Keystone EC, Wang MM, Layton M, et al. Clinical evaluation of the efficacy of the P2X₇ purinergic receptor antagonist AZD9056 on the signs and symptoms of rheumatoid arthritis in patients with active disease despite treatment with methotrexate or sulphasalazine. Ann Rheum Dis 2010;69:1630–5. This was published in the print issue with the incorrect doi 10.1136/ annrheumdis-2011-143578. The correct doi is 10.1136/ard.2010.143578 because this is the doi it was originally published with online first.