New drug helps prevent osteoporosis, but the downside could be cancer

No doubt, Amgen (AMGN) and its investors would have liked the U.S. Food and Drug Administration's health panel proceedings to have gone differently. The good news coming out of the panel, held on Thursday, was that Amgen's highly anticipated bone drug, denosumab, benefits patients with osteoporosis. In fact, the experts unanimously voted that the injectable drug helped to prevent bone fractures in women with postmenopausal osteoporosis and should be used by women who have a history of fractures or are at high risk for fracture. Denosumab reduced the risk of spine fractures by 68 percent and hip fractures by 40 percent over three years compared to women not taking the drug.

But the FDA's Advisory Committee for Reproductive Health Drugs also said that the downside of using the drug was its impact on the immune system. Turns out that when tested in trials, the drug led to a slight increase in the rates of serious infections and even some type of cancers. Amgen says that it doesn't believe the drug results and that the rise in infections could simply be due to chance.

But that didn't sway the panel which recommended that women try other treatments first until more long-term safety data is available. The panel voted 12 to three against using denosumab to prevent postmenopausal osteoporosis, saying it wanted to see larger, more in-depth data before recommending it to patients who don't yet have bone disease. It also voted against the use of the drug in breast cancer patients with osteoporosis. However, the panel did vote for the drug use in prostate cancer as it appears to be safer for men.

A ruling by the FDA is due by October 19, although it could be delayed. While the agency is not required to follow the panel's advice, it usually does and Thursday's vote was definitely a step in the right direction even if it wasn't everything the biggest biotechnology company wanted.

About 10 million Americans have osteoporosis, while nearly 34 million people are at risk of the disease due to weakening bones, so it's clear why Amgen is pushing the preventive measure. The company pledged to closely monitor the long-term safety of the drug, but added that denosumab's benefits outweighed any risks.

Amgen's promising anemia drugs sales have been hit due to safety concerns and FDA-imposed restrictions and investors looked at denosumab for future growth. Just last month, investors pushed the stock 15 percent higher when clinical trials showed it worked better than current drugs on the market. Despite the setback Thursday, denosumab is still expected to achieve blockbuster status with sales between $1 billion and $2 billion a year and analysts by and large reaffirmed high expectations for the drug. Not everybody was impressed though, as Citigroup (C) downgraded Amgen from Buy to Hold and lowered its price target from $71 to $68.

Global sales of osteoporosis treatments reached $8.4 billion last year, according to data from IMS Health, including some low-cost generics, meaning Amgen will also have to compete on price.

Denosumab is a genetically engineered first fully human monoclonal antibody that specifically targets RANK Ligand, the cells that break down bone (but also play a role in the immune system). It is given as a twice-a-year injection and will be marketed under the brand name Prolia.
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