Amgen Inc. (AMGN) reported positive results from a second late-stage study of denosumab's usefulness in preventing complications from cancer's spread to bone, but the data disappointed those with high expectations after strong results from a similar study last month.

Nonetheless, the data should support the drug's potential approval in this usage next year, likely adding annual sales of more than $1 billion in addition to its expected approval as an osteoporosis treatment in October, according to Wall Street projections.

"[The study] still supports very strong positioning of denosumab in the market place, with a clearly positive study outcome and high likelihood of regulatory approval," wrote Sanford Bernstein analyst Geoffrey Porges.

A month ago, the Thousand Oaks, Calif., biotech reported the results of a similar denosumab trial that showed it was superior to Novartis AG's (NVS) Zometa, the current market leader in this area.

In the latest trial, denosumab met the main goal of showing it was equally effective, or "non-inferior," to Zometa, but missed a secondary goal of showing superiority.

Notably, though, denosumab showed comparable side effects to Zometa, easing concerns that complications would emerge in the cancer trials that use higher doses than osteoporosis uses.

Amgen shares recently were up 10 cents to $62.98, after trading as low as $62.12. The stock isn't far from its 52-week high of $66.51 reached in September.

The Food and Drug Administration is currently reviewing denosumab for treating osteoporosis and bone loss caused by hormone treatment in patients with breast and prostate cancer. The agency is expected to make a decision in mid-October, and an advisory panel of outside experts will review the application next week.

Leerink Swann analyst Joshua Schimmer, valuing Amgen shares at $73, projects worldwide denosumab sales of more than $3 billion by 2014, including osteoporosis and cancer-related uses.

Amgen hasn't disclosed its regulatory filing plans for preventing cancer-related skeletal complications, but Schimmer expects a launch in the third quarter of 2010. He expects sales for osteoporosis to begin in the first quarter.

Although the latest head-to-head study didn't show superiority to Zometa, denosumab patients had a longer delay in occurrence of the first skeletal event, but the difference wasn't statistically significant.

Analysts highlight that the trial included a wide mix of patients - all types of solid tumors, excluding breast and prostate cancer, and a type of blood cancer called multiple myeloma - which could make it harder to show superiority. The previous trial included only breast cancer patients.

"These results are more similar to the breast cancer result than different," Porges said.

Amgen expects to report the full details from the studies at a medical meeting later this year. The results of a third similar study in patients with prostate cancer will come in 2010.

The latest study showed serious side effects were consistent with previous studies of the two drugs, but osteonecrosis of the jaw, a serious problem that has been connected to bisphosphonates like Zometa in the past, was seen infrequently in patients taking both drugs. The condition hadn't appeared in previous studies of denosumab.

Also balanced was the incidence of osteonecrosis of the jaw, a serious problem that has been connected to bisphosphonates like Zometa.

In the latest study, 10 patients had the condition, compared with 11 patients receiving Zometa. In the breast cancer study, the condition occurred in 20 denosumab patients and 14 Zometa patients, a difference that wasn't statistically significant.

In late July, Amgen reached a deal with GlaxoSmithKline PLC (GSK) that allows the European drug giant to sell denosumab to osteoporosis patients in Europe and other overseas markets. Amgen plans to sell the drug alone in all indications in the U.S., and in cancer-related areas in most overseas markets.

-By Thomas Gryta, Dow Jones Newswires; 212-416-2169; thomas.gryta@dowjones.com