Calcineurin inhibitor-free immunosuppression in kidney transplantation

The introduction of calcineurin inhibitors (CNI) revolutionized kidney transplantation (KTx). Exceptionally low acute rejection rates and excellent graft survival could be achieved with CNI-based (cyclosporine and tacrolimus) immunosuppressive protocols. However, despite short-term success, long-term graft attrition continues to be a significant problem, thus leaving clinicians looking for possible interventions. CNI nephrotoxicity is but one of numerous factors that may be contributing to long-term damage in transplant kidneys. Therefore, newer immunosuppressive agents such as mycophenolate mofetil and sirolimus (Rapa) have raised the possibility of withdrawing or avoiding CNIs altogether. Protocols exploring these options have gained greater attention over the last few years. Herein, we review studies addressing either CNI withdrawal or CNI avoidance strategies as well as discuss the risks versus benefits of these protocols. Given the accumulated experience to date, in our opinion, the use of CNIs as a part of immunosuppressive regimens remains the proven standard of care for renal transplant patients. The long-term safety and efficacy of CNI withdrawal and avoidance strategies need to be further validated in controlled clinical trials.

Toxicity-sparing protocols using mycophenolate mofetil in renal transplantation

The introduction of triple-therapy regimens that include a calcineurin inhibitor (CNI), steroids, and azathioprine greatly reduced the risk of acute rejection in renal transplantation. However, the long-term use of both CNIs and steroids is associated with serious toxicities that ultimately can impact patient/graft survival. Mycophenolate mofetil (MMF), a highly effective immunosuppressant with no known nephrotoxicity, has been shown to provide benefits in preserving long-term renal allograft function relative to azathioprine. For these reasons, MMF has become an integral component of toxicity-sparing maintenance regimens that seek to minimize patient exposure to CNIs and steroids. This paper provides an overview of current strategies for reducing the toxicities associated with these agents, which include both withdrawal and avoidance regimens with or without induction therapy. Data are accumulating that toxicity-sparing regimens involving MMF are safe and decrease the risk of side effects that accompany the use of CNIs and steroids. Future studies will determine how to best implement these regimens in the renal transplant population.