Paul Wuh-Liang Hwu, MD, PhD, National Taiwan University Hospital, Taipei, Taiwan, describes the rationale and ongoing research into gene therapy for aromatic l-amino acid decarboxylase (AADC) deficiency. AADC deficiency is a very rare genetic disorder caused by mutations in the dopa decarboxylase gene leading to reduced AADC enzyme activity, resulting in delayed cognitive and speech development. Dr Hwu describes the study of eladocagene exuparvovec, a recombinant adeno-associated viral vector (AAV) serotype 2 carrying cDNA encoding the human AADC gene, which is administered via bilateral infusion to the putamen. Results demonstrate the efficacy of this treatment in improving cognition and motor development. This interview took place at the European Society of Gene & Cell Therapy (ESGCT) Virtual Congress 2021.