Acadia Pharmaceuticals Announces Phase 3 Enabling Topline Results from Phase 2 RADIANT Study of Remlifanserin for the Treatment of Alzheimer’s Disease Psychosis (ADP)

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— Meaningful and consistent efficacy trends across endpoints support continuing with Phase 3 development of 60 mg once daily remlifanserin in ADP, with demonstrated evidence of dose effect

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— Narrowly missed primary endpoint of SAPS H+D (p=0.0603) with significance (nominal) on key secondary endpoint of CGI-S-ADP (p=0.0077)

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— Favorable safety and tolerability profile across both doses

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— Detailed results to be presented at upcoming Clinical Trials on Alzheimer’s Disease (CTAD) conference in November

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— Conference call and webcast to be held today at 8:00 a.m. Eastern Time

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SAN DIEGO — Acadia Pharmaceuticals Inc. (Nasdaq: ACAD) today announced Phase 3 enabling topline results from the Phase 2 portion of the ongoing RADIANT clinical trial program evaluating remlifanserin for the treatment of hallucinations and delusions associated with Alzheimer’s disease psychosis (ADP).

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For the primary endpoint of change from baseline in the Scale for the Assessment of Positive Symptoms-Hallucinations and Delusions subscales (SAPS-H+D), once daily 60 mg remlifanserin demonstrated a change of -12.6 versus a -10.4 change for placebo at week 6, yielding a standardized effect size of 0.26 (p=0.0603). For the key secondary endpoint, Clinical Global Impression – Severity (CGI-S-ADP), the 60 mg dose achieved a change from baseline of -1.3 versus a change of -0.9 for placebo at week 6, yielding a standardized effect size of 0.37 [p=0.0077 (nominal)]. On both efficacy measures, the difference in the 60 mg dose versus placebo increased through the 6-week treatment period. The 30 mg dose showed minimal improvement across endpoints compared to placebo. All analyses were performed in the pre-specified modified full analysis set (mFAS¹) population.

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In this study, across both doses, remlifanserin demonstrated a favorable safety profile, with rates of adverse events, serious adverse events, and discontinuations due to adverse events, similar to placebo. There was no signal of QT prolongation versus placebo. This dataset suggests no negative impact on motor symptoms or cognition. Additionally, there were no deaths in the remlifanserin treatment arms.

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Given these data, Acadia plans to continue enrolling its two ongoing Phase 3 studies evaluating remlifanserin in ADP while implementing amendments to the Phase 3 program, including removing the 30 mg dosage arm.

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“We are pleased that the Phase 2 RADIANT data support continuation of the Phase 3 ADP program, with new insights helping us to refine the program for future regulatory success. These results provide valuable information regarding the efficacy, safety and tolerability of once daily remlifanserin in Alzheimer’s disease psychosis,” said Catherine Owen Adams, Chief Executive Officer of Acadia Pharmaceuticals. “We are excited about the potential of remlifanserin in this area of high unmet need, for which there are no currently approved therapies.”

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“The Phase 2 RADIANT findings provide encouraging evidence that 60 mg once daily remlifanserin may have the potential to reduce hallucinations and delusions in patients with Alzheimer’s disease,” said Jeffrey Cummings, M.D., Sc.D., Director of the Chambers-Grundy Center for Transformative Neuroscience, University of Nevada, Las Vegas. “This patient population has a significant need for an efficacious medication that is well tolerated, convenient to administer, and is compatible with the many concomitant medications commonly used by patients with Alzheimer’s disease. In particular, avoiding negative impacts on motor symptoms and cognition is encouraging, and such a medicine could be an important treatment option for patients.”

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Acadia plans to present detailed safety and efficacy results from the RADIANT Phase 2 study in an oral presentation at the upcoming Clinical Trials on Alzheimer’s Disease (CTAD) conference, taking place November 16-19, 2026 in Boston.

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Additionally, remlifanserin is currently being investigated in an additional Phase 2 study to evaluate its efficacy, safety and tolerability for the treatment of Lewy body dementia psychosis.

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Conference Call and Webcast Information

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Acadia will discuss top-line results from its Phase 2 RADIANT study of remlifanserin for the treatment of Alzheimer’s disease psychosis via conference call and webcast today at 8:00 a.m. Eastern Time. The conference call webcast is available at this registration link and will be available on Acadia’s website, acadia.com under the investors section and will be archived there for at least 90 days following the event.

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About RADIANT

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RADIANT is a global, multi-center, randomized, double-blind, placebo-controlled, operationally seamless Phase 2 and 3 clinical trial program evaluating remlifanserin for the treatment of hallucinations and delusions associated with Alzheimer’s disease psychosis (ADP). The Phase 2 portion of the program was designed to evaluate the efficacy, safety, and tolerability of remlifanserin at 60 mg and 30 mg once-daily doses compared with placebo. Patients who complete the study will have the option of participating in a long-term open-label extension (OLE) study.

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About Alzheimer’s Disease Psychosis

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According to the Alzheimer’s Association, more than 7 million people in the United States are living with Alzheimer’s disease (AD).^2,3 Approximately 30% of patients with AD experience psychosis, commonly consisting of hallucinations and delusions.⁴ These symptoms may be frequent and severe and may recur over time.⁵ A hallucination is defined as a perception-like experience that occurs without an external stimulus and is sensory (seen, heard, felt, tasted, sensed, smelled) in nature. A delusion is defined as a false, fixed belief despite evidence to the contrary. Serious consequences have been associated with psychosis in patients with dementia, such as increased likelihood of nursing home placement, more severe dementia, and increased risk of morbidity and mortality.^6,7 There is no FDA-approved drug for the treatment of Alzheimer’s disease psychosis.