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

Mizoribine Synchronized Methotrexate Therapy should be Considered when Treating Rheumatoid Arthritis Patients with an Inadequate Response to Various Combination Therapies

Objective The objective of this study was to confirm the efficacy of low-dose mizoribine (MZR), an inhibitor of inosine monophosphate dehydrogenase, as part of synchronized methotrexate (MTX) therapy for rheumatoid arthritis (RA) patients with an inadequate response to various combination therapies of MTX, other synthetic disease-modifying anti-rheumatic drugs (DMARDs) and biological DMARDs. Methods Low-dose MZR was administered to 56 uncontrolled RA patients being treated with MTX and various biological DMARDs. The observation period was 12 months, and the disease activity was evaluated based on the Disease Activity Score in 28 joints (DAS28)-ESR, Simplified Disease Activity Index (SDAI) and serum MMP-3 level. Results All of the disease activity indices were significantly improved within three months, and the serum MMP-3 levels were also significantly decreased around four months after starting low-dose MZR therapy. No patients experienced any adverse effects. Conclusion The present preliminary findings suggest that low-dose MZR therapy with MTX should be considered for the treatment of RA patients with an inadequate response to various combination therapies including MTX, other synthetic DMARDs and biological DMARDs or in whom increasing the dose of MTX is difficult for reasons such as adverse effects and complications.

Chronopharmacology of mizoribine in collagen-induced arthritis rats

We previously reported that higher therapeutic effects were obtained in rheumatoid arthritis (RA) patients and RA model animals when the dosing-times of methotrexate and tacrolimus were chosen according to the 24-h rhythms of the inflammatory response. Mizoribine (MZR) is an immunosuppressive agent and is used against RA in the same manner as methotrexate and tacrolimus. In this study, we examined whether a dosing-time dependency of the therapeutic effect of MZR could be detected in collagen-induced arthritis (CIA) rats. To measure C-reactive protein (CRP) and tumor necrosis factor (TNF)-α levels, blood was collected from CIA rats at different times. MZR was administered at two different dosing-times based on these findings and its effects and toxicity were examined. CRP and TNF-α concentrations in blood showed significant 24-h rhythms. The exacerbation of arthritis and excessive increase in leukocytes in CIA rats were markedly lower in the group treated with MZR at the dark phase than those of the group treated with MZR at the light phase. These findings suggest that the therapeutic index of RA therapy may be improved by administering MZR at a time in the day when the inflammatory reaction begins to activate.

Involvement of Multiple Transporters-mediated Transports in Mizoribine and Methotrexate Pharmacokinetics

Mizoribine is administered orally and excreted into urine without being metabolized. Many research groups have reported a linear relationship between the dose and peak serum concentration, between the dose and AUC, and between AUC and cumulative urinary excretion of mizoribine. In contrast, a significant interindividual variability, with a small intraindividual variability, in oral bioavailability of mizoribine is also reported. The interindividual variability is mostly considered to be due to the polymophisms of transporter genes. Methotrexate (MTX) is administered orally and/or by parenteral routes, depending on the dose. Metabolic enzymes and multiple transporters are involved in the pharmacokinetics of MTX. The oral bioavailability of MTX exhibits a marked interindividual variability and saturation with increase in the dose of MTX, with a small intraindividual variability, where the contribution of gene polymophisms of transporters and enzymes is suggested. Therapeutic drug monitoring of both mizoribine and MTX is expected to improve their clinical efficacy in the treatment of rheumatoid arthritis.

The effects of disease modifying anti-rheumatic drugs on osteoclastogenesis and bone destruction in rheumatoid arthritis

Finding the means to ameliorate and prevent bone destruction as well as control inflammation is an urgent issue in the treatment of rheumatoid arthritis (RA). Recently, it has been demonstrated that osteoclastogenesis plays an important role in the bone destruction and pathogenesis of RA. Here, we review the effects of disease modifying anti-rheumatic drugs (DMRAD) on the amelioration of bone destruction and osteoclastogenesis.

