Introduction: There is insufficient evidence regarding the appropriate dose of methotrexate (MTX) required to achieve specific treatment goals in patients with rheumatoid arthritis (RA) receiving biologic drugs in Japan. The present study aimed to assess the dose-response effect of MTX in combination with adalimumab (ADA) to achieve low disease activity (LDA) and/or remission at 24 weeks in RA patients.
Methods: This analysis used data of the ADA all-case survey in Japan (n = 7740), and 5494 patients who received ADA and MTX were classified into five groups by weighted average MTX dose (>0-<4, 4-<6, 6-<8, 8-< 10, and ≥10 mg/week). Of the 5494 patients, 3097 with baseline 28-joint disease activity score based on erythrocyte sedimentation rate >3.2 were analyzed for effectiveness by MTX dose.
Results: In biologic-naïve patients (n = 1996/3097), LDA/remission rates increased with MTX up to 6-<8 mg/week and then plateaued at higher doses (LDA, p = 0.0440; remission, p = 0.0422). In biologic-exposed patients (n = 1101/3097), LDA/remission rates increased with MTX dose (LDA, p = 0.0009; remission p = 0.0143). The incidences of serious adverse drug reactions (ADRs) and serious infections did not differ by MTX dose, but total ADRs and infections were significantly higher (p < 0.05) with increased MTX doses.
Conclusion: The appropriate MTX doses in combination with ADA to achieve LDA and/or remission at week 24 were different between biologic-naïve and biologic-exposed patients with RA, suggesting that 8 mg/week of MTX would be enough for biologic-naïve patients.
Trial registration: ClinicalTrials.gov identifier, NCT01076959.
Funding: AbbVie and Eisai Co., Ltd.
Keywords: Adalimumab; Doses; Effectiveness; Methotrexate; Rheumatoid arthritis; Safety.