TH and GTPCHI gene therapy for Parkinson's disease

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This proposal brings together three experienced groups proposing an integrated series of experiments using adeno-associated virus (Gainesville) in rodent (Lund) and nonhuman primate (Rush) models of Parkinson's disease (PD). A concensus is emerging that site-specific rAAV-mediated striatal L-dopa delivery might be a useful strategy for treating PD. However, clinical trials using this approach cannot even begin to be considered before critical efficacy and safety studies need to be performed. Towards this end, three research themes will be explored in this application. First we will perform studies in monkeys designed at vector optimization. We will determine the optimal AAV serotype in nonhuman primates and establish the optimal ratio of TH to GTPCH1.Currently, a 1:1 ratio is utilized. However, we believe that a higher ratio will be more effective due to the kinestics of GTPCH1 and thus we will be able to deliver more TH, and ultimately more LDOPA. These studies will also provide critical "scaling-up" data in primates that will be relevant for futures clinical trials. The second research theme is efficacy. The TH/GTPCH1 gene delivery approach has already been shown to be effective in reversing drug-induced and spontaneous motor deficits in rodent models of PD. The present proposal will establish efficacy in MPTP treated monkeys, the best animal model available for PD. The third aim is safety. With regards to functional safety, our main concern is dyskinesias. We have already demonstrated that rAAV-Ldopa reverses already manifest dyskinesias in 6-OHDA lesioned rats and have new data demonstrating that rAAV-LDOPA prevents the emergence of dyskinesias. IN this new application, we will evaluate the role of serotonin in the expression of dyskinesias in rats. Further, the effect of "hot spot" versus "widespread" delivery of TH/GTPCH1 upon efficacy and dyskinesias will be evaluated. The monkey model of dyskinesias is recognized as the best available for the study of dyskinesias. In the present study we will test the hypothesis that gene delivered levodopa can both reverse already manifest Idopa dyskinesias and delay the emergence of new dyskinesias. These studies will determine the safety and efficacy of gene delivery of LDOPA and determine whether this approach is appropriate for clinical trials.