Sanofi-aventis announced today that the US Food and Drug Administration (FDA) has issued a complete response letter regarding the company's New Drug Application (NDA) for eplivanserin (Ciltyri). Eplivanserin was reviewed as a potential treatment for patients with chronic insomnia characterized by difficulties with sleep maintenance.

Sanofi-aventis is currently reviewing the content of the complete response letter, in which the FDA has requested additional information regarding benefit-risk. The company will contact the FDA in the coming days to request a meeting to discuss what steps and data would be needed for approval.

Eplivanserin, discovered and developed by sanofi-aventis, is a serotonin type 2 A receptor antagonist, and unlike benzodiazepine-receptor agonists (BzRAs), has no affinity for GABA receptors. It has been studied in a clinical development programme including nearly 3,000 patients.

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