The odds on Boehringer Ingelheim getting a recommendation for approval for flibanserin have lengthened if documents released ahead of a US regulatory panel meeting on Friday are anything to go by.

Papers have been published on the website of the US Food and Drug Administration ahead of a meeting of its Reproductive Health Drugs Advisory Committee on June 18, which will evaluate flibanserin for the treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women. The drug has been dubbed ‘female Viagra’ in some quarters but staffers at the FDA do not seem impressed.

They say in the online-posted review that flibanserin “failed to demonstrate a statistically significant improvement” in sexual desire in two trials. Furthermore they are concerned about side effects possibly linking the drug to appendicitis, depression and loss of consciousness. Some 15% of women halted treatment as a result of adverse events, the staffers argue.

Flibanserin, an oral treatment that was originally developed as an antidepressant, affects levels of serotonin and other chemicals in the brain. How it affects sex drive remains unclear and this is one of the difficulties facing HSDD diagnosis and treatment as a whole, especially when compared to erectile dysfunction where the physical problem is a pretty clear, chemically-treatable one.

Boehringer is confident about its prospects however, and last month unveiled data involving 1,378 pre-menopausal women with HSDD who were evaluated about "bothersome decreased sexual desire" using a seven-point scale from 1 (very much improved) through 4 (no change) to 7 (very much worse). After 24 weeks, 48.3% of women receiving flibanserin and 30.3% on placebo reported feeling very much improved, much improved or minimally improved . In addition, more women on flibanserin reported experiencing a meaningful benefit from the study medication (40.5% versus 25.2%).