Acadia falls after Alzheimer's-related drug narrowly misses goal in study

** Acadia Pharmaceuticals ACAD.O shares fall 15.6% to $21.45 premarket

** Co says its experimental drug remlifanserin narrowly missed main goal in mid-stage trial

** The study tested remlifanserin for the treatment of hallucinations and delusions associated with Alzheimer's disease psychosis (ADP)

** Company says trends suggest continuing development of 60 mg once-daily dose in ADP

** Acadia plans to continue enrolling its two ongoing late-stage studies evaluating remlifanserin in ADP

** Alzheimer's disease psychosis involves experiencing hallucinations and delusions driven by physical brain changes

** Up to last close, stock down ~5% YTD