Clinical Data on Somaxon Pharmaceuticals' Product Candidate for the Treatment of Insomnia Presented at American Psychiatric Association Annual Meeting

Business Wire, May 7, 2008

Data Presented from Three Phase 3 Clinical Trials of the Company's Product Candidate SILENOR[TM] (Doxepin HCl) for the Treatment of Insomnia

SAN DIEGO -- Somaxon Pharmaceuticals, Inc. (Nasdaq: SOMX), a specialty pharmaceutical company focused on the in-licensing and development of proprietary product candidates for the treatment of diseases and disorders in the fields of psychiatry and neurology, today announced that data from three Phase 3 clinical trials of the company's product candidate SILENOR[TM] (doxepin HCl) for the treatment of insomnia were presented today at the American Psychiatric Association (APA) 161st annual meeting in Washington, D.C.

The data presented at the APA meeting are a subset of the data from Somaxon's completed Phase 3 development program, which comprised four Phase 3 clinical trials evaluating SILENOR[TM], a low-dose (1-6 mg) formulation of doxepin for the treatment of insomnia. As the company has previously reported, all of these clinical trials demonstrated statistically significant differences relative to placebo for their primary endpoints and multiple secondary endpoints. The clinical trials demonstrated significant and clinically meaningful improvements in sleep onset, sleep maintenance and the prevention of early morning awakenings. In addition, the side effect profile was comparable to placebo, and there were no reports of amnesia, hallucinations or complex sleep behaviors. There were no next-day residual effects found at what are expected to be the recommended starting doses, and there was no apparent evidence of anticholinergic effects (e.g., dry mouth), tolerance, rebound insomnia, withdrawal effects or weight gain as compared to placebo.

"While several prescription products for the treatment of insomnia have become available in recent years, we believe that a need remains for a medication that helps people fall asleep and stay asleep throughout the night without next-day residual effects or risk of dependence," said David F. Hale, Somaxon's executive chairman and interim chief executive officer. "We believe that based on the clinical profile of low-dose doxepin demonstrated by the data presented today at the APA annual meeting and otherwise publicly announced by us, SILENOR[TM] can be an attractive treatment alternative for physicians and the insomnia patients they treat, if it is approved by the FDA."

A summary of the posters presented today at the APA annual meeting is as follows:

Efficacy of Doxepin 3 and 6mg on Early Morning Awakenings in Adults with Primary Insomnia.

A randomized, double-blind, placebo-controlled clinical trial explored the effect of 3 mg and 6 mg of doxepin versus placebo for 35 nights in a total of 229 adults with chronic primary insomnia. Data averaged over the double-blind treatment period was reported. Doxepin 3 mg and 6 mg doses demonstrated statistically significant improvements compared with placebo in wake time after sleep (WTAS), sleep efficiency (SE) in the last quarter of the night and overall SE at hour 8.

Next-day residual effects were assessed using the Digit Symbol Substitution Test (DSST), the Symbol Copying Test (SCT), and a Visual Analog Scale (VAS) for sleepiness. There were no significant group differences in the DSST, SCT, or VAS at any timepoint during the clinical trial. The prevention of early morning awakenings without next-day residual effects in this study is notable, given that this symptom of insomnia is prevalent but seldom addressed in clinical trials.

Long-term Efficacy and Safety of Doxepin 1 and 3mg in Elderly Subjects with Chronic Primary Insomnia.

A randomized, double-blind, placebo-controlled clinical trial assessed the long-term efficacy and safety profile of doxepin among elderly adults with chronic primary insomnia. Doxepin 3mg demonstrated significant improvement on the first night in wake after sleep onset (WASO), total sleep time (TST), overall SE and SE in hour 8, all versus placebo. Improvements were sustained at night 85 for all variables, with significance maintained for WASO, TST, and overall SE. Doxepin 3 mg also significantly improved the interactive voice response system (IVRS) variables latency to sleep onset (LSO), TST and sleep quality.

Significant improvements were observed for doxepin 1 mg for several measures and at several timepoints, including WASO, TST and overall SE.

Several global insomnia outcome parameters were also improved, with both doses demonstrating improvement in patient and clinician-based ratings of therapeutic effectiveness. These improvements were significant throughout the trial at the 3 mg dose and by the end of the trial at the 1 mg dose.

Both doses were well-tolerated, with side effect profiles comparable between groups, no reports of complex sleep behaviors, amnesia or anticholinergic effects and no next-day residual effects.

Efficacy and Safety of Doxepin 6mg in a 4-Week Outpatient Trial of Elderly Subjects with Primary Insomnia.

A four-week, double-blind, placebo-controlled outpatient clinical trial explored the efficacy and safety of doxepin among elderly adults with sleep maintenance insomnia. Doxepin 6 mg demonstrated significant improvements compared with placebo in subjective total sleep time (sTST) and subjective wake after sleep onset (sWASO) at Week 1. These improvements were sustained at Weeks 2, 3 and 4.