Discoloration source and control of a biotechnological drug product manufactured using a high titer production...

Control of product quality attributes is central to the development of a safe and efficacious therapeutic protein product. The product color, as a potential critical quality attribute, can be a good indicator of protein structural integrity, quality of formulation excipients, levels of process impurities and/or existence of potential contaminants. In this study a range of product colors including an out of specification (OOS) brownish color from visual inspection were observed during the development of a monoclonal antibody (mAb) therapeutic protein using a high titer production process. Following systematic in-depth studies supported with various analytical characterization techniques, the original source of the observed discoloration (i.e., color change from colorless or slightly yellow to a brownish color) is attributed to cyanocobalamin, a critical nutrient component used in the cell cultural media. Comparing to the conventional manufacturing process where no color issues were observed, discoloration found in current study was most likely attributed to the intensified cell culture process used in high titer production, where higher concentrations of cyanocobalamin were employed and higher viable cell densities were produced, both of which created a favorable condition promoting the generation of elevated levels of reactive cobalamin and its enhanced binding to the mAb. Although no safety concerns or product impact is expected, the residual cobalamin as a process impurity must be properly controlled to a consistent and acceptable level via a product release specification. A specification method was thus developed and validated in this study providing a simple yet robust measurement of total cobalamin in the product using its constituent elemental cobalt as a surrogate with an analytical procedure based on inductively coupled plasma mass spectrometry (ICP-MS). The current study highlights the complexity and potential challenges in the development of a high titer production process, where increased concentrations of cell culture components in the production bioreactor can result in unexpected component interactions, presenting potential risks to product quality. The comprehensive approach described in this study presents a systemic means for root cause analysis of an OOS result and also a sound strategy for developing controls for product quality attributes such as process impurities.