San Diego, California, USA | July 21, 2026
Acadia Pharmaceuticals announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to remlifanserin (ACP-204) for the treatment of hallucinations and delusions associated with Alzheimer’s disease psychosis (ADP). The designation recognizes the significant unmet medical need for new therapies, as there are currently no FDA-approved treatments specifically indicated for Alzheimer’s disease psychosis. FDA Fast Track status is intended to accelerate the development and regulatory review of investigational medicines that address serious conditions and have the potential to provide meaningful clinical benefits. Alongside the regulatory milestone, Acadia confirmed that enrollment in the Phase 2 portion of its RADIANT clinical program has been completed, with topline results expected between September and October 2026, while Phase 3 screening and patient enrollment are already underway through the study’s seamless development design.
Remlifanserin Offers a Novel Non-Dopaminergic Approach to Alzheimer’s Psychosis
Remlifanserin is an investigational, highly selective 5-HT2A receptor inverse agonist designed to reduce hallucinations and delusions associated with Alzheimer’s disease psychosis through a mechanism that differs from conventional antipsychotic therapies. By selectively targeting the serotonin 5-HT2A receptor, the therapy is believed to restore the brain’s excitatory and inhibitory (E/I) balance without directly blocking dopamine D2 receptors, potentially avoiding many of the safety and tolerability concerns commonly associated with atypical antipsychotic medications. This differentiated mechanism positions remlifanserin as a promising candidate for treating psychosis in patients with Alzheimer’s disease and Lewy body dementia, where treatment options remain extremely limited and the need for safer therapies continues to grow.
RADIANT Clinical Program Progresses Toward Late-Stage Development
The RADIANT clinical development program is evaluating the efficacy and safety of remlifanserin in patients experiencing hallucinations and delusions caused by Alzheimer’s disease psychosis. With Phase 2 enrollment now complete, Acadia expects to deliver topline efficacy and safety data during September to October 2026, providing a key milestone for the program. The study has been designed with an operationally seamless transition into Phase 3, enabling patient screening and enrollment for the pivotal studies to begin before completion of the Phase 2 data analysis. This streamlined development strategy is intended to shorten overall development timelines while maintaining rigorous clinical evaluation, potentially accelerating the availability of a much-needed treatment option for patients and caregivers affected by this debilitating neurological condition.
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FDA Fast Track Reinforces Acadia’s Neuroscience Development Strategy
According to Catherine Owen Adams, Chief Executive Officer of Acadia Pharmaceuticals, the FDA’s Fast Track designation highlights both the seriousness of Alzheimer’s disease psychosis and the urgent need for innovative therapies capable of improving patient outcomes. The company views the designation as an important validation of the remlifanserin development program and remains focused on advancing the therapy through late-stage clinical development as rapidly as possible. Acadia has established a strong presence in central nervous system disorders, with an existing commercial portfolio that includes the first and only FDA-approved treatments for Parkinson’s disease psychosis and Rett syndrome, while continuing to expand its pipeline across Alzheimer’s disease psychosis, Lewy body dementia psychosis, and other neurological disorders. With FDA Fast Track designation, advancing Phase 2 and Phase 3 development, and a novel serotonin-based mechanism of action, remlifanserin has the potential to become the first FDA-approved therapy specifically indicated for Alzheimer’s disease psychosis, addressing one of the most significant unmet needs in neuropsychiatric medicine.
Source: Acadia Pharmaceuticals press release
