TRENTON, N.J. – An experimental menopause treatment drugmaker Wyeth is developing reduced hot flashes, trouble sleeping and other symptoms and did not increase breast tenderness, a problem that bothers many women taking menopause drugs, according to data from two studies released Thursday.

Wyeth, long a dominant player in menopause treatments, is developing a compound called Aprela that combines the hormone estrogen with bazedoxifene, part of a class of drugs called selective estrogen receptor modulators.

These drugs are thought to bring some beneficial effects of estrogen, including protecting the breast from cancer – key because an older Wyeth hormone replacement drug, the estrogren-progestin combo Prempro, was linked to increased breast cancer risk in a huge federal study.

In one late-stage study presented Thursday at The North American Menopause Society conference in Orlando, Fla., postmenopausal women getting various doses of Aprela had the same rates of breast tenderness and abnormal mammograms as the groups getting either Eli Lilly's rival drug Evista or a placebo. That's important because breast tenderness is a top reason women discontinue menopause treatment, and because Prempro and some other estrogen-like menopause treatments are thought to increase breast density, which can make it harder to read mammograms.

The 3,400 women in the study, whose average age was 57, had ceased menstruating, but many still suffered with classic menopause symptoms such as hot flashes and trouble falling and staying asleep.

The women received daily doses of Aprela for two years. There was no increased incidence of breast cancer in women taking Aprela, compared to those getting placebo or Evista, but breast cancer can take a decade to develop. Wyeth is tracking breast cancer incidence long term in other research.

It plans to apply to U.S. regulators in the second half of next year for permission to sell Aprela.

In another late-stage study of 318 postmenopausal women still enduring 50 or more hot flashes a week, those taking Aprela over three months had significant improvements in their sleep, compared with women getting a placebo, who also reported a little benefit. Those taking Aprela also reported less-severe hot flashes.

Both those studies, which were funded by Wyeth, were on women who had not had a hysterectomy.

Wyeth has previously reported in a series of late-stage studies that Aprela increases bone density, reduces vaginal dryness and improves sexual function in postmenopausal women. At high doses, Aprela has been shown to reduce excess growth of the endometrium, the lining of the uterus, a condition that can cause breakthrough bleeding and lead to cancer.

“What you want is the best of both worlds. You want to be able to treat (menopause) symptoms, you want to prevent osteoporosis, and you want to protect the endometrium,” said Dr. Ginger Constantine, head of clinical research on women's health and bone repair at Wyeth.

Sales of hormone replacement drugs topped $2 billion last year in this country alone, according to health data company IMS Health. The osteoporosis market is even bigger, with 2007 global sales exceeding $8.9 billion for drugs including Fosamax, Boniva, Actonel and Reclast.

Wyeth has been trying to get approval to sell a bazedoxifene-only osteoporosis drug, known as Viviant, for about two years, but the Food and Drug Administration has demanded additional data three times, mostly about blood clots and strokes in a small number of women tested.

A study presented on that drug, which included nearly 450 postmenopausal women with osteoporosis, found after two years on Viviant, women had slight decreases in breast density, rather than increases that have been linked to breast cancer and can make it harder to read mammograms. Comparison groups that took Evista or a placebo had similar density decreases.