West Coast Editor

Days after raising $65 million in a Series C financing, Somaxon Pharmaceuticals Inc. is kicking off the first of two Phase III trials with lead product Silenor (doxepin), hoping to prove that the compound's active ingredient - currently prescribed at high doses for depression - also works against insomnia.

The multicenter, placebo-controlled Phase III study will evaluate the safety and efficacy of Silenor in adults with primary, chronic insomnia, using the primary endpoint of wake after sleep onset as measured by polysomnography in a sleep laboratory. Secondary endpoints of sleep maintenance, onset and duration will be measured objectively and through patient-reported outcomes.

Company officials could not be reached for comment on Thursday.

The tricyclic antidepressant doxepin, originally from New York-based Pfizer Inc., is available in generic form and is sold under the brand names Adapin, Sinequan and Zonalon. Some physicians prescribe it off label for fibromyalgia and chronic pain.

The $2 billion-plus potential insomnia market has drawn others to the field. Sepracor Inc., of Marlborough, Mass., received approval in December of Lunesta, and San Diego-based Neurocrine Biosciences Inc. in April resubmitted a new drug application for indiplon to treat insomnia in both adults and the elderly. (See BioWorld Today, Oct. 20, 2004, and Dec. 17, 2004.)

Indiplon is a non-narcotic, non-benzodiazapine agent designed to act on a specific site of the GABA-A receptor. Coincidentally, Somaxon has in-licensed the worldwide rights to the use of acamprosate, a GABA-A agonist and N-methyl-D-aspartate glycine, or NMDA, receptor antagonist, for the treatment of movement disorders and other conditions.

Meanwhile, with Silenor, a second Phase III study is expected to begin later this year, specifically targeting elderly patients - the fast-growing population group most afflicted by insomnia.

Results with Silenor so far have been encouraging. Two Phase II dose-finding trials against primary sleep maintenance insomnia, one in adults and one in elderly patients, yielded statistically significant improvement in sleep maintenance measures such as WASO, as well as sleep duration measures such as total sleep time and sleep induction measures such as latency to sleep onset.

Current insomnia market leader Ambien (zolpidem), from Paris-based Sanofi-Aventis Group, is indicated for sleep onset only, while the recently cleared Lunesta won a label for sleep onset and maintenance. One advantage of Silenor is that, unlike Ambien, it is not classified as a Schedule IV controlled substance, a category assigned when authorities want to better control access because of the possibility of abuse (although Ambien is said to have less potential for abuse than drugs in the benzodiazepine class).

San Diego-based Somaxon earlier this week raised $65 million, saying the firm is aiming to file a new drug application by the end of next year. (See BioWorld Today, June 7, 2005.)