The US Food and Drug Administration (FDA) has given its backing to Transcept Pharmaceutical’s Intermezzo as an effective treatment for insomnia, but has requested additional data to prove its safety.

The complete response letter was issued by the FDA in response to a New Drug Application submitted by Transcept in September 2008 for Intermezzo as a treatment for insomnia, caused when people wake up in the night and experience difficulty getting back to sleep.

In the letter the FDA stated that Transcept had submitted substantial evidence of effectiveness of Intermezzo and recognised that the data did not indicate significant next-day residual effects.

However, the FDA indicated that the intended use of Intermezzo in the middle of the night represents a unique insomnia indication and dosing strategy, for which safety has not been previously established.

The health body has therefore requested additional data to demonstrate the new treatment does not present an unacceptable risk of residual effects, with particular reference to patient dosing errors and next-day driving ability.