Key Highlights

  • ACADIA Pharmaceuticals closed down 6.76% at $20.68 despite its 60 mg remlifanserin dose improving key Alzheimer's disease psychosis measures versus placebo.
  • The 60 mg dose produced a SAPS-H+D change of -12.6 versus -10.4 for placebo at week 6, with an effect size of 0.26.
  • ACADIA plans to continue Phase Three enrollment, remove the lower-dose arm, and present detailed findings at the CTAD conference in November.

ACADIA Pharmaceuticals (NASDAQ:ACAD) closed down 6.76% at $20.68 even as its remlifanserin program produced Phase Two topline results in Alzheimer's disease psychosis, with the 60 mg dose showing greater improvement than placebo on the primary measure at week 6. The data matter because ACADIA plans to continue Phase Three enrollment, remove the lower-dose arm, and present detailed findings at CTAD.

60 mg Dose Shows Greater Improvement

The primary SAPS-H+D measure recorded a -12.6 change from baseline for once-daily 60 mg remlifanserin, compared with -10.4 for placebo. The standardized effect size was 0.26, with p=0.0603. On the CGI-S-ADP secondary measure, the treatment change was -1.3 versus -0.9 for placebo, producing an effect size of 0.37 and p=0.0077. The separation from placebo increased through the six-week treatment period, while the lower dose showed minimal improvement across the endpoints.

Safety Profile and Next Steps

Across both doses, adverse-event rates, serious adverse-event rates, and discontinuations due to adverse events were similar to placebo. Detailed safety and efficacy findings are planned for an oral presentation at the Clinical Trials on Alzheimer's Disease conference in Boston, scheduled for November 16-19, 2026, while a separate Phase Two study is evaluating remlifanserin in Lewy body dementia psychosis. ACADIA plans to continue enrolling two ongoing Phase 3 Alzheimer's disease psychosis studies, including removal of the 30 mg dosage arm.