(Reuters) - Acorda Therapeutics Inc said on Monday that a low-dose version of its multiple sclerosis drug Ampyra did not work in a clinical study, a potentially positive result that will hold generic competition at bay until 2027.
A post-marketing study of Ampyra failed to show an improvement in patients' walking speed when 5 mg of the drug was given twice a day. Had the 5 mg version worked, generic rivals could have entered the market in 2017 or 2018.
A 10 mg version of the drug was approved by the U.S. Food and Drug Administration in 2010, and that dose has patent protection until 2027. The agency had asked the company to conduct a study of a 5 mg dose.
On a less positive note, the latest trial showed that the approved 10 mg dose also failed to improve walking speeds when compared with a placebo.
The company said the trial was designed differently from those on which the initial approval was based. Still, it raises some uncertainty about the drug's prospects.
"What the FDA ultimately does with the new data (is) unclear," said Mark Schoenebaum, an analyst at ISI Group. "One option -- which we think is most likely -- is to simply include the data in the label and allow physicians to prescribe as they see fit."
Schoenebaum said he doubts the new data will have a major impact on sales, since physician perceptions about efficacy are built around the original trials, though there might be a "modest drag."
In a worst case scenario, the FDA could convene an advisory panel to discuss the new data, he said.
On a conference call with analysts, Acorda CEO Ron Cohen said he did not expect the latest data to be included in Ampyra's label.
Acorda chief scientific officer, Andrew Blight said the lack of statistically significant results may be due to the prolonged and complex nature of patient visits where patients had to wait for 3 to 4 hours for a second evaluation.
"This is unlike previous studies where patients generally came to a single evaluation and this extra burden may have introduced significant additional variability," Blight said during the conference call.
Jeff Macdonald, a spokesman for Acorda, said the company believes the totality of the data it collected shows that the 10 mg dose is effective.
"In addition to this trial, the drug has been on the market for two years, and more than 55,000 patients have used it," he said.
In the latest trial, two patients, each from the 5 mg and 10 mg treatment group, experienced serious adverse events, including the loss of consciousness in the 10 mg group, Acorda said in a statement.
In July, the FDA issued a warning to patients and physicians about the increased risk of seizures from the drug in multiple sclerosis patients with kidney impairment.
Multiple sclerosis is a chronic, often disabling disease that attacks the central nervous system and can lead to numbness, paralysis and a loss of vision.
Ampyra had sales of $66.3 million in the quarter ended June.
Acorda's marketing partner Biogen Idec Inc, which aims to sell Ampyra under the brand name Fampyra in Europe, received conditional approval for the drug in Europe in July last year.
Conditional approval is granted to drugs in which the benefit is seen to outweigh the risk but where additional information is needed to confirm that view.
Shares of the Ardsley, New York-based company were trading up 3.6 percent at $22.52 when markets opened on Monday.
(Reporting By Pallavi Ail in Bangalore and Toni Clarke in Boston, editing by Sreejiraj Eluvangal and Jeffrey Benkoe)