FDA Skeptical of Amgen Drug Ahead of Panel

Updated with analyst comments.

THOUSAND OAKS, Calif. (TheStreet) -- Amgen's(AMGN) effort to expand the use of new drug Xgeva to prevent or delay the spread of prostate cancer to the bones of patients is being met with skepticism by U.S. regulators who question whether such a claim has merit since the drug doesn't help patients live longer and may cause more side effects.

The U.S. Food and Drug Administration released its critique of Xgeva ahead of an advisory panel scheduled for Wednesday. Amgen already markets Xgeva for the treatment of bone-related side effects in patients being treated for cancer. The biotech firm wants FDA permission to expand Xgeva's label to allow the drug to be used to prevent or delay bone metastases in advanced prostate cancer patients.

Amgen shares were down 1% to $68.50 in early Monday trading. Investors have generally not expected Amgen to come out a winner at Wednesday's advisory panel and sales forecasts for Xgeva in this expanded indication are modest if they're modeled at all.

In a phase III study which enrolled men with advanced prostate cancer at high risk for spreading to bone, treatment with Xgeva significantly improved median bone metastasis-free survival by 4.2 months compared to a placebo. Xgeva also delayed the time to first bone metastases and reduced the risk of painful bone metastases. What Xgeva did not do, however, was help delay the growth of prostate cancer or help patients live longer. Xgeva also caused more side effects, most notably an increase in the number of patients reporting damage to the bones in their jaw.

"Though the study met the pre-specified primary endpoint, with a statistically significant prolongation in BMFS, it is unclear whether an improvement in median BMFS by 4.2 months alone in patients with CRPC at high risk for bone metastases is an adequate measure of clinical benefit," said the FDA in its review of the Xgeva data.

Amgen is expected to argue that Xgeva is providing a clinical benefit because prostate cancer that spreads to bone causes patients significant pain and leads to historically poorer outcomes. Some cancer experts on a previous FDA-sponsored panel sided with this view but also said that a 6-month improvement in bone-metastasis free survival was a clinically meaningful benefit.

Wednesday's FDA advisory panel isn't likely to recommend an expansion of Xgeva label because the panel is stacked with oncologists, who typically want to see new prostate cancer drugs demonstrate a survival benefit, said Deutsche Bank biotech analyst Robyn Karnauskas in an email to clients Monday morning. Karnauskas added that Amgen would have more of a fighting chance had more urologists been seated on the panel, since they are more favorably inclined to agree with Amgen's case.

Analysts are currently forecasting $3 billion in sales of Xgeva and its sister drug Prolia by 2015, which does not assume any sales from prevention of bone metastases in prostate cancer, she says.

--Written by Adam Feuerstein in Boston.

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