S25: The interaction of host cell protein dynamics with process variables during the recovery of monoclonal antibodies

The production of monoclonal antibodies (MAbs) in mammalian cell culture has now become well established enabling expression of 5 g.L^-1 or more to become commonplace. These increased titres directly improve the economics in the upstream process, shifting a greater proportion of the production costs to downstream processing.  Such changes in the upstream process can also place differing challenges on the performance of downstream operations in a typical platform process. A key class of contaminants these operations are designed to remove are host cell proteins (HCPs) as they can produce an immunogenic response in patients.

In this study we have chosen to characterise the critical HCP components in terms of their persistence in a platform for MAb production. This is performed using 2D-polyacryamide gel electrophoresis and mass spectrometry analysis. Fed-batch cell culture and scale-down processing methodologies provide the basis to investigate the impact of both up and downstream process variables. This integrated approach is applied to null and producer cell lines. In one example we identify a number of intracellular proteins (e.g. protein disulphide isomerise; elongation factor 2; calreticulin) that exhibit a significant change in abundance with progression of culture relative to the general increase in HCP concentration.

Such characterisation is important for an understanding of process consistency and robustness, as the subsequent downstream process must be able to cope with such changes in relative abundance. Ultimately the information may enable a more directed approach to the development of purification strategies.