BACKGROUND: BAT1806/BIIB800 (Tofidence™/tocilizumab-bavi), a biosimilar of tocilizumab, demonstrated a high degree of analytical and functional similarity to reference tocilizumab (TCZ) in a comprehensive comparative analytical assessment. Minor differences with respect to TCZ were observed for some attributes and this study assessed the potential impact of these differences through structure activity relationship characterization. METHODS: Structure activity relationship studies were conducted to assess glycation, glycosylation, charge variants, hydrophobicity, oxidation, and deamidation differences, using a range of investigative techniques. Structure activity relationship studies were performed on one lot each of BAT1806/BIIB800 and TCZ (European Union sourced only) except for glycation, where additional lots sourced from China and the USA were used. RESULTS: Average total glycated protein content of BAT1806/BIIB800 was higher than TCZ (10.08% vs 1.19%)
however, biological activity, including target binding and functional potency, was unaffected. Stress-induced glycation of BAT1806/BIIB800 and TCZ also did not affect the biological activity of the products despite up to 60% total glycation content. Minor differences were observed between BAT1806/BIIB800 and TCZ in glycosylation, charge variants, hydrophobicity, oxidation, and deamidation without a relevant impact on interleukin-6 receptor binding, Fc-receptor binding, and effector functions. In forced degradation studies, oxidation and deamidation trends were comparable between the two products. CONCLUSIONS: Comparative structure activity relationship characterization of BAT1806/BIIB800 and TCZ indicated that there are no relevant differences in quality attributes between BAT1806/BIIB800 and reference TCZ. Observed differences between BAT1806/BIIB800 and TCZ had no functional impact on BAT1806/BIIB800. The results support the conclusion that BAT1806/BIIB800 is similar to TCZ.