Acadia Pharmaceuticals has received US FDA Fast Track designation for remlifanserin, an investigational 5-HT2A receptor inverse agonist for Alzheimer’s disease psychosis, as the company prepares to report Phase II data from its RADIANT program later this year. There are currently no US FDA-approved therapies specifically for hallucinations and delusions associated with Alzheimer’s disease psychosis.

Fast Track status allows Acadia more frequent interaction with the FDA during development and the option of rolling submission of a future new drug application, but it does not alter the clinical bar the RADIANT program must clear. What makes the timing notable is that the designation was granted while Phase II enrollment has just closed and before any efficacy data have been disclosed — meaning the FDA’s decision rests on the severity of Alzheimer’s disease psychosis and the absence of approved options, not on RADIANT results themselves. Acadia has said screening and enrollment in the Phase III portion of the operationally seamless RADIANT design are already underway, a structure intended to let the company move from Phase II to Phase III without a gap for trial initiation.

Alzheimer’s disease psychosis, characterized by hallucinations and delusions in patients with the underlying dementia, has no drug specifically approved for it in the United States. Acadia’s approved product pimavanserin (Nuplazid), a chemically related 5-HT2A inverse agonist, holds approval only for hallucinations and delusions associated with Parkinson’s disease psychosis, granted in April 2016. Physicians treating Alzheimer’s disease psychosis today rely on off-label use of atypical antipsychotics, a class associated with sedation, motor side effects, and cardiac risk in elderly patients — concerns that inform how remlifanserin’s profile is being positioned.

Acadia has previously reported Phase I safety and pharmacokinetic data for remlifanserin and reaffirmed that topline Phase II results from RADIANT are expected between September and October 2026.

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