The Efficacy and Safety of Clazakizumab, an Anti–Interleukin‐6 Monoclonal Antibody, in a Phase IIb Study of Adults With Active Psoriatic Arthritis

To evaluate the efficacy of clazakizumab, a monoclonal antibody with high affinity and specificity for the interleukin-6 (IL-6) cytokine, in psoriatic arthritis (PsA).In this randomized, double-blind, placebo-controlled, dose-ranging study (ClinicalTrials. gov identifier: NCT01490450), patients with active PsA and an inadequate response to nonsteroidal antiinflammatory drugs were randomized (1:1:1:1) to receive subcutaneous placebo or clazakizumab 25 mg, 100 mg, or 200 mg every 4 weeks, with or without methotrexate. The primary end point was the response rate according to the American College of Rheumatology 20% criteria for improvement (ACR20) at week 16, with secondary efficacy end points at weeks 16 and 24.A total of 165 patients were randomized. At week 16, the ACR20 response rate was significantly higher with clazakizumab 100 mg versus placebo (52.4% versus 29.3%; P = 0.039). ACR20 response rates at week 16 were 46.3% with clazakizumab 25 mg (P = 0.101 versus placebo) and 39.0% with clazakizumab 200 mg (P = 0.178 versus placebo). ACR50/ACR70 response rates were numerically higher with clazakizumab versus placebo at weeks 16 and 24. Compared with placebo, clazakizumab treatment significantly improved musculoskeletal manifestations (joint signs and symptoms, enthesitis, and dactylitis), with minimal improvements in skin disease, without clear evidence of a dose response. Clazakizumab was well tolerated.This is the first clinical trial of an IL-6-targeted therapy in PsA. Clazakizumab may be an effective treatment option for musculoskeletal aspects of PsA, but because of the lack of a dose response in this study, further studies are required to confirm the appropriate dose. The safety profile is consistent with the pharmacology of IL-6 blockade and prior clinical experience with this antibody in rheumatoid arthritis.