Effects of low-dose mizoribine pulse therapy in combination with methotrexate in rheumatoid arthritis patients with an insufficient response to methotrexate

The aim was to determine the efficacy of low-dose intermittent pulse administration of mizoribine (MZR), a purine synthesis inhibitor, in combination with methotrexate (MTX) to control the symptoms of rheumatoid arthritis (RA) in patients with an insufficient clinical response to MTX alone. Twenty-seven patients with active RA, despite treatment with MTX, were enrolled and given MZR in combination with MTX and continued for 24 weeks. The primary endpoint was assessment of clinical improvements using the European League against Rheumatism (EULAR) criteria. Administering MZR to RA patients with an insufficient response to MTX produced significant improvements in the Disease Activity Score 28 (DAS28) after 8–24 weeks. In addition, after 24 weeks, 60.0% and 8.0% of patients had achieved moderate and good responses, respectively, and there were significant reductions in Modified Health Assessment Questionnaire and serum matrix metalloproteinase-3 levels. The present preliminary study suggests that low-dose MZR in combination with MTX is well tolerated and provides both clinical and economic benefits.