This study will test SAGE-718 to evaluate cognitive effects in subject with early manifest HD. The subject will be on study drug or placebo for 84 days. At clinic visits, participants will take the IP under staff supervision, followed
by assessments of cognitive function, health-related function and quality of life, and neuropsychiatric symptoms.

This study is an open-label study that will evaluate SAGE-718 on the cognitive effects in subject with early manifest Huntington's Disease (HD). The subject will be on study drug for a year. At clinic visits, participants will take the IP under staff supervision, followed by assessments of cognitive function, health-related function and quality of life, and neuropsychiatric symptoms.

The purpose of this clinical trial is to evaluate the safety and efficacy of BIA-28-6156 in subjects with Parkinson's Disease (PD). BIA -28-6156 is an investigational drug meaning that its safety, effects and how it works are still being studied. This is a randomized (assigned by chance), placebo-controlled study, which means that some participants will receive a fake treatment (placebo) while others get the real treatment. The placebo treatment looks like the BIA-28-6156 medications but doesn't contain any active ingredient. The medication is in a pill form and will be administered orally. This research is also double blind, meaning that neither the participants nor the researcher will know which treatment they will be receiving. In Part A of this study, participants will be asked to give a blood sample for a genetic screening test. If genetic testing in part A indicates the person can participate, they may be asked to volunteer for part B. Duration of Part B is about 87 weeks, this includes 5 weeks for screening, 78 weeks for the double-blind treatment period, and 4 weeks for follow up. There are at least 11 visits in total in 20 months (9 clinic visits, 2 remote phone/video visits); this does not include unscheduled visits. During visits, participants should anticipate tests including electrocardiograms (ECGs), vitals measurements (including temperature, blood pressure, and heart rate), and a physical/neurological examination. Some of the risks includes fatigue, headache, drowsiness, muscle aches and possible worsening of PD symptoms. As for benefits, participants who receives the BIA drug may see their PD progression slowing.

This study is intended to determine the efficacy and safety of the study drug AMX0035 in people living with Progressive Supranuclear Palsy (PSP). Participants will between the ages of 40 and 80 and will be randomized to receive AMX0035 or placebo. Study participation will last 52 weeks with 7 visits to the clinic. After study participation ends, there is the option for the participant to continue into the open-label extension period where they would receive AMX0035 for another 56 weeks.