USP adds CryoTEM to AAV8 reference standard certificates

By AI, Created 8:40 AM UTC, May 20, 2026, /AGP/ – The U.S. Pharmacopeia has recognized cryo-transmission electron microscopy as a new analytical method on its updated AAV8 reference standard certificates, expanding the tools available for characterizing empty, full and intermediate capsids in gene therapy vectors. The move strengthens a global shift toward direct particle-level analysis for AAV quality control and follows earlier recognition from the British Pharmacopoeia.

Why it matters: - CryoTEM adds a direct visualization method for measuring AAV capsid populations, including empty, full, intermediate and overfull particles. - The update gives developers and manufacturers another reference point for a critical quality attribute that affects the safety and efficacy of AAV-based gene therapies. - Broader recognition from both USP and the British Pharmacopoeia points to a growing consensus that CryoTEM is moving from characterization into routine quality control.

What happened: - The U.S. Pharmacopeia updated its AAV8 reference standard certificates to include CryoTEM as an analytical method. - The updated certificates cover AAV8 (Empty Capsids) and AAV8 (Full Capsids). - QuTEM said the recognition is based on a multi-laboratory study of six methods for measuring empty and full capsids. - The prior certificates used five orthogonal methods: AUC, SEC-MALS, CDMS, mass photometry and UV spectroscopy. - CryoTEM is now the only newly added method in the update.

The details: - CryoTEM classifies individual particles by internal density rather than inferring content from indirect biophysical signals. - The method is relatively unaffected by debris and aggregation, which supports use in complex sample matrices. - The updated certificates include CryoTEM micrographs and population distribution data for both AAV8 standards. - The measurements were acquired on a Glacios cryo-electron microscope at 200 kV using undiluted samples. - For AAV8 (Full Capsids), CryoTEM resolved 89% full, 3% intermediate, 5% empty and 3% overfull. - For AAV8 (Empty Capsids), CryoTEM confirmed 98% empty and cross-verified the values from the five orthogonal methods. - CryoTEM will also be referenced in USP general chapter <1067>, “Best Practices for the Manufacture and Quality Control of Recombinant Adeno-Associated Virus Gene Therapy Products.” - That chapter becomes official on Aug. 1, 2026.

Between the lines: - The USP update signals that reference standards are evolving toward methods that can distinguish closely related capsid states with more granularity. - Direct imaging matters because partial fills and overfull particles can be difficult to resolve with indirect assays alone. - QuTEM’s role in validated workflows suggests the company is positioning CryoTEM for routine QC and release testing, not just research use. - The British Pharmacopoeia’s earlier recognition adds pressure for wider harmonization across major pharmacopeias.

What’s next: - USP’s general chapter <1067> will formalize CryoTEM as an orthogonal method for distinguishing empty, full and partially filled capsids when it becomes official in August. - The dual USP and British Pharmacopoeia recognition may accelerate adoption of CryoTEM in QC and GMP-regulated environments. - QuTEM said it expects the platform to support consistent analytics at QC scale as more gene therapy programs rely on AAV characterization.

The bottom line: - USP’s addition of CryoTEM marks a notable shift toward particle-level AAV analysis in reference standards and quality control.