Phase II Clinical Results Announced for Gaboxadol, First in a New Class of Sleep Medicines Known as Selective Extrasynaptic GABA-A Agonists -SEGA-.

DENVER -- Acute Administration of Gaboxadol Significantly Improved Several Key Sleep Measures in Patients with Primary Insomnia

Merck & Co., Inc. and H. Lundbeck A/S announced today, at the 19th Annual Meeting of the Associated Professional Sleep Societies (APSS), results of a Phase II clinical trial with gaboxadol, an investigational agent in Phase III for the treatment of insomnia and the first Selective Extrasynaptic GABA-A Agonist (SEGA), a new class of sleep agents. Gaboxadol demonstrated significant improvement over placebo in several study endpoints for both sleep initiation and sleep maintenance in patients with Primary Insomnia. Gaboxadol 15 mg also significantly increased the amount of slow wave sleep patients experienced. Gaboxadol was generally well tolerated with no observed next-day residual effects in this research trial. Merck and Lundbeck are collaborators in the clinical development and commercialization of gaboxadol.

"The findings of this early stage trial show that gaboxadol significantly improved several measures of sleep initiation and sleep maintenance in patients with Primary Insomnia," said Stephen Deacon, Ph.D., lead investigator of the study and head of Clinical Development, Sleep Disorders, Lundbeck U.K. "Gaboxadol 15 mg significantly reduced Total Time Awake by 16 percent and Latency to Persistent Sleep by 21 percent, compared to placebo. The findings of this Phase II study demonstrate the therapeutic potential of gaboxadol as a treatment for insomnia. It will be important to confirm these findings in larger clinical trials," added Dr. Deacon.

"The mechanism of action for gaboxadol appears to be unique relative to other sleep agents in that it selectively targets the extrasynaptic GABA-A receptors," said Tom Roth, Ph.D., director, Sleep Disorders & Research Center, Henry Ford Hospital, Detroit. "These receptors have a significant presence in areas of the brain thought to be important for sleep regulation."

Study design

This randomized, double-blind, 3-way crossover, placebo-controlled polysomnograph (PSG) study evaluated 26 patients aged 18-65 years diagnosed with Primary Insomnia (DSM-IV criteria) to assess the acute efficacy and safety of gaboxadol. Patients were administered gaboxadol 5 mg, 15 mg or placebo 30 minutes before bedtime on two consecutive nights during three sessions separated by seven to 14 days.

Baseline PSG measures confirmed that patients had difficulty in falling and remaining asleep. Patients evaluated their subjective sleep quality using the Leeds Sleep Evaluation Questionnaire. Next-day residual effects were assessed using the Cognitive Drug Research (CDR) test battery.

Study results

The efficacy analyses were based on the average of nights one and two and are presented as group means. Compared with placebo, gaboxadol 5 mg and 15 mg significantly reduced Total Time Awake by 15 percent and 16 percent, respectively (5 mg: 58.2 minutes, 15 mg: 57.3 minutes, placebo: 68.5 minutes, p less than 0.05) and improved Total Sleep Time by 3 percent (5 mg: 419.8 minutes, p less than 0.05; 15 mg: 420.3 minutes, p less than 0.01; placebo: 408.7 minutes). Additionally, compared with placebo, gaboxadol 15 mg significantly reduced Latency to Persistent Sleep by 21 percent (15 mg: 23.6 minutes, placebo: 30 minutes, p less than 0.05) and increased by 21 percent the amount of time patients spent in Slow Wave Sleep (15 mg: 114 minutes, placebo: 93.9 minutes, p less than 0.001).

In this small investigational study, no statistically significant treatment effect was observed on wakefulness during sleep or number of awakenings, although both doses reduced wakefulness during sleep on the first night of treatment.

Patients treated with gaboxadol showed no next-day residual effects based on the CDR test battery. Gaboxadol was generally well tolerated at both doses. Adverse events in the study were mild or moderate and included abdominal pain, somnolence, dizziness and headache.

Additional larger studies are underway to confirm these early findings and to further assess the efficacy and safety profiles of gaboxadol.

About gaboxadol

Gaboxadol is a novel compound currently in phase III development for the treatment of insomnia. Gaboxadol appears to interact directly with the extrasynaptic GABA receptor recognition site and mediates its effects via a GABA-A receptor population that is different from that modulated by benzodiazepine receptor agonists.

About insomnia

Insomnia is defined by complaints of inadequate or poor-quality sleep, generally including difficulty falling asleep, waking up frequently during the night with difficulty returning to sleep, and/or experiencing unrefreshing sleep. It is estimated that insomnia affects more than 70 million Americans at some time in their lives.

About Merck

Merck & Co., Inc. is a global research-driven pharmaceutical company dedicated to putting patients first. Established in 1891, Merck discovers, develops, manufactures and markets vaccines and medicines in more than 20 therapeutic categories. The company devotes extensive efforts to increase access to medicines through far-reaching programs that not only donate Merck medicines but help deliver them to the people who need them. Merck also publishes unbiased health information as a not-for-profit service. For more information, visit www.merck.com.

About H. Lundbeck A/S

H. Lundbeck A/S is an international pharmaceutical company engaged in the research and development, production, marketing and sale of drugs for the treatment of psychiatric and neurological disorders. In 2004, the company's revenue was DKK 9.7 billion. The number of employees is approximately 5,000. For more information, visit www.lundbeck.com.

Merck Forward-Looking Statement 

This press release contains "forward-looking statements" as that term is defined in the Private Securities Litigation Reform Act of 1995. These statements involve risks and uncertainties, which may cause results to differ materially from those set forth in the statements. The forward-looking statements may include statements regarding product development, product potential or financial performance. No forward-looking statement can be guaranteed, and actual results may differ materially from those projected. Merck undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events, or otherwise. Forward-looking statements in this press release should be evaluated together with the many uncertainties that affect Merck's business, particularly those mentioned in the cautionary statements in Item 1 of Merck's Form 10-K for the year ended Dec. 31, 2004, and in its periodic reports on Form 10-Q and Form 8-K, which the company incorporates by reference.

H. Lundbeck A/S Forward-Looking Statement

The content of this release will have no influence on the Lundbeck Group's expectations for the financial result for 2005.