An experimental oestrogen lotion reduced hot flushes by 85 per cent in post-menopausal women, according to results from a pivotal-stage trial of the drug Estrasorb.
If approved by regulatory authorities, it would be the first oestrogen replacement therapy in lotion form.
The drug's developer, Novavax, said the phase three, 200-patient trial also showed that about half the patients on the drug reported no hot flushes over a seven-day period after 10 weeks of treatment compared with less than 10 per cent of patients on placebo.
Shares of Columbia, Maryland-based Novavax rose 69 cents, or 6.6 percent, to close at $11.18 on Nasdaq. The trial results were presented at a meeting of the Society for Gynecologic Investigation in Los Angeles last week.
The study, which enrolled women who were naturally or surgically menopausal, consisted of a three-week screening period, a one-week placebo period, and a 12-week treatment period. The lotion, either active or placebo, was applied daily, like a cosmetic lotion, to each woman's thigh and calf.
Novavax used nanoparticle technology to develop the skin-absorbed oestrogen lotion with the aim of reducing the chance of skin irritation, a common side effect of drugs delivered through transdermal patches.
Side effects of Estrasorb were similar to placebo and consistent with oestrogens as a class, with the most common being endometrial disorder, breast pain, vaginal bleeding and infection, the company said.
Researchers believe hot flushes, which are not a health risk but are uncomfortable and stressful, stem from decreasing levels of oestrogen associated with menopause. When synthetic oestrogen is given to replace natural oestrogen in the body, hot flushes disappear.
About 38 per cent of post-menopausal women in the United States currently receive oestrogen replacement therapy - mainly in pill form, Novavax said.
Current hormone replacement therapies are also known to reduce the risk of osteoporosis, but are also associated with increased risk of certain cancers and their effect on heart disease remains the subject of debate.
Novavax and King Pharmaceuticals, its promotion partner, last year filed for US Food and Drug Administration approval of Estrasorb for the treatment of moderate to severe hot flashes and night sweats in post-menopausal women.