FDA Grants Fast Track Designation to Remlifanserin for Alzheimer Disease Psychosis

In recent news, the FDA granted Fast Track designation to remlifanserin (ACP-204; Acadia Pharmaceuticals), an investigational selective serotonin 5-HT2A receptor inverse agonist, for the treatment of hallucinations and delusions associated with Alzheimer disease psychosis (ADP).¹

“FDA Fast Track designation for remlifanserin underscores the significant unmet need for new treatment options for people living with Alzheimer disease psychosis, a serious condition for which there are currently no FDA-approved therapies,” Catherine Owen Adams, chief executive officer of Acadia, said in a statement.¹ “This is an important milestone for the remlifanserin program, and we look forward to sharing upcoming topline data from the RADIANT Phase 2 trial as we continue to advance remlifanserin as a potential new treatment option for patients and families impacted by this devastating condition.”

The regulatory milestone comes as Acadia advances remlifanserin through the RADIANT development program. Enrollment in the phase 2 portion of the program has been completed, with topline results expected between September and October 2026. Screening and enrollment are also underway in several phase 3 studies as part of RADIANT’s design.

Targeting 5-HT2A Receptors in Alzheimer Disease Psychosis

Remlifanserin is being developed for hallucinations and delusions associated with AD and Lewy body–associated psychosis. Mechanistically, the investigational agent is a potent and highly selective 5-HT2A receptor inverse agonist designed to reduce psychotic symptoms without directly blocking dopamine D2 receptors.

According to Acadia, selective 5-HT2A receptor inverse agonism may address hallucinations and delusions while potentially avoiding some of the safety and tolerability concerns associated with atypical antipsychotics.

RADIANT Program Advances to Phase 3

The RADIANT program is evaluating remlifanserin in patients with ADP across a phase 2/3 development program. The initial phase 2 study was designed as a randomized, double-blind, placebo-controlled trial enrolling approximately 318 patients with ADP over a 6-week treatment period.

Participants were assigned to receive 30 mg or 60 mg of remlifanserin or placebo, with change from baseline on the Scale for the Assessment of Positive Symptoms-Hallucinations and Delusions (SAPS-H+D) total score serving as the primary endpoint.

Following completion of the phase 2 portion, the program is designed to transition into 2 phase 3 studies with identical designs, each planned to enroll approximately 378 patients with ADP. Patients completing the studies will have the option to enter a long-term open-label extension.

With phase 2 enrollment now complete, the upcoming topline readout is expected to provide the next major clinical milestone for the remlifanserin program.

At present, there are no FDA-approved treatments specifically indicated for psychosis in AD, with brexpiprazole and dextromethorphan-bupropion approved for the related but distinct symptom of agitation. If approved, remlifanserin would represent the first therapy specifically indicated for psychosis associated with AD.

REFERENCES
1. Acadia Pharmaceuticals Receives FDA Fast Track Designation for Remlifanserin in Alzheimer's Disease Psychosis. Acadia Pharmaceuticals. News Release. July 20, 2026. Accessed August 17, 2026. https://www.businesswire.com/news/home/20260720458854/en/Acadia-Pharmaceuticals-Receives-FDA-Fast-Track-Designation-for-Remlifanserin-in-Alzheimers-Disease-Psychosis
2. Acadia Pharmaceuticals initiates phase 2 clinical trial of ACP-204 for the treatment of Alzheimer’s disease psychosis. News release. Acadia Pharmaceuticals. November 27, 2023. Accessed November 29, 2023. https://acadia.com/media/news-releases/acadia-pharmaceuticals-initiates-phase-2-clinical-trial-of-acp-204-for-the-treatment-of-alzheimers-disease-psychosis/