Impax Laboratories Falls as FDA Rejects Parkinson’s Drug

Impax Laboratories Inc. (IPXL) fell the most in more than two months after the company failed to win U.S. approval for an extended-release formulation of a Parkinsons disease drug used to relieve spasms in patients.

Impax tumbled 7.7 percent to $19.40 at 12:18 p.m. New York time, after dropping as low as $18.90 for its largest intraday decline since Oct. 31. Shares of the Hayward, California-based company increased 4.9 percent in the 12 months ended Jan. 18.

The Food and Drug Administration requires a re-inspection of a plant involved in the development of the medicine called Rytary, which combines standard Parkinsons medications in a new sustained release formulation, Impax said yesterday in a statement. A warning letter was issued in May 2011, Impax said.

We will work with the FDA on the appropriate next steps for the Rytary application, Impax President and CEO Larry Hsu said in the statement. We remain committed to resolving the warning letter and bringing this new treatment option to patients who are suffering from Parkinsons disease.

The medication would likely be used most among patients for whom the standard medicines, levodopa and carbidopa, have stopped working as reliably, said David Amsellem, an analyst with Piper Jaffray & Co. in New York. Rytary could generate peak sales of $200 million to $300 million, Amsellem said.

A controlled-release product is something that has been elusive over the years, Amsellem said in a telephone interview.

Impax will develop and sell Rytary in the U.S. and Taiwan while GlaxoSmithKline Plc (GSK), based in London, will market it in other regions throughout the world. Impax already markets a generic version of a longer-acting combination called Sinemet, sold by Merck & Co. (MRK)

Mercks Sinemet extended-release carbidopa-levodopa tablet received approval in 1991 though its not widely used, Amsellem said. People who use it are more likely to suffer impairment of voluntary movement than those who use the immediate-release version, according to the label for the medication.

Patients with advanced Parkinsons disease who used Rytary experienced a 34 percent decrease in the amount of time during waking hours when the medication wore off and involuntary muscle movements returned, the companies said in an August 2011 statement. This was compared with a decrease of 10 percent for those who used the immediate-release generic drugs combined with entacapone, a medicine that helps more of the other treatments reach the brain.

The starting point was 5.9 hours, improving to 3.8 hours of off time when Rytary wore off compared with 5.2 hours for the generics.

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Impax Laboratories Falls as FDA Rejects Parkinson’s Drug