Gene therapy for AADC deficiency
Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare genetic neurological disorder caused by autosomal recessive inherited pathogenic mutants of the DDC gene, which prevents the conversion of L-3,4-dihydroxyphenylalanine (L-DOPA) into dopamine (DA) that leads to decreased availability of serotonin and dopamine in the presynaptic and synaptic cleft, as well as a deficiency of catecholamines. AADC deficiency results in movement disorders including hypokinesia, dystonia, and oculogyric crisis, along with behavioral problems, autonomic dysfunction, and developmental delay. The rationale for intraputaminal AADC gene therapy is to deliver a functional copy of the human DDC gene (hAADC) with a recombinant adeno-associated virus type 2 (AAV2) vector directly to striatal regions impacted by the disease, which subsequently leads to increased conversion of levodopa to DA in targeted striatal neuronal cell bodies. Patients received AAV2-hAADC infused bilaterally into the putamen. The procedure and treatment were well tolerated. An increase in dopamine production could be demonstrated by positron emission tomography and neurotransmitter analysis.