As products of living cells, biologics are far more complicated than small molecular-weight drugs not only with respect to size and structural complexity but also their sensitivity to manufacturing processes and post-translational changes. Most of the information on the manufacturing process of biotherapeutics is proprietary and hence not fully accessible to the public. This information gap represents a key challenge for biosimilar developers and plays a key role in explaining the differences in regulatory pathways required to demonstrate biosimilarity versus those required to ensure that a change in manufacturing process did not have implications on safety and efficacy. Manufacturing process changes are frequently needed for a variety of reasons including response to regulatory requirements, up scaling production, change in facility, change in raw materials, improving control of quality (consistency) or optimising production efficiency. The scope of the change is usually a key indicator of the scale of analysis required to evaluate the quality. In most cases, where the scope of the process change is limited, only quality and analytical studies should be sufficient while comparative clinical studies can be required in case of major changes (e.g., cell line changes). Biosimilarity exercises have been addressed differently by regulators on the understanding that biosimilar developers start with fundamental differences being a new cell line and also a knowledge gap of the innovator's processes, including culture media, purification processes, and potentially different formulations, and are thus required to ensure that differences from innovators do not result in differences in efficacy and safety.
Keywords: biologics; biosimilarity; biosimilars; comparability.