Acadia Pharmaceuticals (ACAD) - Get Report needed to find a way to justify moving Nuplazid into a late-stage clinical trial of Alzheimer's disease psychosis, so the company designed a phase II clinical trial with shifting endpoints and an efficacy threshold so low that basically any drug activity at all, no matter how meaningless or fleeting, could be deemed a success.

Mission accomplished, with a healthy dose of skepticism.

On Tuesday, Acadia said Alzheimer's patients treated with Nuplazid for six weeks had fewer hallucinations and delusions than comparable patients treated with a placebo. Based on the NPI-NH Psychosis score, Nuplazid tracked a 1.8-point improvement over placebo at 6 weeks -- a benefit that is on the margins of both clinical and statistical significance.

Regardless, Acadia claimed victory. Nuplazid, approved last year for Parkinson's disease psychosis, will now be pushed ahead into a phase III study of Alzheimer's disease psychosis.

That decision seemed predetermined. Acadia conceded Tuesday that the antipsychotic effect of Nuplazid seen at six weeks disappeared at 12 weeks, relative to placebo. The drug's effect is small and doesn't last long.

Acadia claims the study was always designed to measure primary efficacy at six weeks, but the company's own description of the phase II study listed on ClinicalTrials.gov says the psychosis efficacy endpoint was to be measured at 12 weeks. On that basis, the study actually failed.

Acadia offered no explanation for the discrepancy in the way the Nuplazid phase II study was described.

On another measure of disease severity, the Clinical Global Impression Scale, Nuplazid showed no improvement compared to placebo.

The main side effects of Nuplazid observed in the phase II study were falls and agitation, which could present problems for Alzheimer's patients, particularly for people living at home and cared for by a family member. The phase II study only enrolled Alzheimer's patients living in a nursing home.

Acadia shares rose 12% to $28.44 in early Tuesday trading. During pre-market trading, Acadia shares were up almost 50%, so the stock has retreated as doubts about the Nuplazid data take hold.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.