Acadia pushes Alzheimer's psychosis drug to phase 3 despite missed trial goal

Overview

Updated 2 hours ago

Acadia Pharmaceuticals said its experimental Alzheimer's psychosis treatment missed the primary goal of a phase 2 trial. The company is advancing remlifanserin to phase 3 anyway, betting a refined study design can turn a near-miss into a win.

Alzheimer's disease psychosis, marked by hallucinations and delusions, affects about 30% of Alzheimer's patients. No drug is approved for it. Acadia sees a potential $4 billion market if remlifanserin succeeds.

Why it matters

If remlifanserin clears phase 3, it would be the first approved treatment for Alzheimer's psychosis, a condition affecting roughly a third of Alzheimer's patients.

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Key Indicators

0.26

Primary endpoint effect size

Change on SAPS-H+D at week 6, 60mg remlifanserin vs placebo; p=0.0603, just above the significance threshold.

0.37

Key secondary endpoint effect size

Change on the CGI-S-ADP severity measure, with nominal statistical significance (p=0.0077).

0.33

Phase 2 effect size with refined enrollment criteria

Company analysis raising the baseline psychosis threshold improves the primary effect size to 0.33.

30%

Alzheimer's patients with psychosis

Share of Alzheimer's patients experiencing hallucinations or delusions, per Acadia.

$4B

Peak sales potential

Acadia's estimate across Alzheimer's disease psychosis and Lewy body dementia psychosis.

Voices

Curated perspectives — historical figures and your fellow readers.

Ever wondered what historical figures would say about today's headlines?

People Involved

Catherine Owen Adams

Chief Executive Officer, Acadia Pharmaceuticals

Advancing remlifanserin to phase 3

Elizabeth H. Z. Thompson, Ph.D.

Executive Vice President and Head of Research and Development, Acadia Pharmaceuticals

Designing phase 3 protocol amendments

Evan Seigerman

Senior Analyst, BMO Capital Markets

Monitoring Acadia's phase 3 plans

Organizations Involved

Acadia Pharmaceuticals

Biopharmaceutical company

Developer of remlifanserin; planning phase 3 amendments

San Diego-based biopharmaceutical company developing remlifanserin for Alzheimer's disease psychosis.

BMO Capital Markets

Investment bank

Provider of analyst commentary on Acadia

Capital markets firm whose analysts cover Acadia and called the phase 2 result a 'near miss.'

TD Cowen

Investment bank

Provider of analyst expectations and bear-case estimate

Analysts expected a phase 2 effect size of 0.35 to 0.4 and cut their phase 3 success probability to 25% after the miss.

Timeline

April 2016 September 2026

2 events Latest: Today

September 2026
Phase 2 RADIANT results miss primary endpoint
Today Clinical trial

Remlifanserin 60mg missed the primary endpoint (p=0.0603) but hit the key secondary severity measure. Acadia plans phase 3 amendments removing the 30mg arm.
Today
April 2016
FDA approves Nuplazid for Parkinson's psychosis
Regulatory

Acadia's pimavanserin became the first drug approved for psychosis in a neurodegenerative disease. Its QT prolongation risk drove the remlifanserin follow-up.
April 29th, 2016

Scenarios

Phase 3 meets primary endpoint, remlifanserin heads to FDA

Likely Resolves by End of 2028

Discussed by: Acadia management, BMO Capital Markets analyst Evan Seigerman

Acadia amends its two ongoing phase 3 trials to use only the 60mg dose and enrich enrollment for patients with modestly higher baseline psychosis. The company says this reanalysis lifts the effect size to 0.33 on the primary measure and 0.43 on the severity measure. If the phase 3 trials hit their endpoints, remlifanserin would become the first approved treatment for Alzheimer's disease psychosis.

Phase 3 also misses, remlifanserin abandoned

Possible Resolves by End of 2028

Discussed by: TD Cowen (cut phase 3 success probability to 25%), persistent market skepticism

The 0.26 effect size fell below TD Cowen's 0.35-0.4 expectation, and the p-value of 0.0603 left no margin for error. If the enriched enrollment criteria do not translate into stronger drug-placebo separation, the phase 3 trials could miss as well. Acadia would then absorb the development cost and rely on revenue from Nuplazid and Daybue.

FDA seeks additional data despite a positive phase 3

Uncertain Resolves by End of 2029

Discussed by: BMO analysts (noting phase 3 'could still produce a significant improvement'), regulatory precedent

If phase 3 shows statistical significance but a modest effect size, the FDA could request an additional confirmatory trial or impose a narrow label. The enrichment strategy, which targets sicker patients, also raises questions about generalizability to the broader Alzheimer's psychosis population. Either outcome would push any approval well past 2029.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

April 2016

Nuplazid (pimavanserin) approval (April 2016)

The FDA approved Acadia's Nuplazid for Parkinson's disease psychosis, the first drug ever cleared for a dementia-related psychosis. Pimavanserin works by blocking the 5HT2A receptor, but carries a QT prolongation warning, a cardiac rhythm risk.

Then

Nuplazid became a commercial product and validated the 5HT2A mechanism for psychosis in neurodegenerative disease.

Now

The QT liability limited its use and pushed Acadia to develop remlifanserin, a follow-on designed to keep the efficacy while reducing the cardiac risk.

Why this matters now

Remlifanserin targets the same receptor as Nuplazid; the phase 2 result showed no QT signal, a key improvement over its predecessor.

May 2023

Rexulti (brexpiprazole) for Alzheimer's agitation (May 2023)

The FDA approved Otsuka and Lundbeck's Rexulti for agitation in Alzheimer's disease, the first approved treatment for a neuropsychiatric symptom of the disease. Approval followed mixed trial results and extensive regulatory review.

Then

Rexulti's approval gave physicians a labeled option for Alzheimer's agitation, which had been managed with off-label antipsychotics.

Now

It established that the FDA will clear drugs for Alzheimer's behavioral symptoms when the evidence of benefit is sufficient.

Why this matters now

Rexulti opened a regulatory path for treating Alzheimer's neuropsychiatric symptoms. Remlifanserin targets psychosis, a distinct symptom with no approved options at all.

Early 2000s

Off-label antipsychotics for Alzheimer's psychosis (2000s)

For years, physicians treated Alzheimer's psychosis with antipsychotics like risperidone and olanzapine, despite FDA black-box warnings about increased mortality in elderly dementia patients. These drugs also worsen motor function, a serious risk in a population prone to falls.

Then

The black-box warnings reduced use but left Alzheimer's psychosis without a safe, approved treatment.

Now

The experience created demand for a drug with a motor-safe profile, a gap Acadia aims to fill.

Why this matters now

The phase 2 data showed remlifanserin does not worsen motor symptoms or cognition, a critical advantage over the off-label antipsychotics still used for this condition.