Terazosin And Metabolic Engagement in Parkinson's Disease

To assess target engagement of terazosin (TZ) at multiple doses (1 mg/day, 3 mg/day, and 5 mg/day) and to assess sustained target engagement over 6 months relative to placebo in patients with Parkinson's Disease (PD). Target engagement will be measured using a whole blood luminescence assay to quantify Adenosine Triphosphate (ATP) and a plasma metabolomics assay. A subset of randomized participants will also undergo imaging studies to quantify cerebral ATP using 31P-magnetic resonance spectroscopy (31P-MRS) and 18F-fluurodeoxyglucosed positron emission tomography (18F-FDG PET) to assess changes in glucose uptake in response to TZ. The investigators will compare the mean change from baseline in these assays between the TZ and placebo groups. The null hypothesis to be tested is that TZ does not engage its target (phosphoglycerate kinase 1, or PGK1) and does not lead to increases in the outcome variables of interest. A total of 100 patients with early PD will be recruited. Participants will be randomized to TZ or placebo in a 60:40 fashion to account for predicted dropouts in the TZ group. Study treatment will be administered for 26 weeks, followed by a four-week washout period.