Cryo-transmission electron microscopy (CryoTEM) has been recognized as a new analytical method on the U.S. Pharmacopeia's (USP) updated AAV8 reference standard certificates. The update is based on a comprehensive multi-laboratory study of six methods for measuring empty and full capsids, and adds CryoTEM alongside the five existing orthogonal methods: AUC, SEC-MALS, CDMS, mass photometry, and UV spectroscopy.
Unlike the other methods, CryoTEM directly visualizes individual particles — classifying each capsid based on internal density rather than inferring content from indirect biophysical signals. Because the technique is relatively unaffected by debris and aggregation, it supports accurate classification even in complex matrices.
Recognition by both USP and British Pharmacopoeia
This USP recognition follows earlier recognition by the British Pharmacopoeia (BP), which discusses CryoTEM in its ATMP Guidance on Characterisation of the Capsid Particle Population in rAAV Products. The BP highlights CryoTEM's accuracy, precision, and robustness as suitable for implementation in QC and GMP-regulated environments. Together, the dual recognition reflects a growing global consensus that CryoTEM is becoming an essential tool in the AAV analytical toolkit.
- U.S. Pharmacopeia (USP): listed on AAV8 reference standard certificates (Cat. No. 1000301 & 1000302). Referenced in USP general chapter <1067>, effective August 1, 2026.
- British Pharmacopoeia (BP): Recognized in ATMP Guidance on rAAV capsid characterization as accurate, precise, and robust for QC and GMP-regulated environments.
Why this matters for gene therapy developers
The distribution of full, partially filled, empty, and overfull capsids in an AAV product is a critical quality attribute (CQA) that directly affects the safety and efficacy of the therapy. Accurate, comparable measurement of these populations across laboratories has historically been limited by gaps in method harmonization and reference materials.
USP's inclusion of CryoTEM on the AAV8 certificates now gives developers and manufacturers a common, pharmacopoeia-backed foundation for vector-content characterization — supporting its use in regulatory submissions, IND filings, and quality release testing.
CryoTEM for AAV characterization at QuTEM
As a pioneer in quantitative CryoTEM for biopharmaceutical applications, QuTEM has validated the underlying platform and built the automated workflows that make the technique robust enough for routine QC use and release testing. Our GMP-certified CryoTEM services deliver particle-level resolution of capsid content — whether you are preparing an IND submission, optimizing manufacturing, or running quality release on an AAV8 product.
CryoTEM is now ready for routine QC use and release testing, with automated workflows and a validated platform that classify every capsid as full, intermediate, empty, or overfull at a level of detail that indirect biophysical methods simply cannot match.
– Josefina Nilsson, CEO at QuTEM
See full press release here.
