Background Biosimilar monoclonal antibodies (mAb) are expressed in unique host cell systems and without knowledge of specific process conditions, which are proprietary to the innovator. A biosimilar developer may choose to express a biosimilar mAb in a cell expression system of a similar lineage as the innovator, or one that is quite different. The choice of expression system can have an impact on many aspects of the molecule, including the N-linked glycosylation of the mAb, which may ultimately affect efficacy, safety or immunogenicity. Thus, multiple factors must be considered in choosing an appropriate expression system and process, with the ultimate goal of producing a mAb with highly similar analytical properties to the innovator mAb, and most importantly matching all functional aspects of the molecule, whether or not they are thought to be involved in the mechanisms of action.
Objectives The studies were designed to characterize analytical similarities and differences in mAbs produced in differing cellular expression systems, and to identify the optimal expression system for achieving functional similarity of two mAbs.
Methods Two case studies are presented, one examining the production of a proposed biosimilar mAb in a similar host expression system, and the other case examining production of a proposed biosimilar in a different host expression system. In the first case both mAbs are produced in cells of the CHO lineage, and in the second case a mAb produced in NS2/0 is compared to a mAb produced in CHO cells. The glycan profile of innovator and proposed biosimilar mAb are assessed, as well as resulting ADCC and CDC activity of the molecules.
Results Characterization of mAb1 demonstrates that two mAbs of the same amino acid sequence and expressed in the same parental expression system can result in differences in glycan distribution. These differences in glycans could not be resolved with process development, and had significant impact on functional activity of mAb1. In contrast, characterization of mAb2 illustrates the ability to match functional activity between an innovator mAb and proposed biosimilar, even with differences in choice of cellular expression system and the expected underlying differences in glycan distribution.
Conclusions Analytical differences, especially with respect to the N-linked glycan profile, should be expected between a biosimilar mAb and the innovator mAb, as well as between different biosimilar mAbs compared to each other. In a step-wise approach to biosimilar development, analytical differences between the proposed biosimilar mAb and the innovator should be carefully characterized, and functional similarity should be demonstrated, before proceeding with clinical studies.
Disclosure of Interest T. Born Shareholder of: AMGEN, Employee of: AMGEN, V. Fung Shareholder of: AMGEN, Employee of: AMGEN