As part of the Spare-the-Nephron trial, we evaluated the combination mycophenolate mofetil (MMF) and sirolimus (SRL) as a calcineurin inhibitor (CNI)-free regimen for the preservation of renal function in renal allograft recipients. This 2-year, open-label, multicenter trial randomized 299 patients of which 151 were maintained on MMF and a CNI, 148 on MMF plus SRL (n=120, tacrolimus; n=31, cyclosporine). Baseline characteristics including measured (iothalamate) glomerular filtration rate (GFR) were similar between groups. After 1 year, the mean percentage change from baseline in the primary end point of measured GFR was significantly higher in the MMF/SRL group compared with the MMF/CNI group. After 2 years, the change was indistinguishable. Calculated creatinine clearance and GFR were significantly greater with MMF/SRL at 2 years within which biopsy-proven acute rejection (BPAR) occurred in 14 MMF/SRL-treated patients (3 graft losses) and in 17 receiving the MMF/CNI (6 graft losses). Significantly, no patients receiving MMF/SRL but five treated with MMF/CNI died. Thus, compared with MMF/CNI treatment, a 2-year regimen of MMF/SRL resulted in similar measures of renal function but with fewer deaths and a trend to less BPAR and graft loss.

This study suggests that a strategy consisting of a 50% CsA reduction is safe and is not associated with the increased risk of acute rejection observed in CsA withdrawal studies. It also has the potential to improve short-term allograft function and appears to reduce cardiovascular risk factors such as hypertension and hyperlipidemia.

In the Spare-the-Nephron (STN) Study, kidney transplant recipients randomized about 115 days posttransplant to convert from CNI (calcineurin inhibitor)/MMF to sirolimus (SRL)/MMF had a significantly greater improvement in measured GFR (mGFR) at 12 months compared with those kept on CNI/MMF. The difference at 24 months was not statistically significant. From 14 top enrolling centers, 128 of 175 patients identified with a functioning graft at 2 years consented to enroll in an observational, noninterventional extension study to collect retrospectively and prospectively annual follow-up data for the interval since baseline (completion of the parent STN study at 24 months posttransplant). Overall, 11 patients died, including 5 (7.6%) in the SRL/MMF group and 6 (9.7%) in the CNI/MMF group. Twenty-two grafts have been lost including 10 (15.2%) in the SRL/MMF arm and 12 (19.4%) in the CNI/MMF arm. Death and chronic rejection were the most common causes of graft loss in both arms. There were modestly more cardiovascular events in the MMF/SRL group. Estimated creatinine clearance (Cockcroft-Gault) from baseline out to 6 additional years (8 years posttransplant, ITT analysis, SRL/MMF, n = 34; CNI/MMF, n = 26) was 63.2 ± 28.5 mL/min/1.73 m in the SRL/MMF group and 59.2 ± 27.2 mL/min/1.73 m in the CNI/MMF group and was not statistically significant, but there is a clinically meaningful trend for improved long-term renal function in the SRL/MMF group compared with the CNI/MMF group. The long-term decision for immunosuppression needs to be carefully individualized.