A Study to Evaluate the Effects of SAGE-718 in Participants With Parkinson's Disease Cognitive Impairment

A Randomized, Double-blind, Placebo-controlled Study to Evaluate the Effects of SAGE-718 in Parkinson's Disease Cognitive Impairment

The primary purpose of this study is to evaluate the effect of SAGE-718 on cognitive performance in participants with Parkinson's disease mild cognitive impairment (PD-MCI).

Inclusion Criteria:

1. Meet the following criteria for PD-MCI: Have a confirmed diagnosis of idiopathic Parkinson's disease (PD) according to 2015 Movement Disorder Society (MDS) clinical diagnostic criteria and meet MDS Task Force criteria for MCI in PD (excluding requirement for United Kingdom PD Brain Bank diagnostic criteria).
2. Meet the following criteria for Montreal Cognitive Assessment (MoCA): For participants meeting Level 1 PD-MCI criteria, have a MoCA score of 20 to 25 (inclusive) at Screening; For participants meeting Level 2 PD-MCI criteria (within the past year), have a MoCA score of 18 to 25 (inclusive) at Screening.
3. Meet criteria for modified Hoehn & Yahr Stage I to III (mild to moderate motor severity) at Screening.
4. Have stable motor symptoms for at least 4 weeks prior to Screening, in the opinion of the investigator.
5. Must be able to complete the Color Trails Test 1 (including the ability to follow rater redirection and correct errors), and, based on participant's performance and investigator's opinion, participant is expected to be capable of engaging in prolonged cognitive testing for the duration of the study.

Exclusion Criteria:

1. Have a diagnosis of dementia of any etiology, including but not limited to: Dementia with Lewy bodies, Alzheimer's dementia, and vascular dementia.
2. Have any parkinsonism other than PD, including secondary parkinsonism or atypical parkinsonism.
3. In the opinion of the investigator, be experiencing fluctuations in motor symptoms associated with PD that will interfere with completing study procedures.
4. Have an ongoing central nervous system condition other than PD that in the opinion of the investigator could influence the outcome of the study.
5. Have experienced significant psychotic symptoms, including hallucinations or delusions, within the past 3 months, in the opinion of the investigator.
6. Have a history of brain surgery, deep brain stimulation, or any history of hospitalization due to a brain injury.
7. Have a history, presence, and/or current evidence clinically relevant intracranial abnormality (e.g., stroke, hemorrhage, space-occupying lesion).