* Ampyra first drug cleared to boost walking speeds in MS
* Company says drug should be available in March
* Acorda shares jump nearly 10 pct (Adds company, analyst, FDA comments; updates shares)
WASHINGTON, Jan 22 (Reuters) - Acorda Therapeutics Incwon U.S. approval on Friday for the first drug to improve walking ability in patients with multiple sclerosis.
MS patients in clinical trials who took the oral drug, Ampyra, had faster walking speeds than others who got a placebo, the Food and Drug Administration said in a statement.
Acorda shares jumped 9.8 percent to close at $28.12 on the Nasdaq. Shares of Elan Corp, which will manufacture the drug, rose 2.3 percent to $8.04 on the New York Stock Exchange.
Acorda Chief Executive Ron Cohen said he expected the drug will be available in March. He said the company has not yet disclosed a price, and he declined to give sales projections.
Mike King, analyst for Merriman Curhan Ford & Co, estimates Ampyra will have worldwide sales of $1 billion by 2015 or 2016.
There is no cure for multiple sclerosis, a chronic disease affecting about 400,000 Americans and 2.5 million people worldwide. It attacks the central nervous system and can cause numbness or paralysis of arms and legs. Walking ability tends to worsen over time and patients may require wheelchairs.
"Trouble with walking is one of the most debilitating problems people with MS face," Dr. Russell Katz, head of the FDA division that reviewed Ampyra, said in a statement.
Acorda conducted two major studies of the drug, measuring how fast more than 500 patients given either Ampyra or a placebo could walk a distance of 25 feet (8 meters).
In the first study, about 35 percent of patients responded to the drug versus 8 percent who took a placebo. For the second study, response rates were 43 percent for the drug and 9 percent for a placebo.
FDA reviewers had told an advisory panel in October the difference in walking speed with either group was very small. But company representatives said the drug's ability to shave a few seconds off the walking test could add up over the course of an hour and help with simple tasks such as getting to the bathroom quickly.
The panel backed the drug, saying Acorda's data showed it was safe and effective.
In Friday's announcement, the FDA said Ampyra can cause seizures if patients take higher-than-recommended doses, and it should not be used by patients with moderate to severe kidney disease. The recommended dose is two 10-milligram tablets per day.
FDA spokeswoman Sandy Walsh said the drug did not include a boxed warning, the strongest type of warning for prescription drugs. Some industry analysts had expected a boxed warning.
The drug's generic name is dalfampridine. (Reporting by Lisa Richwine and Bill Berkrot, Editing by Robert MacMillan and Matthew Lewis)
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