Some three years after regulators in the USA rejected flibanserin, Sprout Pharmaceuticals has resubmitted the female sexual dysfunction drug acquired from Boehringer Ingelheim to the Food and Drug Administration.

In June 2010, the agency's Reproductive Health Drugs Advisory Committee voted 10-1 that flibanserin is not effective in increasing female libido and unanimously ruled that its potential side effects, such as loss of consciousness and depression, were not acceptable. Boehringer discontinued development of the compound a few months later but then sold it to Sprout in 2011.

Now the Raleigh, North Carolina company has confirmed that it resubmitted flibanserin for hypoactive sexual desire disorder in pre-menopausal women earlier this year and expects FDA action before the end of 2013. Sprout's announcement comes in connection with the recent publication of positive results of a Phase III trial involving 1,100 women (mean age 36.6 years) in the Journal of Sexual Medicine.

Increase in sexual desire

The study authors concluded that flibanserin resulted in statistically significant improvements in the number of satisfying sexual events, as well as increase in sexual desire when compared with placebo. Flibanserin was further associated with significant reductions in distress associated with low desire, a hallmark of HSDD.

The drug was well tolerated during patients' 24 weeks of use and the most frequently reported adverse events in the flibanserin group were somnolence, dizziness and nausea. However, 9.6% of women receiving flibanserin discontinued due to adverse events versus 3.7% on placebo.

Sprout cited Sheryl Kingsberg, chief of behavioural medicine at the University Hospitals Case Medical Center as saying that "in cases where there is a bio-chemical component to sexual dysfunction, women, unlike men, have no biopharmaceutical options". She added that "the consistency of flibanserin's statistically significant effect on satisfying sexual events and desire, while decreasing the distress of women experiencing HSDD, is very encouraging".

Cindy Whitehead, chief operating officer at Sprout, said this additional data, which is a key part of the resubmission "is responsive to feedback received from FDA previously". She added that "with this study, and other information included in our resubmission, Sprout believes that it has addressed the concerns raised by the FDA during its previous review".

There are no FDA-approved products to treat HSDD and many observers believe Sprout will have a tough time persuading the regulator. At the end of 2011, BioSante Pharmaceuticals' LibiGel (testosterone gel) failed in Phase III trials HSDD in postmenopausal women.