Pfizer Inc.'s Fablyn, an experimental treatment for women with weak bones, has benefits that outweigh its risks, U.S. advisers said. However, a panel of medical experts suggested the drug be restricted to women at high-risk of fracture or those who fail other treatments.

Last week, U.S. health regulators released their review on co-developers Pfizer Inc and Ligand Pharmaceuticals´s experimental treatment for osteoporosis Fablyn stating that the analysis of clinical trials showed a higher proportion of deaths of patients taking the drug than those on placebo. The higher proportion of deaths was statistically significant for the lowest dose of the drug said the FDA reviewers. A higher percentage of patients also developed blood clots. The FDA staff said Fablyn was effective for preventing fractures, and they would be asking the advisory panel if the drug´s overall safety was acceptable.

Today, the Food and Drug Administration panel made the recommendation for postmenopausal women with osteoporosis in a 9-3 vote today. They also found Pfizer lacked enough data to show whether more deaths among patients using Fablyn in a trial reflected a true result.

Fablyn – generically lasofoxifene tartrate - was designed for postmenopausal women, regulating the hormone estrogen. In August 2005, Pfizer had filed for the drug´s approval as an osteoporosis treatment. An additional NDA for the drug – then called Oporia - was filed in December of the same year as a treatment for vaginal atrophy.

Pfizer had received a “not approvable” letter from the FDA for the drug for the prevention of post-menopausal osteoporosis in September 2005, and another in January 2006 for the second application as a treatment for vaginal atrophy.

Fablyn was jointly developed by Pfizer and Ligand Pharmaceuticals, and if approved, while Pfizer holds the worldwide marketing rights, Ligand will receive royalty payments equivalent to 3 percent of net sales and an initial cash payment.

Analysts estimate the drug could bring in peak sales of $1 billion.

Fablyn belongs to a group of medicines that work like the hormone estrogen in some parts of the body and not in other parts. These drugs, called selective estrogen receptor modulators (SERMs), may exert beneficial effects in some tissues without the side effects associated with estrogen. Eli Lilly & Co.'s Evista and Schering-Plough´s Livial belong to that category.