Amgen Bone Drug Denosumab Cleared to Treat Fractures in Cancer Patients

Amgen Inc.’s osteoporosis drug denosumab was approved by U.S. regulators for reducing fractures in prostate and breast cancer patients, an indication that may boost sales to $2.4 billion in five years.

The decision yesterday by the Food and Drug Administration moves Amgen, based in Thousand Oaks, California, into the cancer market with a drug cleared in June for treating osteoporosis in older women. Denosumab will be marketed to reduce fractures and surgery in patients whose breast, prostate or other solid tumors have spread to their bones, Amgen said in a statement.

Amgen, the world’s largest biotechnology company, is looking to denosumab to help revive growth, after revenue fell 2.4 percent last year. The drug will compete with Novartis AG’s Zometa, which had 2009 sales of $1.47 billion. Denosumab, to be sold as Xgeva, may reach sales of $2.4 billion in 2015, said Yaron Werber, a Citigroup analyst in New York.

“This is a big, important step for the company, launching a new product which will help put the company back on a growth trajectory,” Werber said yesterday in a telephone interview.

Amgen fell 14 cents, to $55, at 4 p.m. New York time in Nasdaq Stock Market composite trading. The shares have declined 1.9 percent in 12 months.

Sales of the drug may rise by an additional $500 million if the company shows, in data expected this year, that denosumab can keep cancer from spreading to bone, Werber said.

‘Enhance Appetite’

“If that works, that will make Xgeva a multibillion-dollar product globally and dramatically enhance appetite for the stock,” Werber said.

“This is the culmination of more than 15 years of effort by our company,” said Roger Perlmutter, Amgen’s executive vice president for research and development, in a telephone interview yesterday. “This discovery provides the opportunity for patients who have metastatic cancer affecting their bones to have a therapy that improves their lives.”

Denosumab targets a protein called RANK ligand that Amgen scientists discovered in the mid-1990s. This protein works with others in a process that routinely breaks down old bone in the body and replaces it with new. It also plays a role in weakening the bones of people with osteoporosis and cancer.

Bone Destruction

When women’s estrogen levels fall after menopause, or when cancer spreads to the bones from other parts of the body, the change stimulates production of RANK ligand, intensifying bone destruction. Denosumab, a synthetic version of an immune cell, inhibits RANK ligand and reduces bone destruction, Perlmutter said in a Nov. 15 telephone interview.

The most common serious side effects of denosumab seen in clinical trials were low calcium levels in the blood and osteonecrosis, or bone decay, in the jaw, Amgen said in the statement. The bone loss occurred about as often with denosumab as it did with Zometa, while low calcium was more common among users of denosumab, Amgen said. In one study of prostate cancer patients, 2.6 percent of those taking denosumab developed osteonecrosis, the company said.

In breast and prostate cancer patients, malignant cells spread to bone in about 65 percent to 75 percent of cases, according to research published in the journal Cancer in 2000. When the tumors replace healthy bone tissue, it may cause pain, swelling and fractures and need to be treated with radiation, chemotherapy or amputation.

Skeletal-Related Events

Amgen conducted a series of studies that measured how long it took on average for patients taking either denosumab or Zometa to experience their first “skeletal-related event,” a fracture, spinal cord compression, or the need for surgery or radiation.

One of these studies, submitted to the FDA, showed denosumab delayed broken bones and complications 20.7 months, or three months longer than Zometa in 1,901 prostate cancer patients whose tumors had spread to their bones. In another study of 2,046 breast cancer patients, denosumab delayed fractures or complications longer than Zometa, Perlmutter said.

Denosumab also kept fractures at bay longer than Zometa in patients with a variety of other tumor types, although the difference wasn’t statistically significant, Perlmutter said. For patients with multiple myeloma, Zometa outperformed denosumab. While the drug wasn’t approved yesterday for myeloma, Amgen is starting a new study of patients with that condition.

Osteoporosis Sales

Denosumab’s use in osteoporosis since it was approved has lagged behind analyst’s predictions. It had $10 million in sales in the quarter ended Sept. 30, below the $31 million expected by analysts surveyed by Bloomberg.

Sales for treating osteoporosis are likely to increase as doctors become comfortable with the medicine and get used to a complicated billing system, said Robyn Karnauskas, an analyst with Deutsche Bank Securities in New York, in a Nov. 15 note to investors. Use in cancer presents the biggest opportunity, she said.

That’s partly because tumor patients should get the drug 12 times a year, compared with twice-yearly shots for osteoporosis patients, Perlmutter said. The recommended dose for people with cancer is also twice as large.

To contact the reporter on this story: Rob Waters in San Francisco at rwaters5@bloomberg.net.

To contact the editor responsible for this story: Reg Gale at rgale5@bloomberg.net.

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