Forced Degradation Studies to Identify Critical Process Parameters for the Purification of Infectious Measles Virus

Oncolytic measles virus (MV) is a promising treatment for cancer but titers of up to 10¹¹ infectious particles per dose are needed for therapeutic efficacy, which requires an efficient, robust, and scalable production process. MV is highly sensitive to process conditions, and a substantial fraction of the virus is lost during current purification processes. We therefore conducted forced degradation studies under thermal, pH, chemical, and mechanical stress to determine critical process parameters. We found that MV remained stable following up to five freeze-thaw cycles, but was inactivated during short-term incubation (< 2 h) at temperatures exceeding 35 °C. The infectivity of MV declined at pH < 7, but was not influenced by different buffer systems or the ionic strength/osmolality, except high concentrations of CaCl₂ and MgSO₄. We observed low shear sensitivity (dependent on the flow rate) caused by the use of a peristaltic pump. For tangential flow filtration, the highest recovery of MV was at a shear rate of ~5700 s^-1. Our results confirm that the application of forced degradation studies is important to identify critical process parameters for MV purification. This will be helpful during the early stages of process development, ensuring the recovery of high titers of active MV particles after purification.