GAD1 and Parkinson disease: An open-label study in 12 patients with advanced PD followed over a 12-month period after unilateral injections of AAV-GAD into the STN, demonstrated a significant improvement in UPDRS scores, expressed predominantly on the side of the body contralateral to the surgery and were seen after 3 months and persisted up to 12 months after gene therapy (Kaplitt et al., 2007).