Over time, clinical trials of AAV2‐AADC in PD have increased vector volumes, infusion rates, and vector genome dosages from 9 × 1010 vg in 200 μL initially to 4.7 × 1012 vg in 900 μL in the most recent trial, with the aim of increasing putaminal coverage.30, 35. Here, DDC is linked to Parkinson disease.