Gene therapy targeting the GBA1 gene using an AAV-9 vector (PR001A) for use in GBA-PD is currently in Phase I, the PROPEL study, being tested for the safety of intra-cisternal administration in PD patients with at least one pathogenic GBA1 mutation (Prevail Therapeutics; NCT04127578), while there are currently three ongoing phase II studies targeting GCase. The gene discussed is GBA1; the disease is Parkinson disease.