* Jaw deterioration seen in 2 pct of denosumab patients
* Rates of new malignancies similar between study groups
* Amgen shares rise 0.6 percent (Adds study details, analyst comment, background, share price, byline)
By Deena Beasley
LOS ANGELES, Dec 10 Amgen Inc's (AMGN.O) experimental drug denosumab reduced the risk of serious bone complications among patients with advanced breast cancer by 23 percent compared to Novartis AG's NOVN.VX Zometa in a late-stage study.
Details of the study, for which overall results were announced in July, were presented on Thursday at a medical meeting in San Antonio, Texas.
The Phase 3 study assessed the incidence of serious bone complications, or SREs, among 2,046 such patients, including fractures and the need for radiation or surgery to bone.
BMO Capital Markets analyst Jason Zhang said most of the study data has already been made public, and the big question is when the U.S. Food and Drug Administration will respond to Amgen's application to market denosumab for treating and preventing bone loss in breast and prostate cancer patients.
Such patients are prone to bone complications.
The FDA in October delayed approval of denosumab as a treatment for osteoporosis in post-menopausal women. The FDA said it was seeking more information about a program to monitor the drug once on the market as well as updated safety data.
Overall incidence of serious side effects in the breast cancer trial was consistent with that seen in earlier studies of denosumab and Zometa, Amgen said.
Adverse events potentially associated with renal toxicity occurred in 4.9 percent of patients treated with denosumab and 8.5 percent of Zometa patients. Osteonecrosis, or deterioration, of the jaw was seen in 2 percent of denosumab patients and 1.4 percent of Zometa patients.
Rates of new primary cancer malignancies were 0.5 percent in both groups.
Time to disease progression or overall survival was also balanced between the study arms, according to Amgen.
Analysts view denosumab, which would have the brand name Prolia, as a potential blockbuster and the key to jump-starting growth at Amgen, the world's biggest biotechnology company.
The twice-a-year injection is expected to compete in an $8 billion market for osteoporosis treatments, with the cancer market potentially bringing in additional billions.
Denosumab works differently from current medicines by targeting a protein that activates bone-destroying cells.
Shares of Amgen were up 31 cents at $56.39 in afternoon trade on Nasdaq. (Reporting by Deena Beasley; editing by John Wallace)