UPDATE 2-US FDA questions Genzyme knee pain treatment study

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By Susan Heavey

WASHINGTON Dec 5 (Reuters) - A study of Genzyme Corp's GENZ.O latest version of its injectable knee pain treatment may be inadequate to weigh how well the product works, U.S. regulatory reviewers said in an analysis released on Friday.

The study showed a "statistically significant" reduction of pain in patients given the treatment, called Synvisc-One, but staff of the Food and Drug Administration raised questions about its small sample size.

Synvisc-One is a new, single-dose formulation of the company's Synvisc injection that aims to provide up to six months of pain relief from osteoarthritis of the knee. The older Synvisc is given via three injections, each one week apart.

An FDA advisory panel meets Tuesday to discuss whether the new version should be approved. The FDA will weigh the panel's advice when making its final decision, expected by Dec. 23.

The FDA staff is concerned that Genzyme conducted its study in Europe so its procedures were not reviewed by the agency, the analysis said.

Additionally, the study followed patients for only 26 weeks but effects of the similar injections have been known to last as long as a year, the staff wrote.

The FDA staff did say the drug appears as safe as the older version. "The materials used to manufacture the Synvisc-One ... are equivalent to the components used in the manufacture of the currently marketed Synvisc product, and is considered to be safe," they wrote.

Shares of Genzyme rose 4.6 percent to $64.04 in afternoon trading on the Nasdaq.

Analysts said the FDA's panel of advisers is likely to offer lukewarm support but ultimately back the product.

"While we expect the Committee ultimately to recommend an approval, we wouldn't expect a ringing endorsement," J.P. Morgan analyst Geoff Meacham wrote in a research note.

Sales of the treatment are also expected to be modest, Meacham and other analysts said.

"While we don't see these documents as particularly comforting for Synvisc-One, we point out that Synvisc is a minor revenue contributor," Robert W. Baird & Co. analyst Christopher Raymond said.

Still, others said the FDA could delay its decision and ask for more data, especially since it provides no new pain benefits for patients. The FDA already requested additional analyses and data on Synvisc-One in late 2007.

Synvisc has been used to treat more than 5 million knees in the United States since its approval in 1997, Genzyme said. It is approved for patients who do not respond to conservative non-drug therapy and simple analgesics such as acetaminophen.

Genzyme, in separate documents also released on Friday, said its "study confirms a favorable risk/benefit profile."

The documents were posted to the FDA's website here (Reporting by Susan Heavey and Lisa Richwine; Editing by Gerald E. McCormick, Derek Caney and Matthew Lewis)