Background/Purpose: BAT1806 (also referred to as BIIB800) is a proposed biosimilar to tocilizumab reference product (TCZ). Results of this Phase 3, randomized, double-blind, active-controlled trial demonstrated that BAT1806 has equivalent efficacy and comparable safety, immunogenicity, and pharmacokinetic (PK) profiles as TCZ up to Week 24 (treatment period 1).¹ Here, the results from Weeks 24 to 48 (treatment period 2 [TP2]) are reported.

Methods: The study was conducted in 55 sites in China and Central Europe. Subjects with a diagnosis of RA according to the ACR/EULAR 2010 revised classification for at least 6 months prior to screening and who met the protocol-specified inclusion/exclusion criteria were randomized in a 2:1:1 ratio to one of three treatment groups: (1) BAT1806 up to Week 48, (2) TCZ up to Week 48, or (3) TCZ up to Week 24 followed by BAT1806 from Week 24 to Week 48, administered intravenously every 4 weeks at a dose of 8 mg/kg. Efficacy in terms of ACR20/50/70 response probabilities and DAS28-ESR and DAS28-CRP, PK, safety, and immunogenicity were assessed up to Week 48.

Results: Of 621 randomized subjects, the numbers of subjects continuing into TP2 were 290 (92.9%), 142 (92.2%), and 145 (93.5%) in groups 1, 2, and 3, respectively. Baseline characteristics were similar across groups at Week 24. At Week 48, ACR20 responders as proportions of evaluable subjects were: 253/280 (90.4%), 121/134 (90.3%), and 122/139 (87.8%) for groups 1, 2, and 3, respectively. ACR20/50/70 responses (Figure 1) and mean change in DAS28-ESR and DAS28-CRP (Figure 2) from baseline were comparable across groups. The proportions of subjects with serious treatment-emergent adverse events (TEAEs) in TP2 were similar between the treatment groups (Table 1). No deaths were reported during TP2. Eight subjects in group 1 reported 9 serious TEAEs, 2 of which (pneumonia and salpingo-oophoritis) were possibly treatment related. Five subjects in group 2 reported 5 serious TEAEs, 1 of which was possibly treatment related (laryngitis). Four subjects in group 3 reported 5 serious TEAEs, 1 of which was possibly treatment related (pneumonia). Anti-drug antibodies were reported at least once in 21.0%, 16.2%, and 18.6% of subjects in treatment groups 1, 2, and 3, respectively; of these subjects, all but 1 in the TCZ group tested positive for neutralizing antibodies (Table 1). Geometric mean (CV%) trough serum concentrations (µg/mL) were comparable for the 3 treatment groups: 13.1 (126.5), 12.7 (157.0), 12.4 (180.7) at Week 28 and 12.3 (82.7), 13.4 (89.2), 13.5 (130.6) at Week 44 for groups 1, 2, and 3, respectively. The study was conducted between 2019–2020 during the COVID-19 pandemic. Post-hoc exploratory analyses indicated that the pandemic had limited impact, which was similar between the treatment groups (data not shown).

Conclusion: Efficacy, safety, immunogenicity, and PK profiles were comparable between BAT1806, TCZ/BAT1806, and TCZ throughout TP2. No safety or clinically relevant immunogenicity issues were observed in subjects switched from TCZ to BAT1806

Reference
1. Leng X, et al. Ann Rheum Dis. 2022;81(suppl. 1):388.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/fifty-two-week-results-from-a-phase-3-randomized-double-blind-active-controlled-clinical-trial-to-compare-bat1806-biib800-a-proposed-tocilizumab-biosimilar-with-a-tocilizumab-reference-product-in/