Using Sensitivity Analysis to Simplify the Virus Safety Factor Calculation in the Manufacture of Biopharmaceuticals

Virus safety of biopharmaceuticals produced in cells of animal origin is governed by regulatory guidelines. It is ensured through raw material controls, cell substrate testing, and evaluation of the purification process for virus clearance capability. An additional control for cell lines that contain endogenous viruses is the virus safety factor (VSF) calculation, to demonstrate that the virus clearance exceeds the amount of potential endogenous virus in a dose of product. Product-specific input data (product titer, process yield, intended dose, purification process virus clearance capability, and the measured titer of endogenous virus produced by the cells) are typically used for the calculation. A wide range of relevant data was obtained from the production of monoclonal antibodies in Chinese Hamster Ovary (CHO) cells, and a sensitivity analysis was performed by using Monte Carlo simulations to determine which input data had the most significant impact on the range and distribution of the VSF. The sensitivity analysis suggested that the VSF calculation can be streamlined to include virus clearance capability, the endogenous virus titer, and dose while excluding product titer and process yield. Furthermore, the simulated VSF exceeded 4 log₁₀ in 96% of the simulations, providing a high level of assurance of virus safety for antibodies produced in CHO cells and purified within specified operational parameters.