WASHINGTON -- A hormone patch that works to restore a woman's sex drive should not win government approval until more studies are completed to determine the drug's risks, federal health advisers recommended Thursday.
Several members of the Food and Drug Administration's 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 committee that significant safety concerns had not come up in clinical trials and that there was no reason to delay approval of the first drug for female sexual dysfunction.
But the committee unanimously sided on the need for more safety data.
The company said in a statement it would work closely with the agency "to agree on a practical approach to provide additional safety data."
The FDA is not bound by the committee's recommendation, although the agency usually follows the guidance. An agency decision on Intrinsa is expected in a few weeks.
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 than did women given a placebo, according to the data presented to the advisory panel.
Fifteen of every 100 women who used Intrinsa experienced a beneficial effect due to testosterone, said Dan Shemas, director of the FDA's division of reproductive and urologic drugs.
By a 13-4 vote, federal advisers said that benefit was not "clinically meaningful."
Agency officials also noted a lack of controlled safety data for women who had used Intrinsa for more 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 the FDA's division of reproductive and urological drugs, said those cases pointed to the limitations of short-term clinical trials.
Soule dismissed as inadequate Procter & Gamble's suggested post-marketing 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 post-menopausal 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 post-menopausal women taking the hormones estrogen and progestin had higher risks of heart attack, stroke and breast cancer.
There is debate about how much hormonal therapy is to blame for some ailments. But there is general agreement that this treatment 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 blood clots.
About 3 million women whose ovaries were removed would have been eligible to use the Intrinsa patch, according to the company. It was expected that the product also would have been by other 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 women to heart attack and stroke risks in order to gain one more "satisfying sexual event" per month.
"It is not an acceptable trade-off 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 the additional safety data includes 100 more women who have used the patch for 18 months. Eighty women have been using the product for three years.
Unlike Viagra, which 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. Even though men make far more of this hormone than women, women still need a certain amount of it to have healthy sex lives, experts say.
On the Net:
Food and Drug Administration: http://www.fda.gov/
Procter & Gamble: http://www.pg.com