Long-term results in renal transplant patients with allograft dysfunction after switching from calcineurin inhibitors to sirolimus

Background. Switching from calcineurin inhibitors (CNIs) to sirolimus might improve renal function in chronic renal transplant patients. Methods. In a prospective study, we assessed long-term efficacy and safety parameters in 43 renal transplant recipients who were switched from a CNI (cyclosporin A, 65%; and tacrolimus, 35%) to sirolimus for either chronic allograft dysfunction (n = 38) or recurrent cutaneous cancers (n = 5). A kidney biopsy was done in 79% of patients prior to conversion, and showed either chronic allograft nephropathy (n = 26) or CNI nephrotoxicity (n = 7). Conversion was either abrupt or progressive, with CNI withdrawal over 3 weeks. All patients also received steroids with or without mycophenolate mofetil or azathioprin. Patient data were recorded at baseline (D0), at 1 (D30) and 6 months (D180), and at 1, 1.5 and 2 years post-conversion. Results. After a mean post-conversion follow-up of 27 +/- 1.5 months, 58% of the patients were still on sirolimus. The survival of intent to treat patients and grafts was 95.3 and 93%, respectively. Overall, there was significant improvement in renal function, creatinine clearance increasing from 49.4 +/- 14.9 to 53 +/- 16.3 ml/min at D30 (P = 0.01), and to 54.7 +/- 20 ml/min at D180 (P = 0.01). Thereafter, creatinine clearance was not different from baseline, i.e. 54.7 +/- 21.7, 52.8 +/- 20 and 51.7 +/- 20.3 ml/min at years 1, 1.5 and 2, respectively. We divided the patients into two groups: responders (n = 29), those with an increase in creatinine clearance at 6 months post-conversion compared with D0, and non-responders (n = 14), those with a decrease in creatinine clearance at 6 months post-conversion compared with D0. In univariate analysis, factors predictive of response included proteinuria at D0 and the magnitudes of the differences between D30 and D0 for serum creatinine and lactate dehydrogenase. The conversion was associated with (i) significant decreases in serum calcium, phosphorus and uric acid, and in haemoglobin levels; (ii) significant increases in serum alkaline phosphatase, total cholesterol, parathyroid hormone, and the number of patients on statin and recombinant erythropoietin therapies; and (iii) the appearance of de novo proteinuria of > 1 g/day in 28% of patients (P < 0.0009), which was > 2 g/day in 12% of the entire cohort. Kidney biopsies in 17 patients 2 years after conversion showed the same Banff scores as observed at baseline. We identified three independent predictive factors for a renal response to the switch: absence of proteinuria, presence of antihypertensive therapy at D0 and serum lactate dehydrogenase level at D30. Conclusion. Conversion from CNIs to sirolimus in renal transplant patients with chronic allograft nephropathy was associated with improved renal function; however, 33% of the patients developed overt proteinuria.