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.