The goal of this study was to determine the efficacy and safety of low-dose mizoribine -pulse therapy in combination with methotrexate in rheumatoid arthritis patients with an insufficient response to methotrexate.
    Methods: Our study was retrospectively conducted. A total of 37 patients with rheumatoid arthritis, who showed an inadequate response to methotrexate, were given mizoribine in combination with methotrexate. Patients first received 100mg and later 150mg of mizoribine together with methotrexate. We evaluated clinical improvements in the disease activity score (DAS28CRP) using the European League against Rheumatism (EULAR) criteria. In addition to the good response and moderate response rates, the LUNDEX were calculated.
    Results: thirty-five patients (95%) were given a dosage 150mg of mizoribine every time. Outcomes were continuation of treatment in 10 patients (27.0%), termination of treatment due to inefficacy in 25 patients (67.6%), termination of treatment for toxicity in no patients, and 2 other patients (5.4%). The good response and moderate response rates and the LUNDEX corrected responses were 28% and 24% at one month, 36% and 35% at 2 months, 36% and 25% at 3 months, 35% and 22% at 4 months, 43% and 20% at 5 months, and 43% and 21% at 6 months, respectively.
    Conclusion: Low-dose mizoribine pulse therapy in combination with methotrexate in patients with rheumatoid arthritis is well tolerated. That therapy should be investigated for those who are poorly controlled by methotrexate and for whom the use of biologic treatment was impossible.