Acceptability and usefulness of mizoribine in the management of rheumatoid arthritis in methotrexate-refractory patients and elderly patients, based on analysis of data from a large-scale observational cohort study

Effectiveness and safety of Mizoribine for the treatment of IgG4-related Disease: A Retrospective Cohort Study

OBJECTIVE

Patients with IgG4-Related Disease (IgG4RD) usually require steroid-sparing agents due to relapse with tapering glucocorticoids (GC). The aim of this study was to determine the efficacy and safety of Mizoribine (MZR) among IgG4RD, which inhibits inosine monophosphate dehydrogenase, a rate-limiting enzyme in the de novo pathway of purine synthesis.

METHODS

We retrospectively reviewed records of IgG4RD patients at the Immuno-Rheumatology Center in St. Luke's International Hospital, Tokyo, Japan. Patients were classified into the MZR combination group, and those treated with GCs alone or with other immunosuppressants were included in the control group. Disease exacerbation, GC dose, IgG-IgG4 titre, and adverse events were evaluated using univariate analyses, including the Kaplan-Meier method. The Cox proportional hazard model was used to evaluate risk factors for exacerbation.

RESULTS

A total of 14 and 29 cases were included in the MZR combination and control groups, respectively. Multiple organ involvement (≥3 organs) was significantly more frequent in the MZR combination treatment group (10 [71.4%] vs 9 [31.0%], p= 0.021). Kaplan-Meier analysis revealed a significant reduction in exacerbation in patients with multiple organ involvement (p< 0.001), but not in total (p= 0.42). The adjusted hazard ratios of MZR use and multiple organ involvement for exacerbation were 0.34[0.12-1.01] (p= 0.052), and 3.51[1.29-9.51] (p= 0.014). The cumulative GC dose tended to be lower in the MZR combination group (1448[1003, 1642] vs 2179[1264, 3425]; p= 0.09).

CONCLUSION

MZR showed a significant steroid-sparing effect and decrease in exacerbation among IgG4RD patients with multi-organ involvement. MZR could be a treatment option for IgG4RD.

Medical care costs of patients with rheumatoid arthritis during the prebiologics period in Japan: a large prospective observational cohort study

Our objective was to describe outpatient medical care costs of patients with rheumatoid arthritis (RA) in the prebiologics period in Japan. The outpatient costs of 6,771 RA patients (17,666 patient years) who were enrolled in an observational cohort study at the Institute of Rheumatology, Rheumatoid Arthritis (IORRA), in Tokyo, Japan, were calculated from the billing records dated from 2000 to 2004. Associations between outpatient costs and variables such as age, RA duration, RA disease activities, and disability levels were assessed. The average outpatient cost gradually increased (+7.7% in 4 years) from 271,498 JPY per year in 2000 to 292,417 JPY per year in 2004. Medications accounted for approximately 50% of total outpatient costs, which increased 29.6% during the 4 years. The outpatient costs increased in association with aging, longer RA duration, higher Disease Activity Score of 28 Joints (DAS28), and higher Japanese version of Health Assessment Questionnaire (J-HAQ) score. Generalized linear regression analysis revealed that both DAS28 and J-HAQ scores were the most significant factors associated with outpatient costs (p < 0.001). Outpatient costs for patients with RA increased year after year over the 4-year period under observation in Japan. Medical costs were higher with increasing RA disease activity and disability levels.

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.

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-alpha 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.

A sudden onset of diabetic ketoacidosis and acute pancreatitis after introduction of mizoribine therapy in a patient with rheumatoid arthritis

Mizoribine has been recognized to have an acceptable toxicity profile compared with other immunosuppressants. In this study, however, we report a case of diabetic ketoacidosis and acute pancreatitis that suddenly occurred in a rheumatoid arthritis patient 2 weeks after introduction of mizoribine therapy. To the best of our knowledge, this is the first case in the literature to show mizoribine-induced diabetic ketoacidosis. Through prompt diagnosis and treatment, the patient recovered from these extremely rare but potentially lethal complications.