FDA advisers back an approval for Sprout's twice-rejected female libido drug flibanserin

An FDA advisory committee has given Sprout Pharmaceuticals a thumbs up on its quest to gain the first approval ever for an experimental therapy designed to heighten women's sexual desire--but the panelists also want some postapproval studies to help clarify the safety issues involved.

Eighteen of the panelists voted in favor of an approval, drawing cheers from the largely pro-flibanserin crowd, against 6 "no" votes. But all 18 votes cast in favor of flibanserin expressed a need for postapproval risk management provisions beyond simple label warnings. Many of the favorable votes came from practitioners who acknowledged that there are many unanswered questions about this drug, but felt there was enough evidence to support a near-term approval as they wait for more answers.

"It's clear to me that there were very consistent benefits in measures we understand for some portion of women," and no benefits for others, noted advisory committee member Kevin Weinfurt. "We're going to be looking to post-marketing studies" to identify who's most likely to benefit and who is most likely to be at risk.

The ball now passes to the regulators, who will consider the adcomm's position as they make a formal decision on marketing the drug. Sprout wants to market this drug as Addyi. 

The FDA has twice rejected flibanserin, sometimes touted as a "female Viagra," first when Boehringer Ingelheim pitched it in 2010 and then again in 2013 after tiny Sprout landed rights to the drug and then mounted its own campaign for an approval for hypoactive sexual desire disorder in premenopausal women.

The agency has been chilled by the weak efficacy data available for the drug, especially when weighed against potential side effects. An FDA review prepared in advance of the third review highlighted concerns that women taking the sexual-arousal drug would suffer from fainting episodes and fears that the drug could pose added problems if used during a bout of heavy drinking.

Working off a baseline of two to three satisfying sexual events (SSEs), Sprout offered data to support a median increase of 0.5 to 1.0 SSEs per month. That modest increase also raised questions with the panel about just how good a drug this is. Panelists raised questions about the likelihood that patients would forgo alcohol while taking the drug for a prolonged period, raised questions about mammary tumors seen in mice and wondered how the patient population would likely expand after an approval.

In addition to the company's defense of the data, though, a long lineup of public speakers--including some sponsored by Sprout, which has struggled to change the agency's mind and stoked a public petition on its behalf from Even the Score--demanded that the agency provide some parity to women by offering official sanction to a drug for a female sexual disorder that is currently unaddressed at a time when there are 26 drugs for male sexual dysfunction.

The speakers included Sally Greenberg of the National Consumers League, who noted that women seeking treatment today frequently turn to the Internet for "what amounts to snake oil." The choices are costly, ineffective and "downright dangerous," she added. Others discussed their personal struggles with weakened marriages and constant anxiety, asking the FDA to provide at least one approved therapy.

Cindy Pearson, executive director of the National Women's Health Network, came out against an approval. When it comes to proving efficacy and safety, she said, "Sprout has fallen short on all of these things." Data on clinical meaningfulness "is light," she said. And she recommended that the FDA keep the drug off the market without further studies.

The company also came under fire for its links to Slate Pharmaceuticals, which was cited by regulators 5 years ago for a misleading advertising campaign for Testopel, a testosterone therapy marketed to improve muscle mass and sexual desire. Cindy Whitehead, the CEO at Sprout, was head of operations at Slate, which was sold in 2011.

"It isn't ready for prime time," summed up Sid Wolfe, founder and senior adviser of Public Citizen's Health Research Group and a frequent pharma critic, and will trigger hundreds of cases of syncope (fainting) as well as deaths.

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