Pfizer, the world’s biggest drugmaker, is seeking U.S. Food and Drug Administration approval for the osteoporosis drug which was rejected by U.S. regulators three years ago. A panel of medical experts on Monday said the drug had benefits for postmenopausal women, but some members suggested that the treatment for women with weak bones should be limited to those who face a higher risk of fracture. However, the panel didn’t vote on imposing limits.

Panel members concluded the drug would give women an alternative to other osteoporosis treatments, some of which have multiple side effects, and would most benefit postmenopausal women at high risk of fractures, said Chairwoman Sandra Carson, a professor of gynecology at Brown University and the panel’s chairwoman.

Scott Monroe, director of the FDA’s urologic and reproductive product division, said the panel’s vote wasn’t a “clear-cut endorsement.”

For Pfizer, the drug offers “unique benefits” for postmenopausal women at high risk for fractures, spokesman Jack Cox said in a statement.

“We believe the data presented today demonstrates that lasofoxifene offers unique benefits for the treatment of osteoporosis in women at increased risk of fractures,” Pfizer said in a statement. “We will continue to work with FDA on any outstanding questions they may have as a result of today’s discussion.”

It is unclear whether the FDA will approve the drug, Fablyn, or whether it will suggest restricting the drug to a certain population of women. The FDA usually follows panel recommendations. A ruling is expected in October.

FDA officials raised concerns in documents released before the meeting, which said that Fablyn put patients at a higher risk of death than a placebo. They added that the patients taking Pfizer’s drug were more likely to develop blood clots, but said there wasn’t enough evidence to draw a conclusion. Pfizer said the number of deaths “appears to be due to an unusually low mortality rate for the placebo group” and was not linked to the drug.

In case Fablyn receives the approval, analysts estimate that it may bring the company a profit of about $500 million in annual sales.

The drug designed to treat osteoporosis in postmenopausal women works like the hormone estrogen and like any other drugs that are named selective receptor modulators, but don’t have the side effects associated with estrogen. Its competitors include Eli Lilly & Co.’s Evista, Novartis AG’s Reclast, Roche Holding AG’s Boniva, Procter & Gamble Co.’s Actonel and Merck & Co.’s Fosamax, the latter of which was the market leader until February this year.

Osteoporosis is a major public threat which may significantly affect life expectancy and quality of life. The disease, in which the bone mineral density (BMD) is reduced, the microarchitecture is disrupted, and the amount of non-collagenous proteins is altered, leads to an increased risk of fracture. The U.S. Preventive Services Task Force recommended in 2002 that all women 65 years of age or older who are at increased risk should be screened with bone densitometry. Between 35-50% of all women over 50 had at least one vertebral fracture. Osteoporosis risk factors include: advanced age (in both men and women), estrogen deficiency following menopause, a family history of osteoporosis.