Background: Trastuzumab is a blockbuster monoclonal antibody that has revolutionized the treatment of HER2-positive breast and gastric cancers. With the increasing availability of biosimilar monoclonal antibodies in clinical practice, independent verification of biosimilarity using products sampled from a real-world supply chain is important to assure clinicians and the patients to use these products confidently. Objective: The aim of this study is to assess the biosimilarity of AryoTrust, a trastuzumab biosimilar, in comparison with the reference product Herceptin. AryoTrust and Herceptin products were randomly withdrawn from Iraqi hospitals to reflect medicines administered in real clinical settings. Methods: AryoTrust and Herceptin were compared using an extensive set of orthogonal analytical techniques which included SDS-PAGE, ion-exchange chromatography, capillary isoelectric focusing, peptide mapping, N-glycan profiling, circular dichroism, differential scanning calorimetry, and surface plasmon resonance. In addition to these teste, functional comparability was also tested using an HER2-dependent cell-based proliferation inhibition bioassay. Results: The results showed that both products have highly comparable profiles in all assessed attributes. The analysis showed similar molecular integrity and purity, identical primary structure, comparable charge heterogeneity, similar isoelectric points (pI) of the main isoform, close glycosylation patterns (mainly, by core-fucosylated complex-type glycans), similar higher-order structural features, and thermal stability. The receptor binding studies exhibited comparable binding affinities with Fcγ receptors and FcRn. Finally, the cell-based bioassay revealed comparable dose–response curves with similar EC50 values and relative potency. Conclusions: The integrated analytical and functional data support the biosimilarity of AryoTrust to the reference product Herceptin, which has been marketed and used in Iraq. This study provides real-world scientific evidence supporting confidence in the quality and comparability of this trastuzumab biosimilar and reduces any doubt in the product and at the same time emphasizes the value of independent post-marketing biosimilarity assessments.
