1.13-1.58, p < 0.001) and hepatocellular carcinoma (HR 1.60, 95% CI, 1.17-2.18, p < 0.01). CONCLUSIONS: Hepatitis C infection is associated with lower patient survival following SLKT.

Tolerance and chimerism after renal and hematopoietic-cell transplantation.

We describe a recipient of combined kidney and hematopoietic-cell transplants from an HLA-matched donor. A post-transplantation conditioning regimen of total lymphoid irradiation and antithymocyte globulin allowed engraftment of the donor's hematopoietic cells. The patient had persistent mixed chimerism, and the function of the kidney allograft has been normal for more than 28 months since discontinuation of all immunosuppressive drugs. Adverse events requiring hospitalization were limited to a 2-day episode of fever with neutropenia. The patient has had neither rejection episodes nor clinical manifestations of graft-versus-host disease.

Validation of a screening protocol for identifying low-risk candidates with type 1 diabetes mellitus for kidney with or without pancreas transplantation.

BACKGROUND: Certain clinical risk factors are associated with significant coronary artery disease in kidney transplant candidates with diabetes mellitus. We sought to validate the use of a clinical algorithm in predicting post-transplantation mortality in patients with type 1 diabetes. We also examined the prevalence of significant coronary lesions in high-risk transplant candidates. METHODS: All patients with type 1 diabetes evaluated between 1991 and 2001 for kidney with/without pancreas transplantation were classified as high-risk based on the presence of any of the following risk factors: age >or=45 yr, smoking history >or=5 pack years, diabetes duration >or=25 yr or any ST-T segment abnormalities on electrocardiogram. Remaining patients were considered low risk. All high-risk candidates were advised to undergo coronary angiography. The primary outcome of interest was all-cause mortality post-transplantation. RESULTS: Eighty-four high-risk and 42 low-risk patients were identified. Significant coronary artery stenosis was detected in 31 high-risk candidates. Mean arterial pressure was a significant predictor of coronary stenosis (odds ratio 1.68; 95% confidence interval 1.14-2.46), adjusted for age, sex and duration of diabetes. In 75 candidates who underwent transplantation with median follow-up of 47 months, the use of clinical risk factors predicted all eight deaths. No deaths occurred in low-risk patients. A significant mortality difference was noted between the two risk groups (p = 0.03). CONCLUSIONS: This clinical algorithm can identify patients with type 1 diabetes at risk for mortality after kidney with/without pancreas transplant. Patients without clinical risk factors can safely undergo transplantation without further cardiac evaluation.

The role of pre-emptive re-transplant in graft and recipient outcome.

BACKGROUND: The effect of the pre-emptive re-transplant, and of inter-transplant waiting time generally, on graft and recipient survival is not well established. METHODS: Analysis of the United States Renal Data System (USRDS) data (1/1/90 through 12/31/00; n = 92,844) was performed. Cox regression was used to analyse time to event, with an additional analysis to stratify by transplant era. RESULTS: Having a prior transplant, as well as the total number of transplants, was related to an increased risk of graft failure [hazard ratio (HR) 1.24, P<0.001 for history of prior transplant; HR 1.35 per transplant, P<0.001], but not to recipient death. The time waiting for re-transplant slightly worsened the risk for recipient mortality in the entire patient population and in the recipients of single re-transplant (HR 1.003 and 1.004 per month respectively, P<0.001), and for graft failure only in recipients of single re-transplant (HR 1.001 per month, P<0.05). Pre-emptive re-transplant (dialysis-free re-transplant or transplant within 6 days of last graft failure) increased the risk of graft failure (HR 1.36, P<0.001) and did not have any statistically significant effect on recipient survival. The longer duration of prior graft survival but not the type of the graft (living vs deceased) had protective effect on the consecutive graft and recipient survival. CONCLUSIONS: With the potential caveats associated with retrospective data analysis, these results suggest that pre-emptive re-transplantation is associated with increased risk of graft failure, while longer time on dialysis in between transplants is associated with negative effect upon graft and recipient survival in most patient subgroups. The optimal time in between graft failure and re-transplant was not evaluated in this study. Further prospective studies might be needed to confirm the observed effects.

The role of pretransplantation renal replacement therapy modality in kidney allograft and recipient survival.

BACKGROUND: The effect of pretransplantation renal replacement therapy (RRT) modality on allograft and recipient survival outcome is not well understood. METHODS: We studied allograft and recipient survival by using US Renal Data System records from January 1, 1990, to December 31, 1999, with a follow-up period through December 31, 2000 (n = 92,844; 60% males; 70% white; 23% black). Pretransplantation and predominant RRT modality during the end-stage renal disease (ESRD) period and number and specific combinations of RRT modalities were evaluated. RESULTS: Compared with hemodialysis (HD), a Cox model showed that peritoneal dialysis (PD) immediately before transplantation predicts a 3% lower risk for graft failure (P < 0.05) and 6% lower risk for recipient death (P < 0.001). When predominant RRT modality was analyzed (modality used for > 50% of the ESRD time), PD (hazard ratio [HR], 0.97; P < 0.05) had a protective effect for graft survival compared with HD. Better recipient survival also was associated with PD (HR, 0.96; P < 0.05). Increased number of RRT modalities during the ESRD course was associated with increased risk for graft failure (HR, 1.04 per additional modality used; P < 0.005) and recipient death (HR, 1.11 per additional modality used; P < 0.001). Any combination or any single modality (except for PD + HD for graft survival and PD + HD and PD + HD + transplantation for recipient survival) had protective effects on graft and recipient survival compared with HD. CONCLUSION: Our results suggest that compared with PD, HD as an RRT modality immediately before transplantation or as a predominant RRT modality during the ESRD course, used alone or in combination with other RRT modalities, is associated with increased risks for graft failure and recipient death. Increased number of RRT modalities used during the ESRD course is associated with worsening of graft and recipient survival.

Mixed chimerism and immunosuppressive drug withdrawal after HLA-mismatched kidney and hematopoietic progenitor transplantation.

BACKGROUND: Rodents and dogs conditioned with total-lymphoid irradiation (TLI), with or without antithymocyte globulin (ATG), have been shown to develop mixed chimerism and immune tolerance without graft-versus-host disease (GVHD) after the infusion of major histocompatability complex (MHC)-mismatched donor bone marrow cells given alone or in combination with an organ allograft. METHODS: Four human leukocyte antigen (HLA)-mismatched recipients of living donor kidney transplants were conditioned with TLI and ATG posttransplantation and infused with cyropreserved donor granulocyte colony-stimulating factor (G-CSF) "mobilized" hematopoietic progenitor (CD34+) cells (3-5x10(6) cells/kg) thereafter. Maintenance prednisone and cyclosporine dosages were tapered, and recipients were monitored for chimerism, GVHD, graft function, T-cell subsets in the blood, and antidonor reactivity in the mixed leukocyte reaction (MLR). RESULTS: Three of the four patients achieved multilineage macrochimerism, with up to 16% of donor-type cells among blood mononuclear cells without evidence of GVHD. Prolonged depletion of CD4+ T cells was observed in all four patients. Rejection episodes were not observed in the three macrochimeric recipients, and immunosuppressive drugs were withdrawn in the first patient by 12 months. Prednisone was withdrawn from a second patient at 9 months, and cyclosporine was tapered thereafter. CONCLUSIONS: Multilineage macrochimerism can be achieved without GVHD in HLA-mismatched recipients of combined kidney and hematopoietic progenitor transplants. Conditioning of the host with posttransplant TLI and ATG was nonmyeloablative and was not associated with severe infections. Recipients continue to be studied for the development of immune tolerance.