Sirolimus therapy following early cyclosporine withdrawal in transplant patients: mechanisms of action and clinical results

Cyclosporine (CsA), a member of the family of calcineurin inhibitors, is a cornerstone of the immunosuppressive treatments used after organ transplantation. However, it exhibits significant toxicity, including nephrotoxicity and increased cardiovascular risk factors. CsA withdrawal has been used as a strategy to improve renal allograft function and other CsA-related toxicities. In order to maintain adequate immunosuppression levels, sirolimus may be used in association with CsA withdrawal. Sirolimus is a member of the mammalian target of rapamycin (mTOR) family. It presents a good immunosuppressive efficacy associated with antiproliferative actions. Early withdrawal of CsA with sirolimus is associated with a significant improvement of renal function. Despite numerically a higher incidence of acute rejection episodes, this maneuver seems also to be associated with a better allograft survival in the long-term, and improvement of renal histology and blood pressure. However, CsA withdrawal is only feasible in a selected population. Furthermore, the use of sirolimus is associated with other side-effects including lipid abnormalities, abnormal liver tests, and thrombocytopenia. Other studies are mandatory to define the population who can benefit from this maneuver. Finally, complete CsA avoidance has been already reported and is currently under clinical investigation.