FDA staff note deaths in Pfizer bone drug study

WASHINGTON (Reuters) - Osteoporosis patients given a low dose of an experimental Pfizer Inc pill were more likely to die within five years than others who got a placebo, U.S. drug reviewers said in an analysis released on Thursday.

An increased death rate for women who took the highest dose of the drug Fablyn was not statistically significant in the company study, Food and Drug Administration reviewers said. That means the difference could have been due to chance.

The drug, which the FDA rejected for osteoporosis in 2005, was developed with technology from Ligand Pharmaceuticals Inc.

The FDA staff said it was "of concern" that Fablyn patients had more than double the chance of developing a blood clot in a vein. Blood clots are a known risk of similar drugs.

The agency will ask a panel of outside advisers that meets on Monday if Fablyn offers acceptable safety, the staff summary said. The reviewers said the once-a-day pill was effective for preventing fractures in post-menopausal women with osteoporosis, which weakens bones.

In a study of more than 8,500 women, 4.7 percent given the lowest Fablyn dose developed a new or worsening fracture within 3 years. That compared with 6.4 percent of placebo patients.

Pfizer said in a separate summary: "Overall (Fablyn) was not associated with an increased mortality risk."

In the company's main study, 3.2 percent of women given the low Fablyn dose died, compared with 2.3 percent in the placebo group.

The higher rate for low-dose patients "appears to be due to an unusually low mortality rate in the placebo group" in one region where the drug was tested, Pfizer said.

The causes of death were consistent with the leading killers of elderly people, including cancer and heart disease, Pfizer said.

Fablyn belongs to a class of drugs known as selective estrogen receptor modulators, or SERMs, which includes Eli Lilly and Co's osteoporosis drug Evista.

Pfizer said Fablyn "affords a unique benefit among SERMs" by reducing more types of fractures. More than 200 million people worldwide have osteoporosis, the company said.

The FDA will weigh the advisory panel's input before deciding whether to approve Fablyn. The agency usually follows panel recommendations, but is not required to.

The drug's generic name is lasofoxifene. The previous proposed brand name was Oporia.

If Fablyn is approved, Ligand will receive a milestone payment and royalties of 3 percent of net sales.

Osteoporosis drugs already sold include Procter & Gamble and Sanofi-Aventis SA's Actonel, and Boniva, sold by GlaxoSmithKline Plc and Roche Holding AG.

The generic drug alendronate, a cheaper copy of Merck & Co's Fosamax, also is available.

Pfizer shares fell 2.8 percent to close at $18.67 on the New York Stock Exchange, while Ligand dropped 2 cents to $3.32 on Nasdaq.

(Editing by Tim Dobbyn, Dave Zimmerman, Lisa Von Ahn, Gary Hill)