Sprout Pharmaceuticals' twice-rejected pill for female sexual desire is coming up for review by a panel of FDA advisers, and the company will likely face questions of whether the drug's benefits outweigh substantial risks.
The drug, flibanserin, is a pill designed to help premenopausal women diagnosed with hypoactive sexual desire disorder (HSDD) regain their sex drives by boosting dopamine and norepinephrine levels in the brain. In briefing documents posted ahead of a Thursday panel meeting, FDA staff acknowledged a consistent if modest HSDD benefit across flibanserin's three Phase III trials but noted that a litany of safety concerns, including risks of fainting and symptoms of depression, could render the drug unapprovable.
Now Sprout will go before a joint meeting of the FDA's reproductive and drug safety panels to make its case. The two committees will vote on whether to approve flibanserin, handing up a nonbinding vote that is commonly followed by the FDA.
The latest panel briefing documents echo what has for years been the rap on flibanserin, a drug that has repeatedly come through with positive efficacy results but been dogged by troubling side effects. At the same time, the complete absence of FDA-approved treatments for female sexual dysfunction--in contrast to the more than 20 libido drugs approved for men--has turned Sprout's candidate into a rallying cry for groups alleging that gender bias is to blame for that disparity.
The FDA, for its part, has firmly denied any such double standard, saying its to-date reticence to approve flibanserin or any similar drug can be explained simply: None of them works very well.
Flibanserin, invented by Boehringer Ingelheim, endured its first rejection in 2010 after failing to significantly beat out placebo in increasing patient-reported sexual desire, tracked with a daily electronic diary, across two Phase III trials. The drug did chart a statistically significant improvement in desire as measured by the Female Sexual Function Index (FSFI), but the FDA and its advisers made clear their preference for the diary method.
Sprout then picked up where Boehringer left off, running a Phase III trial of its own with co-primary endpoints of FSFI improvement and an increase in patient-reported satisfying sexual encounters, or SSEs. The study met its goals, but the positive effects were "modest," the FDA said at the time, and that, coupled with the agency's skepticism about FSFI and a bevy of safety issues, led to the drug's second rejection.
Now, after completing three new Phase I studies designed to address concerns about flibanserin's interaction with other drugs and its effect on patients' ability to drive the morning after use, Sprout believes it's finally in line for approval.
The company plans to market its treatment as Addyi.
- read the briefing (PDF)