(27c) Base Media and Feed Optimization for Non-Antibody Proteins
Production processes for antibody-based therapeutics have been well described and often involve fed-batch culture. Many non-antibody biotherapeutics are now either already approved or in development including recombinant forms of Erythropoietin (EPO), Tissue Plasminogen Activator (tPA), coagulation proteins (eg, Factor IX) and enzymes used for treatment of lysosomal storage diseases (eg, beta glucosidase, alpha galactosidase). The diversity of non-antibody proteins, including differences in primary/secondary structure, level of post-translational modification, stability and potential for toxicity can create problems for the process engineer. For example, additives to the medium, like a specific cofactor may be required to enable expression of the active form of the protein. Solubility, stability and availability of the cofactor or other additive in an animal-origin-free (AOF) form may be problematic. Some proteins may either be unstable once secreted into a protein-free culture medium or toxic to the cells. Such proteins may require a perfusion-based process, which is difficult to model in small scale. Many non-antibody proteins are heavily glycosylated and thus are susceptible to the actions of glycosidases released from dying cells, and to media or process conditions favoring ammonium accumulation. Earlier harvests, controlled feeds and non-ammoniagenic media components have been shown to improve glycoform structures in some systems. This presentation will discuss both general and specific media and feed development issues for non-antibody proteins, including component and process modifications that can impact protein titer, quality and stability.