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Title: Understanding the impact of bioprocess conditions on monoclonal antibody glycosylation in mammalian cell cultures through experimental and computational analyses
Author: Sou, Si Nga
ISNI:       0000 0004 7228 4209
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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With positive outcomes from medical treatments, monoclonal antibodies (mAbs) are to date the best-selling biologics in the pharmaceutical market. The fact that a lot of blockbuster drugs are facing the period of patent cliffs and patents of many of them are due to expire in the next 5 years, places an urgency for better, cheaper and more efficient bioproduction processes, as well as the development of novel drugs and biosimilars. To address to this issue, application of the Quality by Design paradigm that was introduced by the Food and Drug Administration (FDA) is of paramount importance. Medical values and safety of monoclonal antibodies have been reported to rely on the carbohydrate structures that are attached to the mAb N-linked glycosylation site on each constant region. Fc-N-linked glycosylation is considered as a critical quality attribute (CQA) of these therapeutic proteins under the scope of Quality by Design. It was also reported that different bioprocess conditions during recombinant mAb production directly impact glycan compositions and their distribution on the molecules, although the mechanism behind this change is not fully understood. This lack of understanding limits process design and optimisation. To address this issue we examined the effect of mild hypothermia (32oC) and the different recombinant expression systems on mAb N-linked glycosylation, using experiments, flux balance analysis (FBA) and mechanistic modelling to identify resulting differences in cell metabolism. A defined mathematical model that mechanistically and quantitatively describes CHO cell behaviour and metabolism, mAb synthesis and its N-linked glycosylation profiles before and after the induction of mild hypothermia in SGE and TGE expression systems was also constructed, which we believe is the first quantitative model that relates mild hypothermia and TGE system to the four elements mentioned above. Not only does the model aid understanding of the way bioprocess conditions affect product quality, it also provides a platform for bioprocess design, control and optimisation in industry and helps the implementation of the Quality by Design principles. Results obtained from our computational studies suggested glycosyltransferases to be the key players for changes observed among different bioprocess conditions, based on results obtained from this thesis we then manipulated the expression of galactosyltransferase in particular, through a proof-of-concept experiment using miRNAs.
Supervisor: Kontoravdi, Cleo ; Polizzi, Karen M. Sponsor: Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral