Comparing tocilizumab biosimilar BAT1806/BIIB800 with reference tocilizumab in patients with moderate-to-severe rheumatoid arthritis with an inadequate response to methotrexate: a phase 3, randomised, multicentre, double-blind, active-controlled clinical trial

Background Biosimilars provide an opportunity to address unmet medical need by expanding access to biological treatments. This study aimed to show equivalent efficacy, and comparable safety, immunogenicity, and pharmacokinetic profiles of a proposed tocilizumab biosimilar BAT1806/BIIB800, to reference tocilizumab, in participants with rheumatoid arthritis with an inadequate response to methotrexate. Methods This phase 3, multicentre, randomised, double-blind, active-controlled, equivalence study comprised a 24-week initial treatment period (results reported here) and a 24-week secondary treatment period. Participants were recruited at 54 centres across five countries (China, Ukraine, Poland, Georgia, and Bulgaria). Patients with active rheumatoid arthritis with an inadequate response to methotrexate were randomly assigned (1:1:2) to receive reference tocilizumab up to week 48, or reference tocilizumab up to week 24 followed by BAT1806/BIIB800 up to week 48 (the two reference tocilizumab groups were analysed as a single group in this analysis), or BAT1806/BIIB800 up to week 48 (the BAT1806/BIIB800 group), administered by intravenous infusion once every 4 weeks at a starting dose of 8 mg/kg. The primary endpoint was the proportion of participants who had a 20% improvement in American College of Rheumatology criteria (ACR20) at week 12 (for the European Medicines Agency [EMA]) or week 24 (for the US Food and Drug Administration [FDA] and China National Medical Products Administration [NMPA]) using prespecified equivalence margins (95% CI –14·5 to +14·5 [EMA], 90% CI –12·0 to +15·0 [FDA], and 95% CI –13·6 to +13·6 [NMPA]). The International Council for Harmonisation E9(R1) estimand framework, with strategies for addressing intercurrent events, was implemented for the efficacy evaluations with expected differences as per the predefined equivalence margins. This trial is registered at ClinicalTrials.gov (NCT03830203) and EudraCT (2018-002202-31), and is closed to new participants. Findings Between Dec 19, 2018, and Jan 5, 2021, we randomly assigned 621 participants: 309 to the reference tocilizumab group and 312 to the BAT1806/BIIB800 group. The mean age was 50·5 years (SD 12·0), 534 (86%) were women, 87 (14%) were men, and 368 (59%) were White. For the primary estimands, estimated ACR20 response rates were 64·8% in the reference tocilizumab group and 69·0% in the BAT1806/BIIB800 group (treatment difference 4·1% [95% CI –3·6 to 11·9]) at week 12, and 67·9% in the reference tocilizumab group and 69·9% in the BAT1806/BIIB800 group (treatment difference 1·9% [90% CI –4·0 to 7·9; 95% CI –5·2 to 9·1]) at week 24. All confidence intervals were contained within the predefined equivalence margins. Comparable pharmacokinetic and immunogenicity profiles were observed for the reference tocilizumab and BAT1806/BIIB800 groups. Adverse events were reported by 201 (65%) participants in the reference tocilizumab group and 206 (66%) in the BAT1806/BIIB800 group; 196 (63%) participants in the reference tocilizumab group and 201 (64%) participants in the BAT1806/BIIB800 group reported a treatment-emergent adverse event. Five participants had a fatal event (reference tocilizumab n=1; BAT1806/BIIB800 n=4). Interpretation BAT1806/BIIB800 showed equivalent efficacy, and comparable safety, immunogenicity, and pharmacokinetic profiles as reference tocilizumab. Funding Bio-Thera Solutions and Biogen.