Shares of Neuro-Hitech Inc. plunged nearly 70 percent after the firm reported disappointing top-line results of its Phase II trial of Huperzine A in Alzheimer's patients.

Results from the 210-patient study in mild to moderate Alzheimer's disease (AD) showed no statistical difference in the primary endpoint, defined as the mean change over placebo in patients getting 200 mcg of Huperzine A twice-daily as measured by the AD Assessment Scale - Cognitive (ADAS-Cog) scores after 16 weeks of treatment. The company reported, however, that a higher dose - Huperzine A 400 mcg twice-daily - showed cognitive enhancement on ADAS-Cog compared to placebo, and Neuro-Hitech CEO Gary T. Shearman said in a press release those higher-dose data were "encouraging."

Even so, the Phase II failure didn't sit well with investors. Neuro-Hitech's stock (NASDAQ:NHPI) lost $1.99, or 68 percent, Friday to close at 93 cents.

Additional data from the study showed that the maximum cognitive improvement was observed at week 11 of treatment. Over 16 weeks, Huperzine A (400 mcg) improved cognition over placebo, and the company reported a trend to cognitive improvement over placebo at week 16.

Neuro-Hitech said there was an unexpected improvement in cognition in the placebo group at week 16 vs. baseline.

Data from other secondary endpoints, including clinical global impression of change and the Neuropsychiatric Inventory, showed no statistical difference between placebo and either dosages of Huperzine A after four months of treatment, though there was an trend to improvement on activities of daily living with the highest dose.

New York-based Neuro-Hitech said it plans to review the data and anticipates exploring the drug's effect in further studies.

Huperzine A is a naturally occurring alkaloid compound derived from the club moss Huperzia serrata and is designed to work as a reverse inhibitor of acetylcholinesterase.