Early Prognostic Factors Associated with the Efficacy of Infliximab Treatment for Patients with Rheumatoid Arthritis with Inadequate Response to Methotrexate

INTRODUCTION Early prognostic factors for the clinical response in patients with rheumatoid arthritis (RA) after 1 year of treatment with infliximab (IFX) as part of routine clinical practice were investigated. METHODS Thirty-five patients with RA with an inadequate response to methotrexate were enrolled and administered IFX (3-9 mg/kg, every 4-8 weeks). Serum trough levels of IFX and levels of 9 cytokines were measured at baseline and at 3, 6 months, and 1 year. Associations between these parameters and clinical indicators were statistically analyzed. RESULTS Serum trough levels of IFX and serum levels of interleukin (IL)-6 in the early phase of IFX treatment were investigated. Patients with low serum IL-6 achieved a higher clinical response as evaluated by the European League Against Rheumatism response criteria. Notably, the serum levels of IL-6 and IL-10 at baseline exhibited a significant positive correlation with disease activity at 1 year. Low serum levels of IL-6 and IL-10 at baseline were associated with low Disease Activity Score 28 erythrocyte sedimentation rate (DAS28-ESR). Cut-off values of IL-6 (5.45 pg/mL) and IL-10 and (1.68 pg/mL) enabled discrimination of DAS28-ESR remission from non-remission with high sensitivity and moderate specificity. CONCLUSION Following the initiation of IFX treatment, early disease activity and remission were associated with serum levels of IL-6. Serum levels of IL-6 and IL-10 at baseline predict the efficacy after 1 year of treatment with IFX. Patients with high serum levels of IL-6 and IL-10 at baseline before IFX treatment might require more intensive therapy to achieve higher rates of clinical remission at 1 year. FUNDING Eisai Co., Ltd.