Safety and immunologic benefits of conversion to sirolimus in kidney transplant recipients with long-term exposure to calcineurin inhibitors

BACKGROUND/AIMS: Sirolimus (SRL) is a promising immunosuppressant replacingcalcineurin inhibitors (CNIs). This study was performed to evaluate the safetyand immunologic benefits of conversion to SRL in stable kidney transplant (KT)recipients exposed to CNIs for long periods. METHODS: Fourteen CNI-treated KT recipients with stable renal function for morethan 10 years were included. Either 2 or 3 mg per day of SRL was administeredwhile CNIs were reduced by half starting on day 1, and then stopped 2 weeks afterSRL introduction. The safety of SRL conversion was assessed considering thegraft function, acute rejection, and graft loss. Immunologic alterations were measuredvia serial changes of T cell and B cell subsets after SRL conversion. Adverseeffects of SRL conversion were also evaluated. RESULTS: Conversion to SRL was successful in nine patients (64.2%). Conversionto SRL preserved graft function as compared to the baseline value (p = 0.115). Noacute rejection or allograft loss was observed during the follow-up period. Immunemonitoring of T and B cells revealed a regulatory T cells increase after SRL conversion (p = 0.028). Most adverse events developed within 6 weeks after SRLconversion, and oral mucositis was the main cause of SRL withdrawal. CONCLUSIONS: Conversion to SRL can be safe and has immunologic benefits in KTrecipients with long-term CNI exposure. Close monitoring of mucocutaneous adverseevents is, however, required in the early period after SRL conversion.