Abstract

In this work a rituximab follow-on biologic, Zytux is tested for its biosimilarity to the reference originator product, MabThera. The test involved an analytical assessment exercise done head-to-head on samples of Zytux and MabThera withdrawn randomly from the Iraqi governmental hospitals. This analytical assessment encompassed methods for comparing the quality aspects of the product such as protein (rituximab) content, purity, integrity, primary structure, charge variants, higher-order structure, and in vitro biological activity. Rituximab concentration and pH of Zytux and MabThera were comparable and lay within the product specification. Both products showed comparable integrity and purity profiles when tested by SDS-PAGE analysis. Rituximab from both products showed a similar primary structure profile using HPLC-based peptide mapping. The results also showed comparable charge variant profiles obtained by cation exchange chromatography analysis, comparable secondary and tertiary structures probed by circular dichroism (CD) scan and CD-melt, respectively, and finally comparable biological activity of both products using complement-dependent cytotoxicity (CDC) assay. Overall results obtained in this study suggest a high degree of similarity. Therefore, Based on these studies one can conclude that Zytux is a likely biosimilar to MabThera, even though more studies are needed as part of the “totality of evidence” required to ensure the biosimilarity of rituximab follow-on biologic to the reference product‎.

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