This landscape covers 871 patent records filed between 2015 and mid-2026 that describe methods for distinguishing genome-containing (full) AAV capsids from empty shells, including anion exchange chromatography, salt gradient elution, analytical ultracentrifugation reference methods and caesium chloride gradient techniques. Most records also carry claims in adjacent classes such as A61K medicinal preparations and C12N genetic engineering, since separation methods are typically claimed alongside the biologic product itself. No single assignee holds a majority of this space, so a freedom-to-operate review needs to look across a genuinely long list of filers rather than a handful of dominant players.

One assignee leads the ranking with 72 of the 871 records in scope, a clear step ahead of the fifth-ranked holder at 25 records and the tenth-ranked holder at 20. Beyond the top ten, which together hold 35.7% of all records, filing activity spreads across a ranking that runs to 100 companies, most holding only a small number of records. Several of the historically active leaders show no filings in the most recent year, though this partly reflects the roughly 18-month lag between filing and publication rather than a genuine stop in activity.

Filing activity around this corpus, which is built substantially on anion exchange chromatography search terms, peaked at 68 records in 2021 and has declined since, with 2022 sitting at only 14 records. That pattern is consistent with a technology where the foundational chromatography methods were staked out earlier and later filers are refining wash solutions, gradient parameters and specific protein targets rather than filing broad new base methods. The most recent year's figures are necessarily incomplete due to publication lag, so the true 2025-2026 filing rate is understated in the raw trend.

Both are reference techniques named explicitly in this patent corpus for determining the ratio of full to empty AAV capsids, and both appear as search terms tied to specification and yield-loss claims rather than as a single dominant method. Analytical ultracentrifugation is generally used as an orthogonal, higher-resolution reference standard against which faster methods like anion exchange chromatography are validated. Caesium chloride gradient centrifugation is an older density-based separation approach; patent activity naming it sits alongside newer chromatography-based claims, suggesting both remain referenced in current specification and quality-control filings rather than one having fully displaced the other.

The clearest gap sits between the volume of biological composition claims and the volume of separation-process claims: C07K peptide and protein claims cover 63.9% of the 871 records while B01D separation-process claims cover only 20.9%, and G01N analytical-testing claims sit at just 9.1%. That imbalance points toward process-parameter refinements, in-line ratio monitoring instrumentation, and salt-gradient optimisation as areas with comparatively less claim density. A new filer targeting these process-and-analytics branches, rather than re-claiming capsid biology already covered by leading assignees, is more likely to find open ground.