Cephalon's bid to get its sleep drug Nuvigil approved as a treatment for jet lag has been delayed after regulators cast doubt on whether the data proferred by the company was robust enough.

The company has received a complete response letter from the US Food and Drug Administration for its supplemental New Drug Application for Nuvigil (armodafinil) for patients with excessive sleepiness associated with jet lag disorder. The sNDA deals specifically with jet lag suffered while travelling eastbound from the USA.

Cephalon says it “worked closely with the FDA to design a special protocol assessment” that would evaluate the experience of a typical eastbound airline traveller. Patients taking Nuvigil showed a statistically significant improvement over placebo using an objective measure – the Multiple Sleep Latency Test – and a subjective assessment – the Patient Global Impression of Severity (PGI-S).

The most common adverse events associated with treatment (5% or greater) were headache, nausea, insomnia, diarrhoea and palpitations, but the company insists there were no reports of serious rash observed in the trial participants, and no new safety signals were observed. However it seems the FDA is less than impressed with the subjective testing used.

Cephalon chief medical officer Lesley Russell said that “although we reached statistical significance on both primary endpoints, the complete response letter raised questions regarding the robustness of the PGI-S data". She added that “we have already reviewed this issue with the FDA and will be scheduling a meeting with the agency in the near future to discuss it further”.

Nuvigil, which is a long-acting follow-up to Cephalon's Provigil (modanafil), is indicated to improve wakefulness in patients with excessive sleepiness associated with treated obstructive sleep apnea, shift work disorder or narcolepsy. It brought in sales of $35.6 million last year.