Results of the primary endpoint for this trial, eight-hour wake after sleep onset (WASO), which is an objective measure of sleep maintenance using polysomnography in a sleep laboratory setting, were significant for both doses. Silenor (doxepin HCl) demonstrated improvement in mean WASO of 26 minutes for 3mg and 31 minutes for 6mg versus placebo for the primary analysis. Statistical significance versus placebo was maintained at both doses for all time points.
Improvement on total sleep time (TST) was statistically significant for both doses at the initial treatment period, increasing from 374 minutes for placebo to 415 minutes for Silenor 3mg and 421 minutes for Silenor 6mg. After four weeks of nightly administration, improvement in TST remained statistically significant for both doses relative to placebo.
Both doses of Silenor also demonstrated statistically significant improvements in sleep efficiency versus placebo, and a statistically significant reduction in latency to persistent sleep at the initial treatment period.
In addition, both doses of Silenor were well tolerated. Side effects in the Silenor groups were comparable to placebo and there were no statistically significant differences versus placebo in next day residual measures. There was no evidence of tolerance to Silenor over the treatment period and sleep architecture was preserved. Rebound insomnia, withdrawal effects, memory impairment, weight gain and anticholinergic effects were not observed.
“We are very encouraged by these results,” remarked Ken Cohen, Somaxon’s president and CEO. “We are undertaking a comprehensive phase III program that has the potential, if successful, to establish Silenor as a first line treatment for patients with insomnia. Results from the clinical trial, coupled with the mechanism of action which is distinct from benzodiazepine and non-benzodiazepine products for insomnia, creates an opportunity for differentiation in the market.”
The company anticipates reporting results from the remaining phase III trials of Silenor later this year, with a new drug application (NDA) filing targeted for Q1 2007.