A Japanese multicenter study of high-dose mizoribine combined with cyclosporine, basiliximab, and corticosteroid in renal transplantation (the fourth report).

We examined the efficacy and safety of 4-drug combination therapy using high-dose mizoribine (MZR) (8 mg/kg/d), cyclosporine (CsA), basiliximab (BXM), and steroid (STR) in 39 renal transplant recipients. Acute rejection episodes (ARE), which occurred in 9 (23.1%) patients, correlated with lower blood levels of MZR (trough levels ≥ 2 µg/mL). In addition, lower MZR concentrations tended to be associated with a higher incidence of rejection episodes in children aged ≤ 10 years than in those aged ≥ 11 years. The area under the received operating characteristics (ROC) curve of MZR trough level to pred ARE was 0.825 (95% confidence interval, 0.690-0.962; P = .002). Based on the ROC analysis, are MZR cut-off of 1.6 µg/mL showed a sensitivity of 81.8% and a specificity of 75.0%. Adverse events were observed in 23 patients, including infections in 11 (7 patients positive for cytomegalovirus [CMV] antigen and 4 treated with anti-CMV drugs). The MZR trough levels seemed to be higher among patients with adverse events than in those free of them, but it was no significant. All patients experienced successful engraftment except 1 who died of unknown cause with a functioning graft. In conclusion, our study showed that low MZR trough levels correlated with the incidence of ARE. No serious adverse effects were encountered with this therapy.