Randomized trial comparing late concentration-controlled calcineurin inhibitor or mycophenolate mofetil withdrawal.

Background: Early calcineurin inhibitor (CNI) withdrawal with mycophenolate mofetil (MMF) has not become routine practice, due to concerns about excess acute rejection. Therapeutic drug monitoring may be advantageous when the CNI or MMF is withdrawn.

Methods: This prospective, randomized, concentration-controlled withdrawal study enrolled 177 stable renal transplant recipients on maintenance CNI-based immunosuppression, combined with steroids and MMF. After the feasibility phase of the study, patients were randomized to MMF-withdrawal (target area under the time-concentration curve-cyclosporine: 3250 ng·hr/mL or tacrolimus: 120 ng·hr/mL) or CNI-withdrawal (target area under the time-concentration curve-mycophenolic acid: 75 μg·hr/mL).

Results: The estimated glomerular filtration rate (modification of diet in renal disease) remained significantly better after CNI elimination (59.5±2.1 mL/min vs. 51.1±2.1 mL/min, P = 0.006) up to 3 years and resulted in less functional decline, including the subgroup with an estimated glomerular filtration rate less than 50 mL/min at baseline (P = 0.03). At 6 months, one patient in the MMF-withdrawal group (1.3%) and three in the CNI-withdrawal group (3.8%) experienced acute rejection (P = 0.62). The defined higher mycophenolic acid exposure was well tolerated.

Conclusion: These data indicate that with time the large majority of stable renal transplant recipients can be safely reduced to dual therapy with MMF or CNIs, applying concentration-controlled dosing. CNI-free patients, including those with moderate renal allograft dysfunction, have the benefit of improved renal function, whereas the risk of acute rejection after late withdrawal is low.