A native mass spectrometry-based assay for rapid assessment of the empty/full capsid ratio in AAV gene therapy products

Adeno-associated virus (AAV)-based cell and gene therapy is a rapidly developing field, requiring analytical methods for detailed product characterization. One important quality attribute of AAV products that requires monitoring is the amounts of residual empty capsids following downstream processing. Traditionally, empty and full particles are quantified via analytical ultracentrifugation as well as anion exchange chromatography using ultraviolet or fluorescence detection. Here, we present a native mass spectrometry-based approach to assess the ratio of empty to full AAV-capsids without the need for excessive sample preparation. We report rapid determination of the amount of empty particles in AAV5 and AAV8 samples, with results correlating well with more conventional analysis strategies, demonstrating the potential of state-of-the-art mass spectrometry for the characterization of viral particles.