Interleukin (IL)-6 is a pleiotropic cytokine involved in the pathophysiology of rheumatoid arthritis (RA). Sirukumab is a human monoclonal antibody that binds to IL-6 with high affinity and specificity. This long-term extension (LTE) study of the SIRROUND-D and SIRROUND-T studies assessed long-term safety and efficacy of sirukumab in adults with moderate-to-severe RA refractory to conventional disease-modifying antirheumatic drug therapy or antitumor necrosis factor agents. Patients received sirukumab 100 mg subcutaneously (SC) every 2 weeks (q2w) or sirukumab 50 mg SC every 4 weeks (q4w). 1820 patients enrolled in the LTE; median exposure was 2.34 and 2.07 years in sirukumab 50 mg q4w and 100 mg q2w groups, respectively. Adverse events (AEs) occurred in similar proportions between groups, with the exception of major adverse cardiovascular events (MACE), which were more common in the 50 mg q4w versus 100 mg q2w group (2.2% vs 1.0%), and injection-site reactions, more common in the 100 mg q2w group versus 50 mg q4w group (7.5% vs 3.7%). The most common serious AEs were infections (10% of the patients); 32 (1.8%) patients died during the study (primarily from serious infection and MACE). Malignancies were reported in 24 (1.3%) patients. Gastrointestinal perforations, hepatobiliary abnormalities and changes in laboratory parameters were rare. Reductions in RA signs and symptoms and improvements in physical function were maintained throughout the LTE. The safety profile of sirukumab in the LTE remained consistent with that reported in SIRROUND-D and SIRROUND-T and efficacy was maintained. NCT01856309.