A hormone patch that works to restore a woman's sex drive should not be approved until more studies are completed to determine the drug's risks, federal health advisers said Thursday.
Several members of the Food and Drug Administration advisory committee said they were not satisfied with the number of women studied so far, the length of the studies and the modest benefits of the drug.
Procter & Gamble sought to market the testosterone patch Intrinsa to women who lost their libido after their ovaries were removed. The company told the panel had not raised significant safety concerns in clinical trials, and it urged the panel not to delay approval of the first drug for female sexual dysfunction.
However, the advisory committee was unanimous: More safety data were needed.
Clinical trials showed that women using Intrinsa had modest improvements to their sex lives. Women who applied the patch to their abdomen twice weekly had one more "satisfying sexual event" per four weeks, compared with a placebo, according to the data presented to the panel.
One hundred women needed to use Intrinsa for 15 to experience a beneficial effect due to testosterone, Dan Shemas, director of FDA's division of reproductive and urologic drugs, told the panel.
Agency officials also noted a lack of controlled safety data for women who had used Intrinsa longer than six months.
The panel heard testimony that three of four women who developed breast cancer during the clinical trials were using Intrinsa.
Lisa Soule, a medical officer in FDA's division of reproductive and urological drugs, said those breast cancer cases pointed to the limitations of short-term clinical trials.
Soule dismissed as inadequate Procter & Gamble's suggested postmarketing study comparing 5,500 women expected to use Intrinsa in the first year against matching women from a database of 10 million patients for rates of cancer and cardiovascular disease.
A federally funded research project, by contrast, had to enroll nearly 17,000 postmenopausal women to begin to detect the safety problems with hormonal therapy, Soule said.
The Women's Health Initiative, a program established by the National Institutes of Health, found that postmenopausal women taking the hormones estrogen and progestin had higher risks of heart attack, stroke and breast cancer.
Debate lingers about hormonal therapy's culpability for some ailments. But everyone agrees that hormone replacement therapy increases the risk of development of clots in blood vessels, said Dr. Charles Lockwood.
"There is just no doubt. And no debate. And no discussion about that," said Lockwood, an expert in maternal fetal medicine at the Yale University School of Medicine and a member of the panel. "So, 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 thromboembolic disease."
About 3 million women whose ovaries were removed would have been eligible to use the Intrinsa patch, according to the company. However, it was widely expected that it also would have been used off-label by women who wanted to increase their sex drive with a drug hyped as a female version of Viagra.
Dr. Steven Nissen, a cardiologist at the Cleveland Clinic Foundation and a member of the panel, said he was worried about exposing several million American women to heart attack and stroke risks to gain one additional sexual encounter a month.
"It is not an acceptable tradeoff and we cannot allow this to move forward until we have more data," Nissen said.
Joan Meyer, senior director of new drug development for Procter & Gamble, said before the vote, "It is not uncommon to have unanswered safety questions at approval."
Meyer 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.
The federal advisers' recommendations will go to the FDA, which is not bound by the recommendation but usually follows it. The agency's approval decision for Intrinsa is expected within weeks.
Although the drug is sometimes referred to as a female Viagra, it actually works differently from the drug for male sexual dysfunction. Viagra works to enhance a man's ability to have sex; Intrinsa increases a woman's desire for it.
Removal of ovaries can cause women's testosterone levels to drop by 50 percent.