Third time’s the charm as Flibanserin is approved by the FDA

As of the 18th August 2015, flibanserin, a non-hormonal drug that treats female sexual interest/arousal disorder (FSIAD) in premenopausal women, has finally been approved by the US Food and Drug Administration (FDA). The advisory committee for the FDA voted 18 to 6 in favour of flibanserin. However, its journey to approval has not been smooth, having previously been rejected twice back in 2010 and 2013. So what had changed? The answer is unclear, and it is controversial as to whether the data or the mass PR campaign funded by Sprout Pharmaceuticals, the developers, played the bigger role.

Proposes that an individuals sexual responsiveness is influenced by the net effect of excitation and inhibition.

Dual Control Model: Proposes that an individual’s sexual responsiveness is influenced by the net effect of excitation and inhibition signals within the brain. (DOI: 10.1111/j.1527-3458.2002.tb00219.x)

Dubbed the “Female Viagra”, flibanserin, is a little pink tablet that is taken once daily at nighttime and claims to improve sexual drive in women. Despite its name, its mechanism of action (MOA) is not similar to viagra, which is taken by men who suffer from erectile dysfunction. Flibanserin, which acts as both an agonist and antagonist, mainly binds to the serotonin 5-HT1A (agonist) and 5-HT2A receptors (antagonist) as well as weakly to the dopamine D4 receptor (agonist). Although its exact MOA is unknown, it is proposed to act under the Kinsey Dual Control model, whereby sexual arousal at any given time is determined by the balance of excitatory (dopamine) and inhibitory (serotonin) signals. Knowing this, flibanserin is thought to correct the imbalance of neurotransmitters by decreasing serotonin and increasing dopamine levels.

So why the controversy? It is thought the FDA might have been bullied into approving the drug by the Sprout Pharmaceutical funded campaign, ‘Even the Score’. The campaigns underlying principle was to argue for gender equality, as there is currently no drug on the market that treats female sexual dysfunction. With an increasing number of campaigns against gender inequality today, this was an ideal moment for the rise of ‘Even the Score’. According to the NY Times, flibanserin supporters flocked in numbers to the advisory committee meeting, reminiscent of a scene from the film ‘Down To Earth’ when Chris Rock and his fellow supporters storm the committee meeting to successfully overrule the decision to demolish a local hospital. Despite being an issue that must be addressed, FDA drug approval needs to be as a result of scientific data and not because of a PR campaign. The FDA strongly refute these accusations, as viagra does not treat lack of sexual desire, therefore flibanserin is the first of its kind. If that was the case then why did they change their mind? The two previous denials were due to its lack of efficacy and its safety issues. The clinical trial data indicated that those receiving flibanserin did not differ from those who had taken placebo pills. The undesirable side effects, the most worrying being hypotension and syncope, are heightened when combined with alcohol consumption or fluconazole containing medicines, such as birth control pills. As flibanserin is most likely to be taken by younger women, this may prove to be problematic. With this in mind, Sprout Pharmaceuticals conducted additional studies. Using differing analytical techniques, both groups of women were required to record the number of sexual satisfying events (SSE), score their sexual desire on a desired scale of 1.2-6.0 and distress on a scale of 0-4. Only one study reported a minor mean increase of 0.4  for sexual desire over placebo patients, but using an analytical technique that the FDA were previously not in complete agreement with when assessing sexual desire. Additionally an average increase of 0.5 SSE/month over the placebo patients were recorded, along with a 0.3 decrease in the distress score. Hardly concrete results any scientist would like to see.

Thus the fundamental question is whether these modest improvements over the placebo group outweigh the risks that accompany flibanserin to warrant an approval. The advisory panel had thought so, but the scientific community seem split. Despite these results, the FDA have been keen to tackle the problems related to sexual dysfunction in women for a long time now. Although flibanserin does not have the most eye catching results, perhaps this is a stepping stone towards an ideal drug.

http://www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/Drugs/DrugSafetyandRiskManagementAdvisoryCommittee/UCM449088.pdf

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Douglas Imrie

Douglas Imrie

I enjoy reading about how our relationship with microbiota affects us on so many levels

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