Objective: To evaluate the efficacy and safety of sirukumab, a human anti-interleukin six monoclonal antibody, in Japanese patients with rheumatoid arthritis who were refractory to anti-tumor necrosis factor therapy. Methods: This subgroup analysis, based on a double-blind, placebo-controlled, 52-week phase 3, global study (SIRROUND-T) assessed the American College of Rheumatology (ACR) 20 response at week 16 (primary endpoint). Secondary endpoints: ACR 50, Disease Activity Score in 28 joints-C reactive protein, Health Assessment Questionnaire-Disability Index and safety were assessed. Results 116/878 patients received sirukumab 50 mg/4 weeks (q4w, n = 35), 100 mg/2 weeks (q2w, n = 44) or placebo (n = 37) subcutaneously. Significantly more patients achieved ACR 20 response at week 16 with sirukumab (50 mg q4w:20 [57.1%]; p <.001, 100 mg q2w:24 [54.5%]; p =.001) versus placebo (7 [18.9%]); consistent significant improvement in secondary endpoints at week 24 and 52 was observed. At week 24, incidence of treatment-emergent adverse events (TEAEs) was numerically higher with sirukumab groups (50 mg q4w:29 [82.9%]; 100 mg q2w:38 [86.4%] versus placebo (28 [75.7%]); however, at week 52, sirukumab combined groups had comparable incidence of TEAEs. Conclusion: Efficacy findings through 52 weeks were comparable between sirukumab doses in Japanese patients and consistent with primary SIRROUND-T study results. No new safety signals were observed.
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