For women hoping to jump-start sputtering sex drives, the Food and Drug Administration's approval of Addyi on Tuesday may be just the first step.
Don't expect 26 products -- the number of FDA-approved drugs for men's sexual dysfunction -- anytime soon. The pipeline for treatments targeting female sexual dysfunction is not currently clogged with candidates.
But experts in women's health said the FDA's Addyi decision is likely both to encourage research and development in the area and to ease the regulatory path for companies offering such drugs for women.
"This opens a big door to research on women's sexual dysfunction coming down the pike," said Florida gynecologist Maureen Whelihan, who specializes in treating women with sexual problems. "Just the fact that we're just talking about it now is energizing."
One candidate drug is nearly poised for FDA consideration. In early clinical trials, an experimental medication called bremelanotide has been shown to act on a small cluster of neurons in the brain's hypothalamus to stimulate sexual arousal. The medication, now in the final phase of recruiting patients for late-stage clinical trials, could come before the FDA in early 2017.
With the FDA's Addyi decision, "you begin to have a regulatory precedent, a pathway to follow," said Carl Span, president and chief executive officer of Palatin Technologies Inc., which is developing bremelanotide.
In addition, Sprout Pharmaceutical CEO Cindy Whitehead said in an interview that the company will "absolutely" pursue further testing of Addyi in a bid to expand the FDA's approval of the drug for women undergoing menopause and beyond. While such women will be able to access the new drug from physicians willing to write an "off-label" prescription, an expanded FDA indication would allow Sprout to market Addyi to such women as a safe and effective treatment for low sexual desire.
This week, Palatin applauded the FDA's decision on Addyi (whose chemical name is flibanserin), calling it a "long-awaited milestone" that validates the need for treatments for women suffering low sexual desire.
Unlike flibanserin (which is taken daily over a long period), bremelanotide is a fast-acting medication that is designed for "as needed" use. It is thought to work to stimulate arousal within 30 to 60 minutes of a small subcutaneous injection, and to continue to be effective for about eight hours.
Span said that, if both flibanserin and bremelanotide were available to women with flagging sex drives, the two "could provide a robust set of treatment options."
Like Addyi's sponsor, Sprout Pharmaceuticals, Palatin expects to ask the FDA first for permission to market bremelanotide to premenopausal women with a distressing lack of sexual desire -- a population estimated at about 2 million.
In an October 2014 meeting, the FDA recognized female sexual dysfunction as an "area of unmet need" and gathered interested drug makers and patient groups to define which conditions might be amenable to drug therapy and how the agency would assess the effectiveness of candidate drugs.
The resulting clarity, said Span, cleared "some very big hurdles" for companies developing sexual health drugs for women. In its wake, he added, raising funds from investors got noticeably easier.
So far, the initiatives have left post-menopausal women with sexual dysfunction little better off. The FDA in 2013 approved Osphena (ospemifene) to treat painful sex during menopause, a common sexual complaint in women beyond middle age. In 2004, the agency denied approval to Procter & Gamble to market a testosterone patch -- Instrinsa -- in the United States.
Intrinsa was later approved and widely used in Europe and Australia by women as a treatment for low sexual desire. Recent clinical trials have found it boosted the frequency of sex in post-menopausal roughly on a par with Addyi's effectiveness. But in 2012, the company that made Instrinsa withdrew it from the market in Europe.
Will "Even the Score" -- the public campaign that controversially lodged accusations of gender bias in FDA deliberations -- play a role in pressing for further research and development? The coalition was initiated and funded by Sprout, but attracted support from some feminists, patient groups and consumer advocates.
"I think they made their point, that there was a conscious or unconscious stigma against approving a drug in this category for women," said Phyllis Greenberger, executive director of the Society for Women's Health Research, which joined Sprout's coalition. "I think this was sort of a one-time thing. This was, I think, very unique."