Cephalon is facing a delay in securing approval for Nuvigil, its new treatment for excessive sleepiness associated with narcolepsy and other disorders in the USA, after the Food and Drug Administration stopped short of granting full approval for the drug yesterday.

The FDA sent Cephalon an ‘approvable’ letter for Nuvigil (armodafinil) asking for more discussion before it could give the drug a green light. Nuvigil is a follow-up to Cephalon’s already-marketed Provigil (modafinil), its top-selling drug.

Nuvigil is a single-isomer version of modafinil – in other words it is made up of just one of the two mirror-image forms of the active molecule – and is claimed to offer a longer duration of action than the parent product.

Cephalon said the sticking point for the agency at the moment is Nuvigil’s labelling, which has been complicated by the FDA’s review of another product based on modafinil, Sparlon for attention-deficit hyperactivity disorder. Sparlon was recently voted down by an FDA advisory panel on concerns about a child who suffered a serious skin reaction – known as Stevens-Johnson Syndrome – after taking the drug in a clinical trial.

Cephalon has since submitted data to the FDA suggesting that the child was not in fact suffering from SJS, and said the FDA had indicated that it would take this new information into account during the Sparlon review, which will have a bearing on the label for Nuvigil.

The company reported yesterday that its first quarter sales leapt 30% to $346 million, with Provigil advancing 48% to $149 million. Despite the sales hike, net profit fell 86% to $3.6 million, in part because of settlement payments to companies that had threatened to launch generic versions of Provigil and also two product licensing deals.

Cephalon filed for approval to market Nuvigil for excessive sleepiness associated with narcolepsy, obstructive sleep apnea/hypopnea syndrome and shift work sleep disorder on March 31, 2005.