However, repeated delays in developing the new drug, Aprela, have raised questions about its potential. Some analysts and doctors question whether regulators will approve it, and Aprela's market potential could be limited by continued safety concerns about hormone-based drugs.
The New York-based drug maker expects to submit Aprela for Food and Drug Administration approval sometime this year, according to Olivier Brandicourt, president and general manager of Pfizer's primary-care unit. He discussed Aprela in an interview earlier this month.
Mr. Brandicourt said the drug has the potential to reduce menopausal symptoms such as hot flashes and to prevent bone-thinning osteoporosis, but with a better safety and tolerability profile than older hormone-replacement therapies.
Many women stopped using hormone-replacement therapies after a government study, the Women's Health Initiative, raised safety concerns a decade ago.
PremPro, which Pfizer acquired with its purchase of Wyeth in 2009, was shown to increase risk of breast cancer. A similar drug, Premarin, has been tied to increased risk of uterine cancer, and both drugs have been linked to risks for stroke and certain blood clots. Pfizer has set aside more than $800 million to cover previous and potential settlements and judgments for lawsuits alleging injuries caused by hormone-replacement therapies.
Aprela contains an active ingredient found in the older drugs, known as conjugated estrogens, which are derived from the urine of pregnant horses. But Aprela combines conjugated estrogens in a single pill with another drug, bazedoxifene, that may mitigate the risks of conjugated estrogens alone.
Bazedoxifene is a selective estrogen receptor modulator, or SERM, the same category as Eli Lilly & Co.'s Evista, which is approved to prevent and treat osteoporosis. A SERM is designed to provide the benefits of estrogen while mitigating the negative effects of estrogen such as increased risk of uterine cancer. Pfizer, via Wyeth, licensed bazedoxifene from Ligand Pharmaceuticals Inc.
However, Aprela's development has taken longer than expected. The FDA declined several years ago to approve bazedoxifene as a stand-alone drug because regulators wanted more information about the incidence of strokes and certain blood clots in clinical testing.
Bazedoxifene was approved by European and Japanese regulators as a stand-alone treatment for osteoporosis. It is sold in Japan as Viviant and Conbriza in Europe.
There have also been challenges developing a satisfactory formulation of Aprela. Wyeth, which started working on Aprela in 1999, had originally planned to file for FDA approval of Aprela in 2007, but the submission has been repeatedly delayed since then. http://tinyurl.com/6qeupep