4.12 Clinical similarity

Understanding biosimilarity

Table 4.5 Representative Functional Assay Types of mAbs

Antibody Target Assay

Infliximab Inhibition of TNF-alpha signaling Proliferation assay Adalimumab Inhibition of TNF-alpha signaling Proliferation assay Rituximab CD20 Binding assay (cytometry), ADCC assay, CDC assay Bevacizumab Vascular endothelial growth factor CDC assay Trastuzumab HER2, ErbB2 Proliferation assay, ADCC assay Cetuximab Epidermal growth factor receptor Proliferation assay Natalizumab Alpha4-integrin Binding assay (cytometry)

In a stepwise approach, once the structure of the product is established to be at least highly similar, its evaluation begins for the potency of the product. Matching the reference product pro les is done with a greater emphasis on matching all biological functions that include biological and functional activities, receptor binding, and immunochemical properties. Common tests used to demonstrate these include potency assay, effector functions (ADCC/CDC), Fc receptor family–binding activities, antigen binding, FcRN, and other MOAs. The test methods must be sensitive and resolving, and their importance well understood; for example, if ADCC is not matching, then optimization is required. However, all assays reported here have limitations that should also be understood, and it is for this reason that the regulatory agencies require orthogonal testing to con rm similarity. In the recent approval of a biosimilar product for lgrastim, a cell proliferation assay using murine myelogenous leukemia cells (NFS-60 cell line) was used to evaluate the biological product. This cell line carries the GCSF receptor, and it is commonly used to assess the biological activity of this growth factor. The bioactivity data were reported as a percentage relative to the applicant’s in-house reference standard calibrated against an international GCSF reference standard. These data were subjected to statistical analysis using equivalence testing where 2xSD (two times standard deviation) of the reference product was taken as the equivalence range.

There are three types of clinical studies conducted to establish biosimilarity: • The clinical pharmacology study to measure PK and, where available, PD parameters; there is no waiver of these trials. • The clinical response (meaning effectiveness and safety) in patients when no suitable PD model exists or where an appropriate animal model is not available to study the safety of the product; the FDA has made it abundantly clear that it is the

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