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From the Departments of Neurology (C.W.C., K.S.B., M.J.A.), Neurological Surgery (P.A.S., P.S.L., K.S.B.), and Radiology and Biomedical Imaging (R.A.H., H.F.V.), University of California, San Francisco, CA; The Michael J. Fox Foundation for Parkinson's Research (J.L.E.), New York, NY; Department of Molecular Imaging and Neuroscience, Lawrence Berkeley National Laboratory, and Helen Wills Neuroscience Institute (W.J.J.), University of California, Berkeley, CA; University of Pennsylvania School of Medicine (J.F.W.), Philadelphia, PA.
* To whom correspondence should be addressed. E-mail: aminoffm{at}neurology.ucsf.edu.
Background: In Parkinson disease (PD), the benefit of levodopa therapy becomes less marked over time, perhaps because degeneration of nigrostrial neurons causes progressive loss of aromatic L-amino acid decarboxylase (AADC), the enzyme that converts levodopa into dopamine. In a primate model of PD, intrastriatal infusion of an adeno-associated viral type 2 vector containing the human AADC gene (AAV-hAADC) results in robust response to low-dose levodopa without the side effects associated with higher doses. These data prompted a clinical trial.
Methods: Patients with moderately advanced PD received bilateral intraputaminal infusion of AAV-hAADC vector. Low-dose and high-dose cohorts (5 patients in each) were studied using standardized clinical rating scales at baseline and 6 months. PET scans using the AADC tracer [18F]fluoro-L-m-tyrosine (FMT) were performed as a measure of gene expression.
Results: The gene therapy was well tolerated, but 1 symptomatic and 2 asymptomatic intracranial hemorrhages followed the operative procedure. Total and motor rating scales improved in both cohorts. Motor diaries also showed increased on-time and reduced off-time without increased "on" time dyskinesia. At 6 months, FMT PET showed a 30% increase of putaminal uptake in the low-dose cohort and a 75% increase in the high-dose cohort.
Conclusion: This study provides class IV evidence that bilateral intrastriatal infusion of adeno-associated viral type 2 vector containing the human AADC gene improves mean scores on the Unified Parkinson's Disease Rating Scale by approximately 30% in the on and off states, but the surgical procedure may be associated with an increased risk of intracranial hemorrhage and self-limited headache.
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