This study seeks to evaluate safety and efficacy of Nelotanserin for the treatment of visual hallucinations in subjects with Lewy body dementia.

This is a double-blind, randomized, placebo-controlled, cross-over study in subjects with Lewy body dementia who experience frequent visual hallucinations.

Subjects who meet the randomization criteria enter the double-blind treatment period.

Each subject will be randomized 1:1 to one of the 2 treatment sequences: Nelotanserin in the first treatment period followed by placebo in the second treatment period, or placebo in the first treatment period followed by Nelotanserin in the second treatment period.

Inclusion Criteria:

• Adult subjects at least 50 years of age, with a diagnosis of LBD based on DSM-5 diagnostic criteria or diagnosis of Parkinson's disease dementia (PDD) based on DSM-5 diagnostic criteria;
• Presence of frequent visual hallucinations
• Mini Mental State Examination score ≥ 18

Exclusion Criteria:

• Subjects have a current diagnosis of significant psychotic disorders including, but not limited to, schizophrenia or bipolar disorder
• Subjects' psychotic symptoms are secondary to or better accounted for by another medical condition, psychiatric disorder, or substance abuse
• Subjects with a current serious and/or unstable cardiovascular, respiratory, thyroid, gastrointestinal, renal, hematologic or other medical disorder