After a long and financially consuming process for Somaxon Pharmaceuticals, the US Food and Drug Administration (FDA) has approved the company’s New Drug Application (NDA) for [removed]Silenor[/removed] (doxepin) for the treatment of insomnia characterized by difficulty with sleep maintenance.

Sleep maintenance difficulty, defined as waking frequently during the night and/or waking too early and being unable to return to sleep, is the most commonly reported nighttime symptom of insomnia. Silenor is approved for the treatment of both transient (short term) and chronic (long term) insomnia characterized by difficulty with sleep maintenance in both adults and elderly patients. In clinical trials, Silenor demonstrated maintenance of sleep into the 7th and 8th hours of the night, with no meaningful evidence of next day residual effects.

Silenor has not been designated as a controlled substance by the US Drug Enforcement Administration because of its demonstrated lack of abuse potential. In addition, in the Silenor clinical development program, no withdrawal effects or other adverse events were observed that were indicative of physical dependence, a statement from the company says. In Somaxon’s market research, abuse potential/risk of dependence was one of the most common safety concerns cited by patients as a reason for not seeking prescription treatment for insomnia, switching medications, or discontinuing treatment. The Silenor clinical trial program demonstrated a favorable safety and tolerability profile, with the overall incidence of adverse events comparable to placebo, a low discontinuation rate, and no evidence of tolerance, amnesia, or complex sleep behaviors (eg, sleep driving, sleep eating).

"The approval of Silenor represents an important milestone for Somaxon and will allow us to provide physicians and patients with a highly differentiated treatment option for insomnia," said Richard W. Pascoe, Somaxon’s president and CEO. "We believe that Silenor’s ability to treat sleep maintenance insomnia into the final hours of the night without meaningful next-day residual effects and without abuse potential uniquely positions Silenor for commercial success."

Now, the company will focus on seeking a US commercial partnership.

"Looking forward, we will continue to execute on our business strategy, focusing on seeking a US commercial partnership, building a US commercial presence, and preparing to launch Silenor in the second half of 2010," continued Pascoe.

"The management of insomnia has important implications for the patient’s overall health, productivity, and quality of life," said Thomas Roth, PhD, chief, division head, Sleep Disorders & Research Center, Henry Ford Hospital. "The introduction of Silenor, a sleep promoting medication that works through the histamine system, provides the clinician an important addition to his armamentarium needed for the management of insomnia patients."

Silenor binds with high affinity to histamine (H1) receptors. This is believed to be the mechanism by which Silenor promotes the maintenance of sleep. This mechanism of action is different from that of any other prescription medication currently approved for the treatment of insomnia.

As result of the NDA approval for Silenor, Somaxon will be required to make a $1 million milestone payment to its licensor for Silenor pursuant to its existing license agreement.