Randomized comparative trial of mizoribine versus mycophenolate mofetil in combination with tacrolimus for living donor renal transplantation

Mizoribine (MZR) was approved in 1984 in Japan for the suppression of rejection in renal transplantation with an approved administration dosage of 1-3 mg/kg/day. The action of MZR resembles that of mycophenolate mofetil (MMF), but MZR dosing is markedly lower than that of MMF. To examine whether higher dosing of MZR could obtain efficacy similar to MMF in renal transplantation, we conducted a comparative study of MZR and MMF using a high daily dose of MZR. A prospective, randomized comparative study of MZR versus MMF using tacrolimus (FK) and steroids as the base was conducted in 35 patients who had undergone living-donor renal transplantation (ABO-incompatible patients were not included) at 8 institutions in Japan between July 2005 and June 2007. Starting doses were 12 mg/kg/day for MZR and 2 g/day for MMF. Dosages of FK and steroids were set according to the protocol of each institution. Patient and graft survival rate at 1 year after transplantation was 100 % in each group, with no significant difference in rejection rate apparent between groups. Adverse events found in both groups were characteristic, frequently involving infection and digestive organ disorder in the MMF group and elevated uric acid levels in the MZR group. Based on these results, MZR and MMF are considered almost equivalent in terms of efficacy and safety.