WASHINGTON A Schering-Plow Corp SGP.N drug to reverse the effects of anesthesia appears to be generally safe, U.S. regulatory staff said, but they questioned how the company defined effectiveness in a key study.
Regulators are also awaiting data on a rare occurrence of allergic reactions in some patients using the drug, to be called Bridion, Food and Drug Administration staffers wrote in documents posted on the FDA's Web site on Friday.
The FDA staff said: "The Applicant appears to have made a thorough assessment of the safety of Bridion in a relatively healthy adult population and with the possible exception of hypersensitivity, found the drug product to be safe" compared with current agents.
Schering-Plow shares were down 31 cents or 1.6 percent to $19.72 in afternoon trading on the New York Stock Exchange.
Chief executive Fred Hassan has said the drug could be a growth driver going forward and some analysts have said that, if approved, it could generate up to $1 billion a year in revenue.
"Expectations for this drug are quite high so any concern raised is appropriately making people nervous," said Barbara Ryan, an analyst at Deutsche Bank. But she expects the panel to see that the benefits outweigh the risks.
The review comes ahead of an advisory panel meeting next week to consider the risks and benefits of the drug, known generically as sugammadex. The FDA typically takes the advice of its panels.
The drug seeks to reverse the muscular blocking effects of muscle relaxants, to help patients recover more quickly from anesthesia after medical procedures.
In a question for the panel to consider, the FDA staff asked whether the study goal aimed at proving efficacy has "clinical relevance," especially in emergency room situations.
The company says its data show the drug helps patients come out of anesthesia at least 10 times faster than current regimes, helping them recover more quickly.
The most common side effects associated with the drug are pain and nausea, with rare cases of allergic reactions, according to the company.
Of these reactions, the FDA staff wrote: "The occurrence of this reaction, even in a relatively small number of subjects, could have a significant impact on the overall finding of safety if it is found to be related to Bridion."
The FDA is waiting for a 120-day safety update from the company.
Schering-Plough, in a separate set of documents, said allergic or hypersensitivity reactions occurred at a "very low" frequency of less than 1 percent in the group getting the drug.
It also said none of those reactions "were judged by the investigator to be related to trial medication."
In addition, in studies in young animals, the drug bound to bone and teeth, which FDA staff called a "concern."
The company acknowledged that finding, but said studies in rats found it does not affect tooth color or bone quality, structure or development.
Schering-Plow acquired the drug in its $14 billion acquisition of Akzo Nobel NV's (AKZO.AS) drug unit Organon.
(Reporting by Kim Dixon, editing by Andre Grenon and Gerald E. McCormick)
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