Switching from originator infliximab to biosimilar infliximab in Japanese patients with rheumatoid arthritis achieving clinical remission (the IFX-SIRIUS study I): Study protocol for an interventional, multicenter, open-label, single-arm and noninferiority clinical trial with clinical, ultrasound, and biomarker assessments

BACKGROUND: The introduction of biological disease-modifying anti-rheumatic drugs (bDMARDs) into clinical practice has dramatically improve the clinical outcomes of individuals with rheumatoid arthritis (RA). However, bDMARDs are associated with high costs, which has resulted in restricted treatment access and a burden on medical insurance finances. Although biosimilars offer cost-saving, their effectiveness and safety must be established in Post-Marketing Surveillance (PMS). Infliximab (IFX), a chimeric monoclonal antibody to TNF-alpha, is the first bDMARD; its biosimilar, CT-P13, is the first biosimilar DMARD approved for RA treatment in Japan. We will evaluate whether switching from originator IFX to CT-P13 is not inferior for maintaining non-clinical relapse to continued treatment with originator IFX in RA patients achieving clinical remission. METHODS/DESIGN: This study is an interventional, multicenter, open-label, single-arm against historical control and noninferiority clinical trial with a 24-week follow-up. Eighty RA patients who are treated by originator IFX for ≥24 weeks and are achieving clinical remission will be included. Patients will be switched to CT-P13 with the unchanged dosing regimen. We will evaluate disease activity by measuring clinical disease activity indices and by using musculoskeletal ultrasound (MSUS). The primary endpoint is the ratio of patients who experience a nonclinical relapse during the study period. Important secondary endpoints are the changes from the baseline of the MSUS scores. We will also comprehensively analyze the serum levels of many biomarkers such as cytokines and chemokines. DISCUSSION: The study results are expected to show the noninferiority of switching to CT-P13 over the continuation of originator IFX. The strength of this study is its prospective evaluation of therapeutic efficacy using not only clinical disease activity indices but also MSUS to accurately and objectively evaluate disease activity at the joint level among patients drawn from multiple centers with a standardized evaluation by MSUS. We will explore whether parameters at baseline can predict a nonclinical relapse after switching from originator IFX to CT-P13 by integrating multilateral assessments, i.e., clinical disease activity indices, MSUS findings, and serum biomarkers. TRIAL REGISTRATION: This study was registered in the Japan Registry of Clinical Trials (https://jrct.niph.go.jp) on October 11, 2019 as jRCTs071190030.