The USA’s Endo Pharmaceuticals and its UK partner Vernalis have received disappointing news from US healthcare regulators concerning a bid to get an additional approval for their migraine treatment Frova.

The US Food and Drug Administration has requested an extension of the August 19, review date in order to have more time to look at the supplemental New Drug Application for Frova (frovatriptan) 2.5mg tablets for the additional indication as short-term (six days) prevention of menstrual migraine.

The FDA says that it will provide a revised timeline to Endo and Vernalis, and the companies say they will make an announcement when appropriate. They stressed that the agency has not currently requested any additional information or clinical trial data but investors are worried.

Vernalis shares at 10am this morning were down nearly 3.8% at £0.46 because this delay to the Frova review is the second time this has happened. The original date was May 19 and the lack of urgency coming from the FDA is causing some concern.