Acadia Pharmaceuticals Shares Fall After RADIANT Phase 2 Study Misses Primary Endpoint

Acadia Pharmaceuticals Inc. (NASDAQ:ACAD) shares fell 6% after the company reported results from its Phase 2 RADIANT study of remlifanserin in Alzheimer’s disease psychosis, with the trial missing its primary endpoint while meeting a key secondary measure at nominal statistical significance.

The study evaluated 30 mg and 60 mg once-daily doses of remlifanserin against placebo.

On the primary SAPS H+D endpoint, the 60 mg dose produced a change from baseline of -12.6 at week six, compared with -10.4 for placebo. The result had a p-value of 0.0603 and therefore did not meet the study’s primary endpoint. The standardised effect size was 0.26.

Secondary Endpoint Shows Nominal Statistical Significance

On the key secondary CGI-S-ADP endpoint, which measured Clinical Global Impression-Severity, the 60 mg dose produced a change from baseline of -1.3 at week six, compared with -0.9 for placebo.

The result had a p-value of 0.0077 and a standardised effect size of 0.37.

The company described the result as nominally statistically significant. A secondary-endpoint result does not change the fact that the study did not meet its primary endpoint.

The 30 mg dose showed minimal improvement compared with placebo across the evaluated endpoints.

Acadia Continues Phase 3 Programme

Acadia said it plans to continue enrolment in two ongoing Phase 3 studies evaluating remlifanserin for Alzheimer’s disease psychosis.

However, the company plans to remove the 30 mg dose arm from the development programme following the Phase 2 results.

The continuation of the Phase 3 trials represents the company’s development plan and does not establish that the investigational treatment will demonstrate efficacy in those studies or receive regulatory approval.

Safety Findings Reported Across Both Doses

Acadia reported that adverse events, serious adverse events and treatment discontinuations resulting from adverse events occurred at similar rates in the remlifanserin and placebo groups.

The company said there was no observed signal of QT prolongation compared with placebo and no negative effect on motor symptoms or cognition. No deaths were reported in the remlifanserin treatment groups.

These findings relate to the safety observations from the Phase 2 study and are separate from the trial’s efficacy results.

Acadia plans to present more detailed findings from RADIANT at the Clinical Trials on Alzheimer’s Disease conference in Boston from November 16 to 19, 2026.

The company is also evaluating remlifanserin in a separate Phase 2 study for Lewy body dementia psychosis.

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