Objective. Clazakizumab is a humanized monoclonal antibody that binds to the interleukin-6 (IL-6) cytokine. This study was undertaken to evaluate the efficacy and safety of clazakizumab in combination with methotrexate (MTX) or clazakizumab monotherapy versus MTX alone in patients with rheumatoid arthritis (RA) and an inadequate response to MTX. Methods. In this multinational, phase IIb, randomized, double-blind, placebo-controlled, dose-ranging study, patients were randomized to receive 1) oncemonthly subcutaneous (SC) clazakizumab at 25, 100, or 200 mg plus MTX, 2) once-monthly SC clazakizumab at 100 mg or 200 mg as monotherapy, or 3) MTX plus placebo (i.e., MTX alone). Adalimumab (40 mg) plus MTX was included as an active reference. The primary end point was the American College of Rheumatology 20% (ACR20) improvement response rate at week 12. Secondary end points included ACR20, ACR50, and ACR70 response rates as well as protocol-defined remission rates and Health Assessment Questionnaire disability index scores at weeks 12 and 24. Results. In total, 418 patients were randomized, and baseline characteristics were balanced across the treatment groups. Patients receving clazakizumab had significantly greater ACR20 response rates at week 12 compared with patients receiving MTX alone (76.3%, 73.3%, and 60.0% of patients in the clazakizumab 25, 100, and 200 mg plus MTX groups, respectively, and 55.0% and 61.0% of patients in the clazakizumab 100 and 200 mg monotherapy groups, respectively, versus 39.3% of patients receiving MTX alone; P < 0.05 for all comparisons). At week 24, all clazakizumab groups had higher ACR20, ACR50, and ACR70 response rates and higher remission rates compared with MTX alone. Rates of serious adverse events ranged from 8.3% to 13.6% in the clazakizumab treatment groups, compared with 3.3% in the MTX alone group. Changes in laboratory data were consistent with the pharmacologic effects of IL-6 blockade. Conclusion. In patients with RA and an inadequate response to MTX, treatment with clazakizumab in combination with MTX or clazakizumab monotherapy was well tolerated, and patients achieved significant improvements in disease activity, including higher rates of remission, as compared with patients receiving MTX alone.
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