Acadia falls 10% after its Alzheimer's psychosis drug misses its main goal; Phase 3 goes ahead at one dose

Acadia Pharmaceuticals shares fell about 10% on Thursday after the company said its experimental drug remlifanserin narrowly missed the main goal of a Phase 2 study in Alzheimer's disease psychosis. The stock was at $22.92 shortly before 3 p.m. Eastern, down $2.51 from Wednesday's close of $25.43, according to Nasdaq data. About 4.3 million shares had traded, against a daily average of about 1.6 million.

What the trial showed

According to Acadia's release, published on Business Wire:

• Primary endpoint missed. On the hallucinations and delusions scale (SAPS-H+D), the 60 mg dose improved scores by 12.6 points after six weeks, against 10.4 points on placebo. The gap of 2.2 points gave a standardized effect size of 0.26 and a p-value of 0.0603, just above the usual 0.05 bar.
• Key secondary endpoint hit, nominally. On a clinician's overall severity rating, the 60 mg dose improved 1.3 points versus 0.9 for placebo, an effect size of 0.37 with p=0.0077. Acadia labels that result "nominal", because once the primary endpoint misses, secondary results do not count as formal proof.
• The lower dose did little. The 30 mg dose "showed minimal improvement across endpoints compared to placebo," the company said, and it will be dropped from the Phase 3 program.
• Safety looked clean. Adverse event and dropout rates were similar to placebo, with no signal of heart-rhythm (QT) prolongation and no deaths in the drug arms.

Acadia said it will keep enrolling its two Phase 3 studies, amend them to remove the 30 mg arm, and present full results at the Clinical Trials on Alzheimer's Disease conference in Boston on Nov. 16-19.

The thing the headline gets wrong

"Narrowly missed" is accurate, and a p-value of 0.06 in a mid-stage study is not the same as a drug that does nothing. The stronger signal against the program is the dose response. A dose that barely beats placebo tells investors the useful range is narrow, and Phase 3 now rests on the single 60 mg arm, with an effect size on the main scale that Acadia itself puts at 0.26. That leaves less room for error in a larger trial.

It also matters how the company framed this readout beforehand. In its second-quarter release on Aug. 4, chief executive Catherine Owen Adams called remlifanserin "a potentially transformational opportunity for Acadia." There is no approved drug for Alzheimer's disease psychosis, which is why expectations were high.

The number behind the number: what is left in the stock

Acadia is not a one-drug biotech. Its two approved products, Nuplazid for Parkinson's disease psychosis and Daybue for Rett syndrome, brought in $308 million of revenue in the second quarter, up 16% from a year earlier, and the company raised full-year revenue guidance to $1.24 billion to $1.30 billion. It reported net income of $32 million for the quarter and held $956 million in cash and investments at June 30.

Nasdaq put Acadia's market value at about $3.95 billion at Thursday's price. Our arithmetic from those figures:

• That implies about 172 million shares, so Thursday's drop removed roughly $430 million of market value.
• The company now trades at about 3.1 times the midpoint of its 2026 revenue guidance.
• Cash and investments are about a quarter of the market value.
• Nuplazid was $183 million of the $308 million in quarterly revenue, about 59%. Remlifanserin, like Nuplazid, targets the 5-HT2A receptor, so this study was also a test of whether Acadia could carry that science into a much larger patient group.

What traders are watching now is the full dataset in November, particularly whether the 60 mg effect was still widening at week six, as Acadia says it was, and any change to the Phase 3 size or timeline. Investing.com reported that Goldman Sachs reiterated its Sell rating after the miss.

Sources: Acadia Pharmaceuticals (Business Wire releases of Sept. 24 and Aug. 4, 2026); Nasdaq; Investing.com. Market value, share count and ratios are our own calculations from Nasdaq data. This is market information, not investment advice.