Chemically defined media modifications to lower tryptophan oxidation of biopharmaceuticals.

Oxidation of biopharmaceuticals is a major product quality issue with potential impacts on activity and immunogenicity. At Eli Lilly and Company, high tryptophan oxidation was observed for two biopharmaceuticals in development produced in Chinese hamster ovary cells. A switch from historical hydrolysate-containing media to chemically defined media with a reformulated basal powder was thought to be responsible, so mitigation efforts focused on media modification.