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Development of Protein-Like Reference Material for Semi-Quantitatively Monitoring Visible Proteinaceous Particles in Biotherapeutics



Srivalli Telikepalli, Kristen Gonzalez, Sonia Dragulin-Otto, Dean C. Ripple, Michael J. Carrier, M Khan


Visual inspection of biotherapeutics is required at various stages of drug production and manufacturing to ensure quality and consistency of drug products. Inherent particles, composed of aggregated protein from the drug-product, may potentially pose safety and efficacy concerns when administered to the patients; therefore, it is crucial to monitor and characterize the particles for safety and efficacy. However, even if trended and tracked for quality control, such particles may be acceptable on a case-by-case basis and become a critical quality attribute of the protein product. Monitoring these visible inherent proteinaceous particles poses numerous challenges in the industry due to differing interpretations of guidelines and due to a lack of a universal protein-like particle standard. The aim of this work is to reduce some of these challenges by evaluating abraded ethylene tetrafluoroethylene (ETFE) as a visible protein-like particle surrogate and by illustrating a semi-quantitative method to monitor inherent proteinaceous particles in biotherapeutics during the drug development process. Chemically inert ETFE particles, with irregular morphology, and a refractive index similar to that of protein particles, were prepared on a modified milling machine, followed by filtration to enrich particles of interest. A representative ETFE standard set was prepared, which could be quantitatively evaluated by flow imaging, automatic visual inspection, in addition to manual visual inspection. Studies indicated that the ETFE particles in solution better mimic the appearance and behavior of protein particles than commonly used polystyrene microsphere standards and therefore could be a viable standard for inherent protein particles. Such standards could be used during formulation development and to non-destructively identify potential stability problems. They can also be used to develop a more consistent, standardized practice of visual inspection in the industry.
PDA Journal of Pharmaceutical Science and Technology


protein aggregation, visible particles, inherent visible particles, proteinaceous, particle standard, ethylene tetrafluoroethylene, particle surrogate


Telikepalli, S. , Gonzalez, K. , Dragulin-Otto, S. , Ripple, D. , Carrier, M. and Khan, M. (2019), Development of Protein-Like Reference Material for Semi-Quantitatively Monitoring Visible Proteinaceous Particles in Biotherapeutics, PDA Journal of Pharmaceutical Science and Technology, [online], (Accessed May 25, 2024)


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Created June 17, 2019, Updated May 4, 2021