Predication of Sialic Acid Reduction in CHO Culture

Sialic acid content is an important quality attribute in the development of many therapeutic glycoproteins. Increased sialic acid content is often linked to an increased half-life in the human body. In a GS-CHO cell line producing a recombinant enzyme, we observed that the total sialic acid content (TSAC) of the glycoprotein decreased over time. As the enzyme is being produced in a second generation process using a new cell line, it is important to determine the primary cause of this decline to help match product quality of the original process. A series of studies were performed to measure TSAC in standard culture conditions as well as in a cell-free harvest hold. In addition, sialidase activity was measured in daily samples, and compared to lactate dehydrogenase (LDH) levels. In a preliminary study, some samples were held at production temperature for 5 days. A sample removed on the fourth day of the culture did not change whereas a sample from the eighth day lost 34% of its TSAC. With this information, a mathematical model was established to estimate TSAC. The model could potentially be used to predict TSAC based on culture parameters including pH, temperature, and viability.