Improving monoclonal antibody production from Chinese hamster ovary cells

Abstract

Chinese Hamster Ovary (CHO) cells are used for the production of many therapeutic proteins, including the majority of monoclonal antibodies (mAbs). While significant progress has been made in improving mAb production using CHO cells, challenges remain in producing sufficient quantities of nextgeneration biologics, such as fusion proteins and bi-specific antibodies.

Additionally, production instability (i.e., loss of mAb productivity) during long term culture remains a significant problem. Stability studies, which take several months to complete, are a bottleneck in cell line development. A landing pad system for expression vector component comparison was integrated into a CHO host cell line. To demonstrate the functionality of the system, the strength of various constitutive promoters were tested by quantifying mCherry expression levels. This system will help facilitate the development of future expression vectors and enable systematic identification and optimisation of components to enhance CHO cell productivity.

A system which can predict the production stability of recombinant CHO cell lines, prior to the completion of a stability study, was envisaged. To pursue this, the production stabilities of 2 monoclonal CHO cell lines (32-124 and 32-121) producing the same mAb were characterised over ~60 generations. Loss of volumetric productivity during long term culture was observed in the 32-121 cell line whereas 32-124 exhibited a minimal decrease. Further analyses of growth characteristics, specific productivity, metabolite profiles, gene copy number, and transgene mRNA expression were subsequently conducted to investigate the underlying cause of productivity loss. The Berkley Lights Beacon® system was subsequently used to compare the two cell lines at generation 15. The results showed differences in both production and growth variability between the two cell populations, as well as an increased frequency of low-producing fast-growing cells in the 32-121 cell line. The method developed during this study will add to existing strategies for identifying early indicators of instability in CHO cell lines.