Sepracor Inc announced that the US FDA has accepted the resubmission of the New Drug Application (NDA) for Estorra brand eszopiclone for the treatment of insomnia as a complete response and has begun its review of the resubmission. The FDA has classified the resubmission as Class 2.

Under the Prescription Drug User Fee Act (PDUFA), FDA review of a Class 2 resubmission is expected to be completed within a six-month period beginning on the date that the resubmission was received. The Class 2 designation is consistent with Sepracor's previously announced expectations regarding the timeframe for the FDA review of the resubmission, a company release says.

Resubmission of an NDA after receipt of an approvable letter is intended to answer all of the questions that need to be addressed prior to approval of the NDA.

On February 27, 2004, Sepracor received an "approvable" letter from the FDA for its NDA for Estorra for the treatment of insomnia characterized by difficulty falling asleep and/or difficulty maintaining sleep during the night and early morning. Contingent upon approval from the FDA of the Estorra NDA, Sepracor would expect the recommended dosing to achieve sleep onset and maintenance to be 2 mg and 3 mg for adult patients, 2 mg for elderly patients with sleep maintenance difficulties, and 1 mg for sleep onset in elderly patients whose primary complaint is difficulty falling asleep. The FDA has not requested additional clinical or preclinical trials for approval.

The NDA contains a total of 24 clinical trials, which included more than 2,700 adult and elderly subjects, and more than 60 preclinical studies. A total of six randomized, placebo-controlled Phase III studies for the treatment of chronic or transient insomnia were conducted in both adult and elderly patients and were part of the NDA package, the release continues.

The US market for prescription sleep products, not including off-label use of central nervous system agents not indicated for the treatment of insomnia, was approximately $1.8 billion in 2003.

According to the National Institutes of Health web site, insomnia affects more than 50 million Americans. Symptoms of insomnia include difficulty falling asleep, awakening frequently during the night, waking up too early, an inability to fall back to sleep, or awakening feeling un-refreshed.