Efficacy and Safety of Switching from Innovator Rituximab to Biosimilar CT-P10 Compared with Continued Treatment with CT-P10: Results of a 56-Week Open-Label Study in Patients with Rheumatoid Arthritis

Background CT-P10 is a biosimilar candidate of innovator rituximab (RTX) that demonstrated a comparable clinical profile to RTX in a phase I randomized controlled trial (RCT) in rheumatoid arthritis (RA) (ClinicalTrials.gov identifier: NCT01534884). Objective This open-label extension (OLE) study (NCT01873443) compared the efficacy and safety of CT-P10 in patients with RA who received CT-P10 from the outset (i.e., from the start of the RCT and also in the OLE; 'maintenance group') with those who received RTX during the RCT and switched to CT-P10 during the OLE ('switch group'). Methods Patients who completed the RCT were recruited. Based on the Disease Activity Score using 28 joints (DAS28) and predefined safety criteria, patients could receive up to two courses of CT-P10 during the OLE. Efficacy [DAS28 and European League Against Rheumatism (EULAR) response], safety and immunogenicity were assessed. Results Eighty-seven patients were enrolled; 58 and 29 had previously received CT-P10 or RTX, respectively, in the RCT. Of these, 38 (65.5%) and 20 (69.0%) were treated with CT-P10 in the OLE and therefore comprised the maintenance and switch groups, respectively. The mean change in DAS28-erythrocyte sedimentation rate (ESR) from baseline (week 0 of RCT) at week 24 of the first OLE treatment course in the maintenance and switch groups was -2.7 and -2.4, respectively. The proportion of patients with good/moderate EULAR responses was also comparable between groups. Antidrug antibodies were detected in 13.2 and 15.0% of patients in the maintenance and switch groups, respectively, at week 24 of the first OLE course. CT-P10 treatment was well-tolerated when administered for up to 2 years or after switching from RTX. Conclusion In this study population, comparable efficacy and safety profiles were observed in patients who switched from RTX to CT-P10 and those maintained on CT-P10 throughout treatment.