Characterization for the Similarity Assessment between Proposed Biosimilar SB12 and Eculizumab Reference Product Using a State-of-the-Art Analytical Method

SB12 is being developed as a proposed biosimilar to eculizumab reference product (RP), a humanized monoclonal antibody (IgG2/4 kappa immunoglobulin) that binds to the human C5 complement protein. Binding to this protein inhibits complement-mediated intravascular hemolysis by blocking its cleavage into C5a and C5b. Eculizumab RP is indicated for the treatment of patients with paroxysmal nocturnal hemoglobinuria (PNH) to reduce hemolysis, atypical hemolytic uremic syndrome (aHUS) to inhibit complement-mediated thrombotic microangiopathy, generalized myasthenia gravis who are anti-acetylcholine receptor antibody-positive, and neuromyelitis optica spectrum disorder in adult patients who are anti-aquaporin-4 antibody-positive. The objective of this study was to demonstrate structural, physicochemical, and biological similarity between eculizumab RP and SB12 using various state-of-the-art analytical methods. Comprehensive analytical characterization was conducted with side-by-side comparison of SB12 with European Union (EU) and United States (US) eculizumab RPs using various analytical methods (more than 40 state-of-the-art assays). Comparisons included purity, product-related impurity, charge heterogeneity, primary structure, post-translational modification, higher-order structure, quantity, Fab-related biological activities (potency and binding activity), and Fc-related biological activities. Based on the analytical similarity assessment, the structural, physicochemical, and biological characterization results demonstrated that SB12 is highly similar to the EU and US eculizumab RP. In the structural aspects, it was confirmed that there is no difference between post-translational modification profiles and higher-order structures of SB12 compared with the eculizumab RP. Product-related impurities in the form of aggregates and charge variants were also confirmed to be similar. Mechanism of action (MoA)-related biological activities showed that SB12 is highly similar to the EU and US eculizumab RP with respect to overall critical and non-critical quality attributes analyzed. Moreover, similarity of comparative binding tendency of SB12 and eculizumab RP to Fc gamma receptors and C1q was confirmed through additional characterization methods. Based on these results, SB12 is expected to have highly similar safety and efficacy compared with eculizumab RP. In summary, the overall analytical characterization and similarity assessment results show that SB12 is highly similar to the EU and US eculizumab RP in terms of structural, physicochemical, biophysical, and biological attributes.