An FDA advisory committee will meet next Thursday to review the latest evidence of risk for cancer patients who are treated with widely used anemia meds - Amgen’s Aranesp and Johnson & Johnson’s Procrit. The same panel met last May, but since then, new data was given the FDA from several studies showing increased risks of death or faster tumor growth. (Look here).

So Wall Street is betting that the drugs, known as ESAs, may face added restrictions. One possibility - the FDA may advise docs not to prescribe the meds for patients with breast cancer, or any cancer, according to Bloomberg News. The drugs were already restricted last year, after being tied to higher risks of heart attack, stroke and death at high doses. The FDA then told docs to use the lowest possible dosages.

“I don’t know if it can get any worse,” Eric Schmidt, an analyst with Cowen & Co., tells Bloomberg . “It’s reasonable to assume there will be more restrictions on the drugs’ use.”

Amgen stock has lost 20 percent of its value since Dec. 6, when the drugmaker disclosed discussions with the FDA about new limits on the drugs. The decline reflects a worst-case assumption by investors that FDA limits will cost Amgen all US sales of Aranesp for cancer patients, or about $1 billion a year in revenue, according to Schmidt. Aranesp, also used for kidney patients, generated $3.61 billion in worldwide sales in 2007, a 12 percent decline.

New data on Aranesp’s risks became public on Nov. 30, when Amgen issued a statement on a study called Prepare, which enrolled 733 breast cancer patients before they had surgery to remove tumors. All of the patients got chemotherapy. Of those who also received high doses of Aranesp, 50 of 356 died, or 14 percent, compared with 37 of 377 patients, or 9.8 percent, among those who didn’t take the anemia drug.

Four days later, Amgen told the FDA about a study of cervical cancer, which also found a higher risk of death for patients on the anemia drugs, Bloomberg writes. Researchers have been attempting to measure the risk across all studies. The analysis of 51 clinical trials over the past 20 years, published last month in the Journal of the American Medical Association, found the anemia drugs raised the risk of death by about 10 percent.

Based on the new information, the FDA is likely to seek added warnings in the products’ prescribing information, said Michael King, an analyst with Rodman & Renshaw, in an investor note. That alone may not hurt demand for the drugs, wrote King, who estimates there’s a 30 percent chance the FDA panel will recommend ending the use of the anemia drugs for breast cancer patients, and a one-in-10 shot that the advisers will propose doctors stop prescribing the medicines for all cancer patients.

Source: Bloomberg News