Post-switch Effectiveness of Etanercept Biosimilar Versus Continued Etanercept in Rheumatoid Arthritis Patients with Stable Disease: A Prospective Multinational Observational Study

Introduction To better inform clinicians about the use of etanercept biosimilar (SB4) in patients with rheumatoid arthritis (RA), COMPANION-B, a prospective real-world observational study, evaluated the effectiveness of the voluntary switch from originator (etanercept, ETN) to SB4 in patients with stable RA (low-disease activity/remission). Methods The study recruited adult patients (18 years or older) with RA (2010 American College of Rheumatology criteria) prescribed ETN as their first or second biologic for at least 6 months across 14 sites in Canada and five in Australia. Patients had stable disease (Disease Activity Score-28 using erythrocyte sedimentation rate [DAS28-ESR] less than 3.2) at enrollment with no evidence of flare within the previous 3 months. Concomitant disease-modifying antirheumatic drugs (DMARDs) were permitted. Patients could elect to continue ETN or voluntarily switch to SB4 in consultation with their doctors. The primary effectiveness measure was the proportion of patients with disease worsening (defined as a DAS28-ESR increase of at least 1.2 from baseline and minimum score of at least 3.2 or a defined modification in RA treatment) during 12 months of follow-up. The secondary effectiveness measure was the proportion of patients with disease worsening at month 6. Serious adverse events (SAEs) and non-serious adverse reactions (NSARs) were recorded. Results Of 163 patients enrolled, 109 elected to continue on ETN and 54 switched to SB4; 65.8% of patients received non-biologic DMARD(s), 52.6% methotrexate, and 10.5% oral corticosteroid(s). At month 12, the proportion of patients with disease worsening was comparable in the ETN group (22.8% [95% CI 15.0-32.2]) and SB4 group (17.6% [95% CI 8.4-30.9]). Similarly, the proportions of patients with disease worsening were also comparable at month 6 (ETN: 7.9% [95% CI 3.5-15.0]; SB4: 7.8% [95% CI 2.2-18.9]). SAEs were low and similar across both groups (ETN: 8.7%; SB4: 5.7%). NSARs were slightly higher in the SB4 vs. ETN group (13.2% vs. 2.9%). Conclusions SB4 demonstrated comparable effectiveness to ETN over 12 months in patients with stable RA who voluntarily switched to the biosimilar in a real-world setting.