Objectives: Tofacitinib is an oral JAK inhibitor for the treatment of rheumatoid arthritis (RA). We investigated concomitant methotrexate (MTX) dose on tofacitinib efficacy/safety in Japanese RA patients. Methods: This post hoc analysis pooled data from a 3-month phase 2 study (NCT00603512) and a 24-month phase 3 study (NCT00847613). Patients (N= 254) received tofacitinib (low-dose (1 or 3 mg), 5 mg, 10 mg) twice daily (BID) or placebo, with low-dose (>0 to 8 mg/week) or high-dose (>8 mg/week) MTX. Efficacy (ACR20/50/70 and DAS28-4 (ESR)<2.6 response rates; changes from baseline (CFB) in DAS28-4 (ESR) and HAQ-DI) and safety (adverse events (AEs), discontinuations due to AEs, serious AEs, and deaths) were assessed through month 3. Results: At month 3, ACR20/50/70 response rates, mean DAS28-4 (ESR) CFB and HAQ-DI CFB were similar across MTX doses and generally greater for all tofacitinib doses versus placebo. AE rates with low-dose/high-dose MTX were: placebo, 28.6%/52.9%; tofacitinib low-dose, 50.0%/66.7%; 5 mg BID, 56.5%/64.3%; 10 mg BID, 73.8%/67.7%. Conclusion: Tofacitinib efficacy in Japanese RA patients may be unaffected by background MTX dose. AE rates with low-dose versus high-dose MTX were lower with placebo, tofacitinib low-dose or 5 mg BID, but not 10 mg BID, with no apparent differences across system organ class/laboratory parameters.
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