FDA ALERT [06/11/2009]
The FDA has issued a warning about sirolimus. The FDA is notifying healthcare professionals of clinical trial data that suggest increased mortality in stable liver transplant patients after conversion from a calcineurin inhibitor (CNI)-based immunosuppressive regimen to sirolimus (Rapamune). The trial was conducted by sirolimus manufacturer, Wyeth.

As early as 2002, Wyeth issued a warning about not using sirolimus with liver transplantees.
Below is an excerpt from an article:

Nephrotoxicity is a serious adverse effect after liver transplantation often related to calcineurin inhibitors (CNI) with a incidence of 18.1% at 5 years. Sirolimus (SRL) is a new immunosuppressive drug that was introduced into solid organ transplant management in 1999. Herein we have performed a retrospective review of patients who developed renal insufficiency owing to CNI therapy after orthotopic liver transplantation.

CONCLUSION: calcineurin inhibitors CNIs may be associated with significant nephrotoxicity and chronic kidney damage. Patients who develop renal dysfunction after OLT [ liver transplant] may be successfully treated by an early switch from CNIs to SRL, stopping the progression toward chronic renal damage and preserving allograft survival.