Shares of Amgen Inc., which has a drug-manufacturing plant in West Greenwich, reached their highest point in more than a year yesterday, buoyed by positive study results on the company’s next possible blockbuster drug, the osteoporosis treatment denosumab.

The stock hit $62.50 at one point during the trading session, marking more than a 12-percent jump and its highest level since May 2007. It closed up $6.56, or 12.2 percent, at $60.48, and rose a further $1.22 to $61.70 in after-hours trading.

Second-quarter profit at Amgen, the world’s largest biotechnology company, slipped as a series of restructuring and other charges further stunted a second quarter already hit by a continued decline in anemia drug sales. But the results topped Wall Street forecasts after excluding the charges and beat analysts’ estimates after sales of its top-selling anemia drugs declined less than expected. The company also raised its 2008 earnings forecast.

“Our business showed good stability through the first half of the year, giving us confidence to increase our previously issued guidance on a full year basis,” chairman and chief executive officer Kevin Sharer said in a statement. “We are very pleased with the denosumab Phase 3 results in postmenopausal osteoporosis from the (denosumab) study and are looking forward to presenting these data in detail at a scientific conference this fall.”

Second-quarter net income dropped 7.7 percent to $941 million, or 87 cents a share as sales of the anemia medicines, Aranesp and Epogen fell, the Thousand Oaks, Calif.-based company said in a statement. Profit excluding certain costs was $1.14 per share exceeding the $1.03 average estimate of 19 analysts surveyed by Bloomberg.

This was an “overall, stellar quarter; all major products beat estimates,” said Mark Schoenebaum, an analyst with Deutsche Bank in New York, in a note to clients.

Amgen shares plunged 32 percent last year after its anemia medications were linked to risks of heart attack, stroke and death at high doses, hurting sales. The company is betting on denosumab, shown to prevent fractures in a July 25 study of 7,800 women.

Amgen raised its full-year 2008 earnings forecast, excluding some items, to $4.25 to $4.45 a share from a previous projection $4.00 to $4.30.

Revenue rose to $3.76 billion from $3.73 billion. Worldwide sales of Aranesp, the company’s top-selling product for anemia caused by chemotherapy, fell 13 percent to $825 million, from $949 million a year earlier. That beat analysts’ $740 million sales projection for the quarter, Schoenebaum said.

Sales of Epogen, an older anemia drug for patients with chronic kidney disease, were flat at $622 million, compared with $624 million a year earlier. Analysts had forecast $582 million, Schoenebaum said.

Rhode Island-manufactured Enbrel, a treatment for rheumatoid arthritis and psoriasis, generated $841 million in revenue in the second quarter, up 2 percent from a year earlier.

The three-year drug trial of 7,800 women with osteoporosis found that denosumab strengthened bones and reduced broken bones in the spine, hip and other locations more than a placebo, the biotechnology company said in a statement.

More than 200 million people worldwide, including 25 million in the United States, have osteoporosis, a disease that causes bones to deteriorate and break. The condition mostly affects elderly women, although 20 percent of cases are in men. Research has already shown that denosumab strengthens bones better than the top drug for osteoporosis, Merck & Co.’s Fosamax, which had $3 billion in sales last year.

“This is the best outcome Amgen could have hoped for, and assures denosumab’s blockbuster status,” said Michael King, an analyst with Rodman & Renshaw in New York, in an e-mail interview

“This is an extremely promising data set, and it bodes well for post-menopausal women,” said Roger Perlmutter, Amgen’s executive vice president for research and development. “The fracture reduction was statistically significant in vertebral, non-vertebral and hip fractures, compared with a placebo.”

Side effects, including infections that appeared in an earlier study, occurred no more frequently with denosumab that with a placebo in the trial, Perlmutter said.

The full study results will be presented at the annual meeting of the American Society of Bone and Mineral Research in Montreal in September, he said. Amgen will use the data to seek U.S. regulatory approval for denosumab as an osteoporosis treatment late this year or early next year.

Denosumab, a genetically engineered antibody, is designed to block the action of a protein called RANK Ligand, which leads to the breakdown of bones.

Not all investors are convinced denosumab can bring enough revenue to spur a turnaround for Amgen. Sales of Epogen and Aranesp, which fell 8 percent to $6.6 billion last year, plunged 20 percent in the first quarter of 2008, to $1.3 billion.

“Denosumab is going to be a big drug, but it’s not going to stabilize the company,” said Jon Fisher, a portfolio manager at Fifth Third Asset Management in Minneapolis, earlier this month.

With Associated Press reports