Developing an Anion Exchange Chromatography Assay for Determining Empty and Full Capsid Contents in AAV6.2

Chunlei Wang; Sri Hari Raju Mulagapati; Zhongying Chen; Jing Du; Xiaohui Zhao; Guoling Xi; Liyan Chen; Thomas Linke; Cuihua Gao; Albert E Schmelzer; Dengfeng Liu

doi:10.1016/j.omtm.2019.09.006

Developing an Anion Exchange Chromatography Assay for Determining Empty and Full Capsid Contents in AAV6.2

Mol Ther Methods Clin Dev. 2019 Sep 26:15:257-263. doi: 10.1016/j.omtm.2019.09.006. eCollection 2019 Dec 13.

Authors

Affiliations

¹ Analytical Sciences, Biopharmaceutical Development, BioPharmaceuticals R&D, AstraZeneca, One MedImmune Way, Gaithersburg, MD 20878, USA.
² Purification Process Sciences, Biopharmaceutical Development, BioPharmaceuticals R&D, AstraZeneca, One MedImmune Way, Gaithersburg, MD 20878, USA.
³ Antibody Discovery and Protein Engineering, R&D, AstraZeneca, One MedImmune Way, Gaithersburg, MD 20878, USA.
⁴ Cell Culture and Fermentation Sciences, Biopharmaceutical Development, BioPharmaceuticals R&D, AstraZeneca, One MedImmune Way, Gaithersburg, MD 20878, USA.

Abstract

Adeno-associated virus (AAV) vectors are clinically proven gene delivery vehicles that are attracting an increasing amount of attention. Non-genome-containing empty AAV capsids are by-products during AAV production that have been reported to potentially impact AAV product safety and efficacy. Therefore, the presence and amount of empty AAV capsids need to be characterized during process development. Multiple methods have been reported to characterize empty AAV capsid levels, including transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), charge detection mass spectrometry (CDMS), UV spectrophotometry, and measuring capsid and genome copies by ELISA and qPCR. However, these methods may lack adequate accuracy and precision or be challenging to transfer to a quality control (QC) lab due to the difficulty of implementation. In this study, we used AAV serotype 6.2 (AAV6.2) as an example to show the development of a QC-friendly anion exchange chromatography (AEX) assay for the determination of empty and full capsid percentages. The reported assay requires several microliters of material with a minimum titer of 5 × 10¹¹ vg/mL, and it can detect the presence of as low as 2.9% empty capsids in AAV6.2 samples. Additionally, the method is easy to deploy, can be automated, and has been successfully implemented to support testing of various in-process and release samples.

Keywords: AAV; AAV6.2; AUC; Anion exchange chromatography (AEC); Chromatography; Empty capsids; High-throughput.