Interim results from a Phase Ib trial show that gene therapy may reduce the need for medication in patients with Parkinson’s disease refractory to levodopa. The investigational therapy is designed to insert the gene for aromatic 1-amino acid decarboxylase (AADC) – which converts levodopa to dopamine – directly into the striatum of patients using MRI guidance.
The trial enrolled three cohorts of five patients each, which received escalating doses of the gene therapy AAV-AADC (VY-AADC01, Voyager Therapeutics).
Analysis after 12–36 months of follow-up suggest that the therapy is well tolerated. There were no reports of vector-related serious adverse events.
Further, the treatment seemed effective at reducing the symptoms of Parkinson’s disease. By 12 months, mean levodopa equivalent dose (LED) reductions of -10.2%, -32.8% and -39.3% were observed for cohorts 1, 2 and 3, respectively. Principal investigator Dr Chad Christine commented: “We were impressed by how well the decrease in need for antiparkinsonian medications paralleled the AADC activity we measured in the putamen of our subjects, which is consistent with the proposed mechanism of action of VY-AADC01.” Patients also reported improvements in Parkinson’s disease ‘ON’ and ‘OFF’ times; impressively, these improvements were maintained for up to 36 months.
While the small sample size and open-label design may limit the generalisability of these findings, the new treatment shows promise for enhancing the efficacy of levodopa in Parkinson’s disease. The clinical efficacy of the treatment is being more thoroughly investigated in a recently started Phase II randomised trial.
Larson et al. VY-AADC01 gene therapy in Parkinson’s disease: Interim results of the on-going Phase 1b PD-1101 trial. Mov Disord. 2018; 33 (suppl 2): Abstract 315. Accessed 28 November 2018 at: http://www.mdsabstracts.org/abstract/vy-aadc01-gene-therapy-in-parkinsons-disease-interim-results-of-the-on-going-phase-1b-pd-1101-trial/
Brunk. Investigational gene therapy for medically refractory Parkinson’s shows promise. Clinical Neurology News 2018. Accessed 28 November 2018 at: https://www.mdedge.com/clinicalneurologynews/article/178332/movement-disorders/investigational-gene-therapy-medically