Efficacy of mizoribine pulse therapy in patients with rheumatoid arthritis who show a reduced or insufficient response to infliximab

The efficacy of infliximab, a chimeric antibody against tumor necrosis factor-α used to treat patients with rheumatoid arthritis (RA), tends to decrease as patients develop human antichimeric antibody against infliximab (HACA). The clinical study reported here was designed to evaluate the efficacy of mizoribine (MZR) pulse therapy in patients who show a reduced or insufficient response to infliximab. Ten RA patients who had active arthritis despite infliximab therapy were treated with MZR pulse therapy at a dose of 100 mg MZR and methotrexate (MTX) and the disease activity assessed at baseline and at weeks 4–8, 12–16, and 20–24. The dose was increased to 150 mg in those patients who showed an insufficient response to MZR. The mean 28-joint disease activity score (DAS28) at weeks 12–16 and 20–24 of therapy was significantly lower than that at baseline. A moderate or good European League against Rheumatism (EULAR) response was achieved in seven patients (70%) at weeks 12–16 and in five patients (50%) at weeks 20–24. The dose of 150 mg MZR was effective in one of the three patients who showed an insufficient response to pulse therapy with 100 mg MZR. Based on these results, we propose that MZR pulse therapy should be attempted before the patient is switched to other biologics.