Low dose of mycophenolate mofetil is enough in desensitized kidney transplantation using rituximab.

BACKGROUND: Rituximab is widely used in kidney transplantation. However, it is not clear whether the conventional doses of maintenance immunosuppressant in rituximab-treated kidney transplantation (KT) are appropriate. In our previous study, decreasing mycophenolate mofetil (MMF) dose due to infection did not increase the incidence of rejection or graft failure. Based on these experiences, we developed a new protocol with a lower dose of MMF and studied its clinical outcomes in rituximab-treated KT.

METHODS: We enrolled all patients who underwent ABO-incompatible or human leukocyte antigen (HLA)-sensitized living donor KT with the new immunosuppressant protocol after preconditioning with rituximab, but without splenectomy from November 2011 to May 2013. Seventy-two patients (group 1) were consecutively enrolled in this study and followed until November 2013. Patients from our previous study served as control groups. Sixty-seven patients received KT using rituximab with a conventional dose of MMF (group 2), and 87 patients received ABO compatible KT without need for rituximab (group 3). Clinical outcomes, including rejection, infection, and graft survival, were compared between the groups. The χ (2) test and Fisher's exact test were used for categorical variables, the Student's t-test and Mann-Whitney U test were used for continuous variables, and a log-rank test was used for mortality analysis.

RESULTS: Doses of postoperative MMF (g/day) were lower in group 1 than in the other groups (1.03 ± 0.19, 1.48 ± 0.34 and 1.48 ± 0.32 g/day at 1 week, p < 0.001). Infectious complications occurred more often in groups with conventional MMF doses (group 2 and 3) than in group 1 (16.7 vs. 37.3 %, p = 0.007 and 16.7 vs. 34.5 %, p = 0.012, respectively). Notably, group 1 showed a lower incidence of cytomegalovirus infection than group 2. However, reduction in MMF dose did not increase the incidence of acute rejection (4.2, 4.5 and 10.3 %). Only one graft failure occurred in group 2 due to vessel kinking after operation. There were no significant differences in the incidence of malignancy and mortality between groups.

CONCLUSIONS: A low MMF dose reduces infection without increasing rejection or graft loss and it may be appropriate to reduce the dose of MMF for rituximab-treated KT patients.