Somaxon Pharmaceuticals, Inc, San Diego, has completed the genotoxicity studies requested by the FDA for SILENOR™ (doxepin HCl), the company’s lead product candidate for the treatment of insomnia. In accordance with FDA guidance, these studies consisted of an in vitro bacterial reverse mutation test, an in vitro mammalian chromosomal aberration test, and an in vivo rodent micronucleus test to assess for chromosomal damage.

The company, in its assessment of the results, did not observe a signal indicative of genotoxicity in any of the assays. Somaxon plans to shortly submit the data to the FDA and, based on its assessment, request that the agency permit the company to submit the data from the requested carcinogenicity studies of SILENOR™ as a post- New Drug Application (NDA) approval commitment. The FDA has previously indicated to Somaxon that depending on the outcome of the genotoxicity studies, it may be flexible as to the timing of the conduct of the carcinogenicity studies, including the potential that the data from those studies may be submitted post-approval.

The company is also conducting the reproductive toxicology studies of SILENOR™ requested by the FDA and plans to complete those studies in the first half of 2007.