Although there are still no clinical studies specifically focused on combating LIDs through gene therapy, there are clinical trials employing AAV2-AADC or AAV2-glial-derived neurotrophic factor (GDNF) in PD that have shown improvement in L-DOPA response (ON time) without increasing dyskinesias [114,115,116] (NCT01973543). This evidence concerns the gene DDC and Parkinson disease.