US regulators have told Sanofi-Aventis that it needs to provide more information before the company's investigational insomnia treatment, eplivanserin, can be given the green light.

The US Food and Drug Administration has issued a complete response letter regarding Ciltyri (eplivanserin) which was reviewed as a potential treatment for patients with chronic insomnia characterised by difficulties with sleep maintenance. The French drugmaker, which said that it is currently reviewing the content of the letter, confirmed that the agency has requested additional information “regarding benefit-risk”.

Sanofi added that it will contact the FDA “in the coming days to request a meeting to discuss what steps and data would be needed for approval”. Eplivanserin is a serotonin type 2 A receptor antagonist and has been studied in a clinical programme including nearly 3,000 patients.

The Paris-headquartered firm will be hoping the talks with the FDA go well as it has high hopes for the product. Sanofi has previously said that unlike current hypnotics, eplivanserin is not a sedative and therefore has no after-effects the following morning.

The insomnia treatment market has been dominated in the past by Sanofi’s own Stilnox/Ambien (zolpidem), which is now available generically and other drugs acting on the gama-aminobutyric acid-A receptor.