It refers to patent claims covering how the immune system responds to viral vectors like AAV, and to methods that allow a second or later dose to work despite that response. This includes capsid engineering to reduce neutralizing antibody binding, immunosuppression regimens administered around dosing, seroprevalence testing to screen patients beforehand, and empty capsid decoy strategies that absorb existing antibodies. The 12,584 records in this landscape combine these approaches with underlying antibody and complement-activation science.

Filings concentrate at the top: the five leading assignees together hold 21.5% of the 12,584 records in scope, and the top ten hold 31.0%. The ranking includes large biopharmaceutical companies, an academic technology-transfer program, and specialist developers of nanocarrier and immunosuppression platforms. Beyond the leaders, filings spread across a long tail of companies with only a handful of records each, meaning the field is not a closed monopoly.

Filings peaked in 2021 at 1,021 and fell to 524 by 2024, a 49% decline over that span. That decline should be read carefully: publication typically lags filing by around 18 months, so 2025 and 2026 figures in this dataset are still incomplete and cannot yet be treated as evidence of a continued slowdown. The 2017-2021 run-up shows the field was still actively expanding claim coverage through that period.