Acadia Pharmaceuticals Inc. reported Phase 2 results Tuesday for remlifanserin, an experimental 5HT2A receptor inverse agonist being developed for psychosis in Alzheimer's disease and Lewy body dementia, after the drug's 60 mg once-daily dose narrowly missed its primary efficacy endpoint.
In the RADIANT trial, which evaluated remlifanserin for hallucinations and delusions associated with Alzheimer's disease psychosis, the 60 mg arm recorded a SAPS H+D change of −12.6 versus −10.4 for placebo at week 6, yielding a standardized effect size of 0.26 and a p-value of 0.0603 — just outside conventional statistical significance.
The key secondary endpoint, CGI-S-ADP, did achieve nominal significance, with a p-value of 0.0077. Patients on the 60 mg dose showed a change of −1.3 versus −0.9 for placebo at week 6, producing a standardized effect size of 0.37.
The 30 mg dose arm showed minimal improvement compared with placebo across all measured endpoints. Acadia plans to amend the study protocol to remove the 30 mg dosage arm going forward.
On safety, remlifanserin demonstrated a profile similar to placebo at both doses, with comparable rates of adverse events, serious adverse events and discontinuations. There was no signal of QT prolongation versus placebo, and no deaths occurred in the remlifanserin treatment groups.
Acadia said it will continue enrolling its two ongoing Phase 3 studies of remlifanserin. Detailed data from the Phase 2 trial are expected to be presented at the Clinical Trials on Alzheimer's Disease conference, November 16–19, 2026, in Boston.
Roughly 30% of the more than 7 million people living with Alzheimer's disease in the United States experience psychosis, and no FDA-approved therapy currently exists for the indication.
