Albuminuria after renal transplantation: maintenance with sirolimus/low-dose tacrolimus vs. mycophenolate mofetil/high-dose tacrolimus

A Randomized 2x2 Factorial Clinical Trial of Renal Transplantation: Steroid-Free Maintenance Immunosuppression with Calcineurin Inhibitor Withdrawal after Six Months Associates with Improved Renal Function and Reduced Chronic Histopathology

INTRODUCTION

The two most significant impediments to renal allograft survival are rejection and the direct nephrotoxicity of the immunosuppressant drugs required to prevent it. Calcineurin inhibitors (CNI), a mainstay of most immunosuppression regimens, are particularly nephrotoxic. Until less toxic antirejection agents become available, the only option is to optimize our use of those at hand.

AIM

To determine whether intensive rabbit anti-thymocyte globulin (rATG) induction followed by CNI withdrawal would individually or combined improve graft function and reduce graft chronic histopathology-surrogates for graft and, therefore, patient survival. As previously reported, a single large rATG dose over 24 hours was well-tolerated and associated with better renal function, fewer infections, and improved patient survival. Here we report testing whether complete CNI discontinuation would improve renal function and decrease graft pathology.

METHODS

Between April 20, 2004 and 4-14-2009 we conducted a prospective, randomized, non-blinded renal transplantation trial of two rATG dosing protocols (single dose, 6 mg/kg vs. divided doses, 1.5 mg/kg every other day x 4; target enrollment = 180). Subsequent maintenance immunosuppression consisted of tacrolimus, a CNI, and sirolimus, a mammalian target of rapamycin inhibitor. We report here the outcome of converting patients after six months either to minimized tacrolimus/sirolimus or mycophenolate mofetil/sirolimus. Primary endpoints were graft function and chronic histopathology from protocol kidney biopsies at 12 and 24 months.

RESULTS

CNI withdrawal (on-treatment analysis) associated with better graft function (p <0.001) and lower chronic histopathology composite scores in protocol biopsies at 12 (p = 0.003) and 24 (p = 0.013) months, without affecting patient (p = 0.81) or graft (p = 0.93) survival, or rejection rate (p = 0.17).

CONCLUSION

CNI (tacrolimus) withdrawal at six months may provide a strategy for decreased nephrotoxicity and improved long-term function in steroid-free low immunological risk renal transplant patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00556933.

A randomized 2×2 factorial trial, part 1: single-dose rabbit antithymocyte globulin induction may improve renal transplantation outcomes

Supplemental digital content is available in the text.

Background

We conducted a randomized and unblinded 2×2 sequential-factorial trial, composed of an induction arm (part 1) comparing single-dose (SD) versus divided-dose rabbit antithymocyte globulin (rATG), and a maintenance arm (part 2) comparing tacrolimus minimization versus withdrawal. We report the long-term safety and efficacy of SD-rATG induction in the context of early steroid withdrawal and tacrolimus minimization or withdrawal.

Methods

Patients (n=180) received 6 mg/kg rATG, SD or four alternate-day doses (1.5 mg/kg/dose), with early steroid withdrawal and tacrolimus or sirolimus maintenance. After 6 months targeted maintenance levels were tacrolimus, 2 to 4 ng/mL and sirolimus, 4 to 6 ng/mL or, if calcineurin inhibitor–withdrawn, sirolimus 8 to 12 ng/mL with mycophenolate mofetil 2 g two times per day. Primary endpoints were renal function (abbreviated modification of diet in renal disease) and chronic graft histopathology (Banff). Secondary endpoints included patient survival, graft survival, biopsy-proven rejection, and infectious or noninfectious complications.

Results

Follow-up averaged longer than 4 years. Tacrolimus or sirolimus and mycophenolate mofetil exposure was identical between groups. The SD-rATG associated with improved renal function (2-36 months; P<0.001) in deceased donor recipients. The SD-rATG associated with quicker lymphocyte, CD4 T cell, and CD4-CD8 recovery and fewer infections. Cox multivariate hazard modeling showed divided-dose–rATG (P=0.019), deceased donor (P=0.003), serious infection (P=0.0.018), and lower lymphocyte count (P=0.001) associated with increased mortality. Patients with all four covariates showed a 27-fold increased likelihood of death (P=0.00002). Chronic graft histopathology, rejection rates, and death-censored graft survival were not significantly different between groups.

Conclusion

The SD-rATG induction improves the 3-year renal function in recipients of deceased donor kidneys. This benefit, along with possibly improved patient survival and fewer infections suggest that how rATG is administered may impact its efficacy and safety.

Clinical significance of proteinuria at posttransplant year 1 in kidney transplantation

PURPOSE

Proteinuria in the nontransplant population is a progressive renal disease. We analyzed the prevalence and clinical significance of proteinuria as well as factors related to its degree at posttransplant year 1 among kidney transplant recipients.

METHODS

We measured protein in a 24-hour urine among 644 recipients from January 1996 to December 2010.

RESULTS

Among 372 male and 272 female recipients, the mean amount of urinary protein was 424.4 ± 1010 mg/d (range, 13.88-8691) including 388 (60.2%) subjects with microproteinuria and the other 256 (39.8%) with overt proteinuria. Nephrotic range proteinuria was observed in 17 (2.6%) and nonnephritic range proteinuria, in 239 (37.1%) recipients. The latter cohort was categorized into low-grade proteinuria (n = 224; 34.8%) and high-grade proteinuria (n = 15; 2.3%). Proteinuria at posttransplant 1 year highly correlated with serum creatinine values at posttransplant years 1 and 2 as well as estimated glomerular filtration rate but not creatinine clearance at postoperative year 2. A greater incidence of graft loss was observed among recipients with more severe proteinuria. Males, recipients with anti-hepatitis C virus antibody, unrelated donors, anti-thymocyte immunoglobulin at the time of reperfusion, maintenance immunosuppression with cyclosporine or without mycophenolate mofetil were strongly associated with the amount of proteinuria.

CONCLUSION

This study demonstrated the prevalence of proteinuria in kidney transplant recipient to be high. The presence as well as level of proteinuria were predictive markers for inferior allograft function.