Chelsea Therapeutics Inc said its experimental hypotension drug met the main goal of a study by significantly reducing dizziness in patients at week one, but results beyond that period were not statistically significant.
The U.S. Food and Drug Administration declined to approve the drug, Northera, in March, and asked for data that proved it was effective over two to three months.
The company's shares, which have lost about two-thirds of its value so far this year, fell 22 percent to $1.40 in extended trading after closing at $1.79 on Tuesday on the Nasdaq.
Chelsea said in August that it would modify the main goal of the ongoing 306B study, though the FDA had said the study was unlikely to provide sufficient data for a marketing application and had suggested the company conduct an additional trial.
The drugmaker said on Tuesday that preliminary data showed that beyond week one, dizziness/lightheadedness and standing blood pressure predominantly favored Northera-treated patients over placebo, although the results were not statistically significant.
The drug, known generically as droxidopa, is designed to treat symptomatic neurogenic orthostatic hypotension -- a chronic and often debilitating drop in blood pressure on standing up that is most often associated with Parkinson's disease.
(Reporting by Vidya P L Nathan in Bangalore; Editing by Anthony Kurian)