Expert Commentary

Flibanserin is poised for FDA approval. But why this drug? And why now?

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Women with hypoactive sexual desire disorder have long sought a remedy for this common complaint. With an advisory committee recommending approval of flibanserin, their wait may be over.


 

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Women’s sexual health took a step forward last month when an advisory panel to the US Food and Drug Administration (FDA) recommended approval of the drug flibanserin for the treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women. The approval came with some reservations regarding safety (use with certain medications and alcohol). And it’s worthwhile to note that the FDA had on hand its own Drug Safety and Risk Management Committee during deliberations. However, assuming the agency follows the recommendations of the Bone, Reproductive, and Urologic Drugs Advisory Committee, women will soon have available the first agent for sexual dysfunction—aside from a medication for intercourse-associated pain—developed specifically for them.

Had the panel voted down the approval, it would have set a dangerous precedent that likely would have led to a standstill in new drug development in all therapeutic classes of women’s sexual health for the next decade.

Why do I say that—and state it so emphatically?

To answer that question, let’s review the approval process for flibanserin, as well as for the 2 testosterone products that preceded its appearance before the FDA.

Hypoactive sexual desire disorder (HSDD) is the most common sexual dysfunction in women. Few interventions have proven to be effective for the treatment of HSDD. Education, counseling, and psychotherapy may be helpful in some women. Exogenous testosterone has been reported to be effective in the treatment of low sexual desire in postmenopausal women taking estrogen, but this treatment is not approved by the US Food and Drug Administration (FDA), and the long-term safety of exogenous testosterone in women is not established. Clinicians who treat women with sexual desire disorders are frustrated by their inability to prescribe an effective treatment for this common problem. An FDA advisory panel recently voted to support the approval of flibanserin for the treatment of HSDD in premenopausal women. In this month’s editorial, Dr. James Simon provides a history of the FDA review process for medications designed to treat HSDD, including the decision to not approve testosterone and the vote of the FDA advisory panel to support the approval of flibanserin. Readers of OBG Management should be aware that Dr. Simon, as is apparent in this piece and fully disclosed, has served as Medical Director and an advisor to Sprout Pharmaceuticals, the company with the rights to flibanserin. As editors we have concluded that Dr. Simon’s unique perspective, knowledge, and insights about the history of the FDA review of treatments of HSDD, including testosterone, would be of great interest to our readers.
—Robert L. Barbieri, MD, Editor in Chief
—Lila O’Connor, Editor

A tale of 2 products: The testosterone story
In 2004, Procter & Gamble filed a new drug application (NDA) for a testosterone patch (Intrinsa) developed for the treatment of female sexual dysfunction. Specifically, the patch was created for the treatment of HSDD in surgically menopausal women (those who had undergone bilateral oophorectomy) who were receiving concomitant estrogen therapy.

Both the FDA and the advisory committee considering the NDA agreed that the patch was effective. The question was whether its efficacy outweighed its risks. Recall that this discussion was taking place only 2 years after the initial publication of findings from the Women’s Health Initiative (WHI) estrogen-progestin arm. That arm had been halted prematurely because the risk of breast cancer exceeded the prespecified stopping boundary. In addition, the global index summarizing the balance of risks and benefits showed that risks outweighed benefits in ­regard to breast cancer, coronary heart disease, stroke, and pulmonary embolism.1 As a result, the safety of all forms of hormone therapy was being closely scrutinized.

The FDA was also on “high alert” for safety as rofecoxib (Vioxx) had just been removed from the market due to unforeseen risks, with much media fanfare and large numbers of lawsuits.

After consideration of the NDA for the testosterone patch, the FDA advised Procter & Gamble to ­undertake an adequately designed and powered safety study to confirm that it would not increase the risks of coronary heart disease or breast cancer among users, since testosterone can be converted to estradiol in women.

Procter & Gamble ultimately withdrew its NDA. Such a safety study would have taken an additional 5 years to complete and cost upwards of $300 million. And because testosterone is not a patentable compound, a study that long and costly didn’t seem like a smart business proposition. Shortly after the NDA was withdrawn, the European Medicines Agency—the European counterpart of the FDA—approved the Intrinsa testosterone patch for the same indication as proposed in the United States.

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