BOSTON ( TheStreet) -- An experimental drug from Germany's Bayer and the Norwegian biotech firm Algeta extended the lives of advanced prostate cancer patients by zapping tumors that invade bone with small doses of radiation, according to data from a late-stage study presented this weekend.

The Bayer/Algeta drug known as Alpharadin was hailed as a major advance in prostate cancer treatment by experts at a European cancer research meeting in Sweden because the drug is the first to improve bone symptoms and prolong survival.

Bayer plans to seek U.S. approval of Alpharadin in the middle of 2012. The emergence of Alpharadin complicates and may even block efforts by Amgen ( AMGN) and Exelixis ( EXEL) to advance their respective prostate cancer drugs.

Amgen's Xgeva is approved as a treatment for bone-related complications of cancer and the company is now seeking FDA approval to expand the drug's use to include a claim that it can delay the spread of prostate cancer to bone. Xgeva, however, does not help prostate cancer patients live longer.

Exelixis' experimental cancer drug cabozantinib, like Alpharadin, specifically targets prostate cancer that spreads to bone, but has not yet demonstrated that it can prolong survival. Exelixis is seeking FDA permission to conduct a registration study of cabozantinib that would rely on pain reduction and bone scan resolution as primary endpoints and the basis for the drug's approval.

FDA may balk at Exelixis' request without data showing that cabozantinib also helps patients live longer, especially now that Alpharadin has set a new standard for treatment.

"Alpharadin raises the bar for Exelixis. They have to produce overall survival data now," said Sally Church, a cancer drug consultant with Icarus Consultants who also co-writes the widely followed Biotech Strategy Blog.

"Alpharadin's overall survival data doesn't change our strategy," said Exelixis spokesman Charles Butler, in an email response to questions about the Bayer/Algeta drug.

Bayer/Algeta's Alpharadin, also known as Radium-233 is a new type of drug that delivers small, short-ranged doses of alpha radiation directly to prostate cancer that has spread to bones. The so-called "alpha pharmaceutical" specifically targets bone lesions with its radiation because it contains radium, which like calcium, sticks to bones. As a result, Alpharadin doesn't negatively affect surrounding, healthy tissue.

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