Virus reduction terminal inactivation steps

Plasma-derived therapeutic proteins are parenteral biologies that are purified on an industrial scale. All biologies derived from human sources, such as plasma, carry the risk of viral contamination. Thus, in order to market a medicinal product derived from human plasma, manufacturers must assure the absence of specific viral contamination. Virus validation studies are performed to evaluate the capacity of a manufacturing process to remove viral contaminants. Virus clearance across three different terminal inactivation steps, low pH incubation of immunoglobulins (IgG), pasteurization of albumin, and freeze dry/dry heat treatment of plasma-derived products (Factor VIII and Protein G), is discussed in this article. The data show that, like all other upstream virus reduction steps, the methods used for terminal inactivation are process and product dependent, and that the reduction factors for an individual step may be overestimated or underestimated due to inherent limitations or inadequate designs of viral validation studies. 

Screening and selection of the source plasma will only avoid contamination by known pathogens. The protein purification steps and specific virus reduction methods used in production processes, however, will inactivate and/or remove both known and unknown viruses. Terminal virus inactivation treatments are applied to product in final container and must balance virus inactivation with any modifications to protein immunogenicity, activity, and yield. While many upstream virus inactivation steps rely on chemical methods that involve the addition and subsequent removal of toxic agents (e.g., solvent/detergent), physical methods for virus inactivation, such as pH and heat, are used for terminal steps. 

Manufacturing processes have evolved dramatically over the last few years. In the late 1980s, 76 /o of hemophiliacs were HCV positive, ° and between 1979 and 1985, approximately 50 /o of hemophiliacs had acquired HIV from plasma-derived FVIII. Since then, however, most U.S.-licensed plasma derivatives have not transmitted HBV, HCV, or HIV as a result of improvements in donor screening and test methods, and the inclusion of effective upstream virus-reduction and terminal virus-inactivation steps in manufacturing processes. Residual risks of virus transmission from plasma-derived products are now largely associated with non-enveloped viruses. " Thus, the need for additional terminal or upstream virus inactivation/removal steps still exists, but the current challenge is to develop cost effective methods against physico-chemically resistant non-enveloped viruses, such as human parvovirus B19. 

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