WASHINGTON, Oct 17 (Reuters) - Company data for a mass-produced version of Genzyme Corp's (GENZ.O: Quote, Profile, Research, Stock Buzz) Myozyme to treat Pompe disease raises questions over how well it works and whether more data is needed before approval, U.S. regulatory staff said in documents released on Friday.
While side effects appear similar to the smaller-scale version already available, long-term exposure was not adequately studied, U.S. Food and Drug Administration reviewers wrote.
There was also not enough data to show the drug for the rare enzyme disorder worked in children, and agency officials should consider limiting approval for adult-use only, they added.
While the currently-approved Myozyme is approved for children with Pompe disease, "concerns regarding the potency ... and the lack of data regarding efficacy" strongly suggest the newer version should not be approved for such young patients, the staff wrote.
The documents were released ahead of an FDA advisory panel on Tuesday to discuss whether to approve large-scale production of the drug.
The FDA has already approved a version of Myozyme manufactured at a Genzyme facility that uses a 160-liter bioreactor. But Genzyme is seeking U.S. clearance to make the drug, known chemically as algucosidase alfa, at a 2,000-liter plant.
The agency has said it considers the version made at the larger facility to be a different product from that made at the smaller plant because of differences in carbohydrate structure, thus requiring a separate review.
SIDE EFFECTS
In a study comparing the new version to a placebo, patients experienced side effects similar to the currently available version, including severe reactions and urinary trouble, the FDA said.
FDA statisticians also had concerns about Genzyme's application, calling it "unusual in several ways" and noting that the company changed its goals for the drug in the middle of a clinical study.
Still, they added the fact that the disease is rare should be taken into consideration.
According to the company, roughly between 5,000 and 10,000 people worldwide have the condition, in which the lack of a certain enzyme causes the heart and other muscles to fail. The condition is inherited and can cause death.
In separate documents released on Friday, Genzyme said approval for the 2,000-liter version was critical for it to expand capacity and make its drug more widely available. Its experience with the other version as well as clinical trial data show the new version is safe and effective, it said.
On Tuesday, the FDA will seek a recommendation from its panel of outside experts on whether to approve the new version. A final FDA decision is expected by Nov. 29.
Some analysts said the FDA staff's concerns appeared negative and raised doubts about Genzyme's ability to win FDA approval any time soon.
"We are surprised that efficacy has been brought into question. ... Overall, we think this panel will not be the 'walk in the park' many investors (and the company) had suggested," JP Morgan analysts wrote in a research note.
Others said the drug was likely to win approval eventually, although maybe not this year.
"Genzyme has a history of stumbling in the final stages of regulatory processes but ultimately securing approval," Bernstein Research analyst Geoffrey Porges said in a separate note.
Shares of Genzyme were down 32 cents at $65.46 in midday trading on the Nasdaq after earlier falling more than 1.2 percent.
The documents were released on the FDA's website here
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