Arthritis & Rheumatology. 2015 Jul 2. doi: 10.1002/art.39249. [Epub ahead of print]The humanised monoclonal antibody, Clazakizumab (CLZ), binds to circulating interleukin-6 (IL-6) cytokine rather than the IL-6 receptor, blocking both classical and trans-signalling. The purpose of this phase 2B study was to evaluate the efficacy and safety of clazakizumab in patients with inadequate response to methotrexate (MTX). Data on selected response rates – ACR20/50/70, DAS28-CRP, SDAI ≤3.3, CDAI ≤2.8 and the ACR/EULAR Boolean definition – and adverse events were collected from 418 patients. Findings from this study show all doses of clazakizumab, with or without MTX, were associated with rapid and significant improvement in disease activity. Clazakizumab was well tolerated showing safety results consistent with the known pharmacology of IL-6 blockade.