[Efficacy and safety of combination therapy with mizoribine and methotrexate for rheumatoid arthritis resistant with methotrexate]

Background. MZB is a purine analog, and is used as a disease modifying anti-rheumatic drug (DMARD). We conducted an open label uncontrolled clinical trial to evaluate the efficacy and safety of combination therapy with methotrexate (MTX) and mizoribine (MZB). Methods. Thirty one RA patients (9 males, 22 females, 68±12 year-old) who fulfilled ACR criteria of RA and did not show sufficient clinical response to MTX were included. MZB (150 mg/day, once a day) were added to MTX. DAS28-CRP was measured at day 0 and 1, 3, 6, and 12 months after the treatment. Adverse events were recorded. Results. Overall DAS28-CRP was significantly decreased from 4.4±1.0 to 3.1±1.3 at 3 months (p<0.01), 2.7±0.68 at 6 months (p<0.01), 2.4±1.4 at 12 months (p<0.01). Seventeen patients (55%) achieved significant improvement of DAS28-CRP. Number of swollen joints of responders before the treatment was significantly fewer than that of non-responders. Improvement of DAS28-CRP was significantly different between the responders (0.91±0.74) and non-responders (0.18±0.66) at 1 month (p<0.01). Nine patients (29%) could achieve remission Four patients experienced adverse events. Conclusions. MTX and MZB combination therapy was effective and relatively safety.

Efficacy and safety of single-dose mizoribine for patients with rheumatoid arthritis: results at 6 months after switching from a multiple-dose regimen without a change in total daily dose

To determine the efficacy and safety of single-dose mizoribine (MZR) for patients with rheumatoid arthritis (RA), a 6-month, single-arm, open-label, prospective observation study was performed. In patients who had been taking MZR at 100-150 mg/day in 2-3 divided portions continuously for at least 3 months, and who had shown a lack of clinical response, or escape (defined as a lack of response at the time of switching, even if some form of response had been shown before that), multiple-dose administration was switched to single-dose administration without changing the total daily dose. Efficacy was assessed in terms of the disease activity score, using the 28-joint count and erythrocyte sedimentation rate (DAS 28-ESR). Of the 34 enrolled patients, 28 met all the eligibility criteria and were assessed for efficacy, and finally 26 patients were able to receive the single-dose regimen throughout the full 6 months. The DAS28-ESR showed a significant decrease from 2 months after switching, and 46.4% of the 28 patients finally achieved a good or moderate response (3 and 10 patients, respectively). With regard to safety, no serious adverse events were observed. In conclusion, the administration of MZR at 100 or 150 mg in a single dose is thought to be a useful alternative form of MZR therapy.

Efficacy and safety of mizoribine by one single dose administration for patients with rheumatoid arthritis

OBJECTIVE

Mizoribine (MZR) is an immunosuppressant that inhibits nucleic acid metabolism and is a relatively safe disease-modifying anti-rheumatic drug (DMARD). We evaluated the efficacy and safety of one single dose per day for patients with rheumatoid arthritis (RA).

PATIENTS AND METHODS

In this study 32 patients with RA received MZR therapy. We evaluated the average dose of MZR and prednisolone, response to treatment and peak plasma level of MZR.

RESULTS

The average dose of MZR was 146.1±31.2 (range: 50-200) mg/day. The average dose of prednisolone was 4.63±3.59 (range: 0-14) mg/day. The average plasma level of MZR, measured after 3 hours, was 2.20±0.49 µg/mL in the responder group and 1.59±0.82 µg/mL in the non-responder group (p=0.020). The treatment with MZR for 24 weeks was completed by 71.9% of patients and the proportion of patients who achieved a good and moderate response rate according to the European League Against Rheumatism (EULAR) criteria was 56.3% at 24 weeks. The plasma level of MZR which was greater than or equal to 2.12 µg/mL was significantly correlated with the clinical response (p<0.01). Only one of thirty-two cases discontinued the treatment, because of skin eruption.

CONCLUSION

This study included patients that could not be treated with other DMARDs and/or biologic agents because of age, interstitial pneumonia and other complications. We show that MZR may be a useful and relatively safe therapy for patients in this group.