UPDATE 4-FDA OKs Amgen's bone drug in certain cancers

* Approved for patients with solid tumors

* Not approved for multiple myeloma

* Shares rise 1.6 percent (Adds trial detail in ninth paragraph)

LOS ANGELES, Nov 18 (Reuters) - The U.S. Food and Drug Administration has approved Amgen Inc's AMGN.O bone drug denosumab as a treatment for reducing fractures and other bone problems in cancer patients with solid tumors, a spokeswoman for the agency said on Thursday.

As expected, the drug, which will be sold under the brand name Xgeva, was not approved for use in patients with multiple myeloma, a cancer of the blood, according to FDA’s Erica Jefferson.

The solid tumor approval, according to some analysts, is worth annual sales of more than $1 billion.

Denosumab -- a lower dose of which is currently sold with the brand name Prolia as a treatment for osteoporosis -- had sales of $10 million in the third quarter.

Goldman Sachs analyst Sapna Srivastava recently forecast 2013 denosumab sales of $1.3 billion, which is lower than the average analyst estimate of $2 billion.

The analyst, who rates Amgen shares as “sell,” said the drug’s comparatively high price and safety issues will limit sales.

“In Phase III trials, denosumab-treated patients have had more cases of osteonecrosis (bone death) of the jaw and higher new malignancy rates versus Zometa,” Srivastava said in a research note.

The FDA said denosumab's safety and efficacy was confirmed in three clinical trials, including a study in prostate cancer patients which found that the median time to a fracture or other bone problem was 21 months, compared to 17 months for patients treated with Novartis AG's NOVN.VX Zometa.

Another trial involving breast cancer patients has concluded, and also showed that denosumab worked better than Zometa. The third trial, which involved patients with a variety of tumor types, including multiple myeloma, showed similar results for both drugs.

“A diagnosis of bone metastases is a major event for patients living with cancer, and the consequences can be devastating,” Amgen Chief Executive Officer Kevin Sharer said in an emailed statement.

Amgen is expected to announce before the end of the year results from a critical trial looking at whether denosumab can prevent prostate cancer from spreading to bone. That indication could add billions of dollars more in sales.

Denosumab is the first in a new class of medicines that work by blocking a protein which activates bone-destroying cells called osteoclasts.

Shares of Amgen, which rose 2.4 percent in regular trading, were up another 1.6 percent at $56 in after hours trading. (Editing by Carol Bishopric)