In a move that could chill excitement about experimental drugs to treat female sexual dysfunction, federal advisers refused to endorse a new testosterone patch for women.
Procter & Gamble sought to market the Intrinsa patch to women with impaired libido due to surgical removal of their ovaries. The company told a Food and Drug Administration advisory panel that the drug had not raised significant safety concerns in clinical trials.
However, the advisory committee was unanimous Thursday: More research was needed.
The FDA is not bound by the committee's recommendation, though the agency usually follows such guidance. An FDA decision on Intrinsa is expected in a few weeks.
Panel member Dr. Steven Nissen, a Cleveland Clinic Foundation cardiologist, said he worried about exposing millions of American women to heart attack and stroke risks to gain a marginal increase in sexual satisfaction.
Clinical trials showed that women who applied the patch to their abdomen twice weekly had one more "satisfying sexual event" per four weeks than did women given a placebo, according to the data presented to the advisory panel.
Nissen said Procter & Gamble needs to study at least 5,000 women for several years to see if the testosterone patch unacceptably raises cardiovascular risk. Heart disease is already the No. 1 killer of American women.
Nissen acknowledged the drug's potential. "The number of men who take Viagra is enormous," he said. "Why would women be any different? I think there's a huge demand for this agent."
Still, agency officials noted a lack of controlled safety data for women who had used Intrinsa longer than six months.
Procter & Gamble said in a statement it would work closely with the agency "to agree on a practicable approach to provide additional safety data."
The results of long-term studies by the Women's Health Initiative, a program established by the National Institutes of Health, loomed large. That project found that postmenopausal women taking the hormones estrogen and progestin had higher risks of heart attack, stroke and breast cancer.
Lisa Soule, a medical officer in FDA's division of reproductive and urological drugs, said short-term clinical trials for Intrinsa are inadequate.
Soule dismissed Procter & Gamble's suggested post-marketing study that would compare rates of cancer and cardiovascular disease in 5,500 women expected to use Intrinsa in the first year against matching women from a database of 10 million patients.
The Women's Health Initiative, by contrast, had to enroll nearly 17,000 postmenopausal women to begin to detect the safety problems with hormonal therapy, Soule said.
Because hormone replacement therapy definitely increases the risk of development of clots in blood vessels, federal adviser Dr. Charles Lockwood wanted more data on blood clotting differences with Intrinsa.
"I think if there is one single element of safety that deserves the most scrutiny, it is the potential role of this patch in promoting" blood clotting, said Lockwood, an expert in maternal fetal medicine at the Yale University School of Medicine.
Up to 3 million women whose ovaries had been removed would have been eligible to use Intrinsa, according to the company. However, it was widely expected that Intrinsa would have been used by other women who wanted to increase their sex drive with a drug hyped as a female version of Viagra.
Joan Meyer, senior director of new drug development for Procter & Gamble, told the panel the company will soon have more safety data adding information for nearly 200 women who have used the patch for one year.
The company will also provide safety data on 100 more women who have used the patch for 18 months. Eighty women have been using the product for three years.
Unlike Viagra, which enhances men's physical ability to have sex, Intrinsa boosts women's desire for it. Removal of ovaries can cause women's testosterone levels to drop by 50 percent. Although men make more testosterone, women need some to have normal sex lives, experts say.
Fifteen of every 100 women who used Intrinsa experienced a beneficial effect due to testosterone, Dan Shemas, director of the FDA's division of reproductive and urologic drugs, told the panel.
By a 14-3 vote, federal advisers said that benefit, compared with a placebo, was "clinically meaningful."
On the Net:
Food and Drug Administration: http://www.fda.gov/
Procter & Gamble: http://www.pg.com