Last Updated: 2012-02-06 10:40:34 -0400 (Reuters Health)
By Anna Yukhananov
WASHINGTON (Reuters) - Reviewers from the U.S. Food and Drug Administration said on Monday that they were not sure whether Amgen Inc's Xgeva bone drug should be approved for a wider use of delaying the spread of cancer to the bone.
The injectable drug is already approved to prevent fractures caused by cancer that has spread to the bone, and it is seen as one of the most important growth drivers for the world's largest biotechnology company.
Xgeva delayed the spread of cancer to the bone by a little longer than four months in a clinical trial of 1,432 men with prostate cancer who had stopped responding to hormone therapy.
Amgen said the drug would be targeted at about 50,000 men in the United States at that stage of the disease.
The FDA staff said it was unclear whether that length of time without cancer spreading was "an adequate measure of clinical benefit," especially as the drug did not help men live longer or delay the growth of prostate cancer.
Reviewers were also concerned that about one in 20 men treated with the drug developed osteonecrosis of the jaw, or death of jawbone tissue, and said it was uncertain whether the rate could be even higher if patients take the drug for a longer time.
An advisory committee will vote Wednesday on whether to recommend approval of the drug for the wider use. The FDA will make a final decision later.
ISI Group analyst Mark Schoenebaum said the critical review of Xgeva was expected, since the FDA had previously questioned whether a delay in cancer spreading to the bone was a meaningful benefit to patients.
"Even if the panel votes in favor of approval, commercial demand could be modest," he added in a note, and said sales could reach about $300 million a year.
In the fourth quarter of 2011, sales of Xgeva rose to $134 million from $100 million in the prior quarter.
Amgen is hoping a broader use will significantly accelerate sales of the drug. Xgeva, along with related osteoporosis drug Prolia, are expected to offset declining sales of the anemia drugs that had been the company's backbone.
The company said it would tell the advisory committee that Xgeva provided a meaningful benefit to prostate cancer patients by preventing the spread of their disease to the bones, which often happens.
"Bone metastases ... are irreversible and progressive, and contribute major morbidity to these patients," the company said in a statement. Amgen said that if Xgeva is approved, it would be the first drug to delay the spread of cancer to the bone for men with prostate cancer.
Amgen said it was also testing Xgeva in other cancers, including breast and lung cancer and multiple myeloma, or cancer of a type of white blood cell.
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