Introduction. This study examines the efficacy and toxicity of sirolimus used as primary immunosuppression in combination with reduced dose tacrolimus (calcineurin inhibitor [CI]-sparing regimen) or mycophenolate mofetil (CI-free regimen) in high-risk cadaveric renal transplantation. Methods. Seventy subjects were treated in a quadruple sequential protocol in which 41 were treated with a CI-sparing regimen and 29 were treated with a CI-free regimen. The efficacy and toxicity profiles of these regimens were prospectively monitored and compared. Results. The study consisted of African Americans (71%), cadaveric donors (100%), donors aged more than 50 years (30%), and patients with delayed graft function (47%). At 1 year, patient survival, graft survival, and incidence of biopsy-proven acute rejection were 98%, 80%, and 10%, respectively, in the CI-sparing group and 100%, 89%, and 7%, respectively, in the CI-free group. Three-month protocol biopsies were performed in 41% (17/41) and 67% (20/29) of the subjects in the CI-sparing and CI-free groups, respectively. Subclinical rejection was detected in 6% (1/17) and 15% (3/20) of the subjects in the CI-sparing and CI-free groups, respectively. Histologic evidence of chronic allograft nephropathy was more prevalent in the CI-sparing group. At 1 year, the mean estimated creatinine clearance was higher in the CI-free group than in the CI-sparing group (72.4±20.0 mL/min vs. 50.5±20.8 mL/min, P<0.01). The two regimens had similar toxicity profiles (hospital readmission, infection, wound complications, and metabolic complications). Conclusions. Both sirolimus-based CI-sparing and CI-free regimens are safe and effective in a population with high immunologic risk. The CI-free regimen is associated with better renal function at 1 year post-transplant. Long-term follow-up will aid in determining the risk and benefit ratio of these regimens.
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