Sirukumab is a human monoclonal antibody targeting interleukin-6 (IL-6), a pro-inflammatory cytokine. It binds to soluble IL-6 with high affinity, preventing its interaction with both soluble and membrane-bound IL-6 receptors. It was investigated for the treatment of rheumatoid arthritis (RA), but development was discontinued after regulatory reviews highlighted safety concerns, including increased risk of serious infections and mortality.