The aim of this exploratory analysis was to identify immunoglobin G (IgG) autoantibodies associated with early treatment response to methotrexate or to tocilizumab (i. e. interleukin-6 [IL-6] receptor inhibitor), each initiated as a first-line disease-modifying anti-rheumatic drug (DMARD) in the U-Act-Early study, in baseline serum samples from patients with early RA. Here, IL6 is linked to rheumatoid arthritis.