A biosimilar product needs to demonstrate biosimilarity to the originator reference product, and the quality profile of the latter should be monitored throughout the period of the biosimilar's development to match the quality attributes of the 2 products that relate to efficacy and safety. For the development of a biosimilar version of trastuzumab, the reference product, Herceptin®, was extensively characterized for the main physicochemical and biologic properties by standard or state-of-the-art analytical methods, using multiple lots expiring between March 2015 and December 2019. For lots with expiry dates up to July 2018, a high degree of consistency was observed for all the tested properties. However, among the lots expiring in August 2018 or later, a downward drift was observed in %afucose (G0+G1+G2). Furthermore, the upward drift of %high mannose (M5+M6) was observed in the lots with expiry dates from June 2019 to December 2019. As a result, the combination of %afucose and %high mannose showed 2 marked drifts in the lots with expiry dates from August 2018 to December 2019, which was supported by the similar trend of biologic data, such as FcγRIIIa binding and antibody-dependent cell-mediated cytotoxicity (ADCC) activity. Considering that ADCC is one of the clinically relevant mechanisms of action for trastuzumab, the levels of %afucose and %high mannose should be tightly monitored as critical quality attributes for biosimilar development of trastuzumab.

Background SB3 has been developed as a trastuzumab biosimilar, a therapeutic monoclonal antibody targeted to human epidermal growth factor receptor 2 (HER2), and approved by the European Commission and United States (US) Food and Drug Administration (FDA). During the developmental period of a biosimilar, setting an appropriate quality target is critical for assessing the similarity of the biosimilar product to the reference product. A stepwise approach should be taken to assessing similarity, beginning with extensive characterization of the reference product to establish the quality target. Objective In this study, we evaluated the similarity of SB3 to the reference product and the impact of changes in the biological profile of the reference product on similarity assessment. Methods Analytical similarity was assessed with defined test procedures in terms of critical quality attributes (CQAs) that could affect efficacy, potency, and safety, as well as for the non-CQAs that are related to process consistency. The quality target was established using up to 154 lots of European Union (EU)- and US-sourced Herceptin ® (reference product), analyzed during the developmental period of SB3. Results Trends of the EU- and US-sourced reference product showed that the biological profile exhibited two marked changes for Fc-related attributes, and then recovered to pre-change quality level. Since the similarity range set by pre-change lots was considered most relevant, the changed lots were excluded from establishing the similarity range, which resulted in tightened acceptance criteria. As shown in the results of similarity assessment using the stringent quality target ranges, SB3 exhibits highly similar functional activities compared to the reference product in terms of both CQAs and non-CQAs. Conclusion SB3 has been developed as a trastuzumab biosimilar approved in the EU and USA, and its manufacturing process is deemed to be robust and well-controlled within stringent quality target ranges.