Pfizer Inc announced the Food and Drug Administration (FDA), which was supposed to make a decision to approve the company´s osteoporosis candidate Fablyn (generically lasofoxifene tartrate), by the end of October, has said it will be taking an additional three months to review data from a five year study not included in the original analysis, which was based on three-year data.

The extension means a decision won´t come until January, a Pfizer spokeswoman said. Fablyn has been jointly developed by Pfizer and Ligand Pharmaceuticals.

Last month, the FDA said it was concerned that Fablyn puts patients at a higher risk of death than a placebo. Pfizer, on the other hand, has said the increased number of deaths appears to be due to an unusually low mortality rate for the placebo group during the study period.

In September, an FDA panel of outside medical experts stated Fablyn has benefits for postmenopausal women, but suggested the drug be restricted to women at high-risk of fracture or those for who other treatments fail.

A rejection of Fablyn would be a setback for Pfizer, as analysts estimate the drug could bring in peak sales of $ 1 billion dollars.

Fablyn belongs to a group of medicines that work like the hormone estrogen in some parts of the body and not in others. These drugs, called selective estrogen receptor modulators, may exert beneficial effects in some tissues without the side effects associated with estrogen. Eli Lilly & Co.'s Evista osteoporosis drug is in this class, and had earnings of $ 540 million dollars in the first six months of this year.

Fablyn has been before the FDA twice before: in 2005, the FDA rejected Pfizer´s application of the drug - then called Oporia - for prevention of osteoporosis; and in 2006 rejected it for a second indication of vaginal atrophy, both times because of concerns about increased risk of endometrial cancer.

Pfizer resubmitted the drug with all-new data last December 2007 as Fablyn, for the treatment of osteoporosis.