2023 FDA Science Forum
Analytical method development to characterize subvisible particles using morphologically directed Raman spectroscopy
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Contributing OfficeCenter for Drug Evaluation and Research
Abstract
Particles are a critical quality attribute of injectable protein therapeutics having potential risks associated with drug safety and efficacy. Particles are categorized into visible (> 100 µm), subvisible (1-100 µm), submicron (100-1000 nm), and nanometer (<100 nm) particles. Particles could be proteinaceous and non-proteinaceous in composition with various shapes. To control subvisible particles (SVP) in protein therapeutics, it is important to evaluate particle size, shape, and composition as well as the size distribution and counts. The current compendial method Light Obscuration (LO) and its orthogonal methods such as Flow Imaging Microscopy (FIM) and Membrane Microscopy (MM) have been routinely utilized to analyze SVPs in protein therapeutics for lot release based on USP guidelines. Though the compendial methods can provide information on the particle size, shape, and count, none of them can distinguish particle composition or identification. Herein, we introduce a novel analytical tool, morphologically directed Raman spectroscopy (MDRS), for SVP characterization. The benefit of this method is that particles can be identified based on its Raman spectrum along with particle size, shape, and size distribution. Three particle standards – polystyrene beads, a traditional particle standard currently used in industry, and SU-8 and ETFE, new particle standards developed by NIST – were used for method development. The new standards have been developed by NIST as proteinaceous particle surrogates to support the development of SVP analysis methods by having appropriate standards. In our study, MDRS rendered high resolution images for ETFE standard (> 90%) ranging from 19 μm to 100 μm, covering most SVP range, and generated more accurate or comparable physical property evaluation data to FlowCam. Our data also reported that among all the standards, ETFE particle standard showed the closest morphology to proteinaceous particles. After establishing the feasibility of the MDRS method and appropriate standards, we analyzed proteinaceous SVPs. To our knowledge, this is the first report of characterizing proteinaceous SVPs in protein therapeutics through individual particle identification using MDRS. Our study shows that MDRS may contribute to improve the current SVP analysis system in protein therapeutics quality control.
