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.

BackgroundSB3, a biosimilar of Herceptin® (trastuzumab, hereinafter referred to as reference product) is currently approved in the EU, Korea, Australia, the USA, and Brazil for the treatment of human epidermal growth factor receptor (HER) 2-positive early and metastatic breast cancer and HER2-positive metastatic gastric cancer. Previously, the biological similarity of SB3 to EU- or US-sourced reference product was assessed using various cell-based and binding assays.ObjectiveIn this paper, as a part of its similarity assessment, SB3 was evaluated for additional characteristics related to its molecular mechanism of action (MoA).MethodsFor extracellular effects of SB3, HER2-overexpressing cancer cell lines were used to assess expression of surface HER2, shedding of the extracellular domain of HER2, and antibody-dependent cell-mediated phagocytosis (ADCP) activity. For intracellular effects, Akt phosphorylation and vascular endothelial growth factor (VEGF) release were assessed. Additionally, in vitro docetaxel or pertuzumab combination experiments were performed for further characterization; anti-proliferation, HER2/HER3 dimerization inhibition, apoptosis, and antibody-dependent cell-mediated cytotoxicity (ADCC) assays were used.ResultsIt was confirmed that SB3 is highly similar to the reference products on quality attributes related to extracellular/intracellular efficacy. This similarity was also confirmed during combination studies with docetaxel and pertuzumab.ConclusionOverall, the equivalence of SB3 with reference product in MoA-related qualities in in vitro mono- and combination therapy experiments may support clinical bioequivalence of the two substances.

e14001 Background: The human epidermal growth factor receptor (HER) family plays a critical role in proliferation and survival of cancer cells. Trastuzumab is a recombinant humanized monoclonal antibody that blocks signaling pathways of HER2 tyrosine kinase receptor via binding to subdomain IV of HER2 extracellular domain. A subdomain II targeting therapeutic antibody (DII antibody, pertuzumab) binds to a different region on the same protein. A combination of the two different antibodies might provide a more effective antitumor activity without binding interference [1] . In this study, we evaluate in vitro antitumor activity of SB3 used in the same manner as Herceptin, in combination with a DII antibody that complements the mechanism of action of trastuzumab. [1] Nahta et al, [CANCER RESEARCH 64, 2343–2346, April 1, 2004]. Methods: Similarity assessment of in vitro antitumor activity between SB3 and Herceptin was performed on HER2-overexpressing breast and gastric cancer cells through analyzing HER2 dimerization, cell proliferation and survival activities, and antibody-dependent cellular cytotoxicity (ADCC) in the presence of a DII antibody. Combination index was calculated to evaluate the synergistic effect. Results: SB3 and Herceptin in combination with a DII antibody, showed similar in vitro inhibition rate for HER2/HER3 heterodimerization. The HER2-overexpressing breast and gastric cancer cells growth inhibition rate was similar whether SB3 or Herceptin was used in combination with a DII antibody. This effect was also shown in apoptosis activity by measuring caspase 3/7 expression. In terms of biological effect via Fc function, cell killing activity was assessed by ADCC assay in the presence of a DII antibody, and non-synergistic effect was shown with both SB3 and Herceptin. Conclusions: This study has concluded that SB3, as a trastuzumab biosimilar, demonstrates highly similar in vitro antitumor activity in experimental conditions when combined with a DII antibody, resulting in enhanced cell growth inhibition and apoptosis activities by inhibiting HER2 dimerization in HER2-positive cancer cells.