Amgen says denosumab improves bone vs Fosamax

LOS ANGELES (Reuters) - Amgen Inc (AMGN.O) said on Monday a trial of its experimental osteoporosis drug, denosumab, showed it increased bone density at the hip in post- menopausal women who switched from Merck & Co Inc's (MRK.N) Fosamax.

The news sent the biotechnology company's shares up 2 percent.

The one-year study of 504 patients with low bone mineral density (BMD) showed the relative magnitude of improvement at the total hip was about 80 percent greater in patients injected twice a year with denosumab, compared with the group that continued with weekly oral doses of Fosamax, also known as alendronate.

Amgen did not disclose specific results for the trial's other goals, but said patients treated with denosumab achieved significantly greater bone density gains at all sites measured.

The company said the incidence and types of side effects, including cancerous tumors and infection, were balanced between the two treatment groups.

"This is important, as many (Wall) Street observers have worried about infection risk," Bear Stearns analyst Mark Schoenebaum said in a research note.

Amgen said the most common side effects seen in the trial included back pain and joint pain.

"This is the second Phase 3, head-to-head study demonstrating that administration of denosumab resulted in superior BMD gains versus those achieved with alendronate," Roger Perlmutter, Amgen's executive vice president of research and development, said in a statement.

The biotechnology company expects results from its 8,000- patient Phase 3 study evaluating denosumab's impact on fracture risk in women with post-menopausal osteoporosis in the second half of this year.

Amgen is developing denosumab -- a bioengineered antibody that targets a protein involved with the activity of bone- destroying cells called osteoclasts -- as a treatment for osteoporosis patients, as well as for cancer patients whose disease has spread to the bone.

Amgen shares, which closed at $42.34 on Nasdaq, were up 2 percent at $43.26 in after hours trading.

(Reporting by Deena Beasley; editing by Carol Bishopric, Leslie Gevirtz)