US regulators have approved Sprout Pharmaceuticals' flibanserin for hypoactive sexual desire disorder in premenopausal women. Regulators previously rejected the controversial drug twice, and the change in decision prompted critics to raise concern that the approval was a triumph of marketing over science.

Flibanserin is a serotonin receptor 1A agonist and a serotonin receptor 2A antagonist that was initially developed as an antidepressant. Its mechanism of action in hypoactive sexual desire disorder is unknown. In three randomized trials of the drug in a total of 2,400 premenopausal women, the drug increased the number of satisfying sexual events by 0.5–1 events per month over placebo. It also increased sexual desire on average by 0.3–0.4 points (on a 3-point scale) over placebo. Adverse events included low blood pressure and loss of consciousness, especially in women who drank alcohol.

The drug, developed and first filed by Boehringer Ingelheim, was initially rejected on the basis of results from two pivotal trials in 2010. At that time, a US Food and Drug Administration (FDA) advisory panel voted unanimously that the drug's side effects were unacceptable and voted 10 to 1 that the data did not demonstrate efficacy. Boehringer discontinued development of the drug after the rejection, and sold it to Sprout Pharmaceuticals in 2011. Sprout resubmitted the drug in 2013, with data from a third pivotal trial, only to have it rejected again that year.

Sprout resubmitted the drug this year with additional safety data. At an FDA advisory meeting in June, independent experts voted 18 to 6 to approve the drug with a risk evaluation and mitigation strategy (REMS). This vote and the approval a few months later led some critics to note that marketing tactics — including an effort by 'Even The Score', a Sprout-funded advocacy group, to portray the previous rejections as a 'gender equality issue' at the FDA — swayed the decision.

“The Even the Score advocacy campaign, the shifting efficacy end points and use of a patient-reported outcome measure, the tenuous risk–benefit balance among the studied population and potential for widespread off-label use, and an unmet medical need [...] are not totally unfamiliar territory for the FDA, but represent a challenge when they occur simultaneously,” wrote three of the FDA's independent advisors after the approval (JAMA 314, 869–870; 2015). “What makes the approval process for flibanserin even more unique is the politically charged atmosphere in which the FDA will decide how all these trade-offs should best be navigated.”

Days after the approval, Valeant bought Sprout for US$1 billion.