LUNESTA(TM) Data Presented at American College of Rheumatology Annual Scientific Meeting; Pilot Study Shows Improvement for Insomnia Patients With Co-Existing Rheumatoid Arthritis

Sepracor Inc. (Nasdaq: SEPR) today announced the presentation of results from its Phase IIIB/IV, 153-patient, four-week, randomized, double-blind, placebo-controlled pilot study evaluating the safety and efficacy of LUNESTA(TM) brand eszopiclone for the treatment of insomnia in patients suffering from rheumatoid arthritis (RA). The results will be presented today at the American College of Rheumatology annual meeting in San Diego.

In this study, nightly use of LUNESTA 3 mg resulted in statistically significant improvement from baseline compared with placebo in patient-reported measures of sleep latency (onset of sleep; p less than or equal to 0.01), wake time after sleep onset (WASO, a sleep maintenance measurement of the amount of time spent awake after initially falling asleep; p less than or equal to 0.01), total sleep time (p less than or equal to 0.05) and sleep quality (p less than or equal to 0.01), for each week of the four-week study. Compared to placebo, patients administered LUNESTA also reported improvements in sleep quality (p<0.0001), feeling refreshed/rested (p=0.001), daytime fatigue (p=0.0002) and relationship enjoyment (p=0.019) as measured by the Insomnia Severity Index at Week 4.

Assessments of RA symptoms with a number of instruments were also conducted in this study. Compared to baseline, patients administered LUNESTA reported improvement in the Arthritis Self-Efficacy Scale (overall score: p=0.046; pain: p=0.006; pain and other symptoms: p=0.019), in the American College of Rheumatology RA Joint Assessment (tender joint count, p=0.035), and in two items of the SF-36 Acute Health Survey (a health survey assessing quality-of-life measures), bodily pain item (p=0.011) and role-physical (p=0.033) at Week 4 versus those patients administered placebo. LUNESTA was generally well tolerated over the treatment period.

“We recognize that sleep problems can co-exist in patients with rheumatoid arthritis and may contribute to the perception of pain and other daytime complaints,” said Mark H.N. Corrigan, M.D., Executive Vice President, Research and Development at Sepracor. “This study, which is part of our Phase IIIB/IV LUNESTA program designed to investigate the effects of LUNESTA on insomnia associated with underlying medical conditions, demonstrated the efficacy and safety of LUNESTA in patients with insomnia and pain associated with rheumatoid arthritis and explored the added benefit of daytime improvements.”

Rheumatoid arthritis is a chronic, systemic disease, mainly characterized by inflammation of the lining of the joints. RA can lead to long-term joint damage, resulting in chronic pain, loss of function and disability, which can in turn lead to difficulty sleeping. According to the Centers for Disease Control and Prevention, an estimated 70 million Americans suffer from arthritis or chronic joint problems. According to a Gallup Poll Survey, 30 percent of all nighttime pain sufferers experience arthritis pain at night. The number rises to 60 percent for those over the age of 50.(1)

LUNESTA is a non-narcotic non-benzodiazepine indicated for the treatment of insomnia in patients who experience difficulty falling asleep as well as for the treatment of patients who have difficulty sleeping through the night (sleep maintenance difficulty). LUNESTA is approved for long-term use. LUNESTA 1 mg, 2 mg and 3 mg tablets are available by prescription in pharmacies nationwide.

An estimated 100 million adult Americans suffer from either chronic or occasional insomnia.(2) Symptoms of insomnia include difficulty falling asleep, awakening frequently during the night, waking up too early, an inability to fall back to sleep or awakening feeling unrefreshed.

The U.S. market for prescription sleep products was approximately $2.1 billion in 2004, excluding products not indicated for the treatment of insomnia that are nonetheless used in its treatment. This represents nearly a 19 percent increase over the previous year, according to IMS Health information.

Important Safety Information

LUNESTA works quickly and should only be taken immediately before bedtime. Be sure you have at least eight hours to devote to sleep before becoming active. You should not engage in any activity after taking LUNESTA that requires complete alertness, such as driving a car or operating machinery. You should use extreme care when engaging in these activities the morning after taking LUNESTA. Do not use alcohol while taking any sleep medicine. Most sleep medicines carry some risk of dependency. Do not use sleep medicines for extended periods without first talking to your doctor. Side effects may include unpleasant taste, headache, drowsiness and dizziness.

Please visit www.sepracor.com or www.lunesta.com to access the FDA-approved labeling text for LUNESTA.

About Sepracor

Sepracor Inc. is a research-based pharmaceutical company dedicated to treating and preventing human disease through the discovery, development and commercialization of innovative pharmaceutical products that are directed toward serving unmet medical needs. Sepracor’s drug development program has yielded an extensive portfolio of pharmaceutical compound candidates with a focus on respiratory and central nervous system disorders. The company’s commercialization efforts are carried out by its U.S.-based, primary care and specialty-oriented sales force, which is comprised of more than 1,400 sales professionals. Sepracor’s corporate headquarters are located in Marlborough, Massachusetts.

This news release contains forward-looking statements that involve risks and uncertainties, including statements with respect to the safety, efficacy and potential benefits of LUNESTA. Among the factors that could cause actual results to differ materially from those indicated by such forward-looking statements are: the results of further clinical trials; the timing and success of submission, acceptance and approval of any additional regulatory filings; changes to LUNESTA product labeling; concerns of LUNESTA prescribers or patients; and certain other factors that are detailed in the company’s quarterly report on Form 10-Q for the quarter ended September 30, 2005 filed with the Securities and Exchange Commission.

In addition, the statements in this press release represent Sepracor’s expectations and beliefs as of the date of this press release. Sepracor anticipates that subsequent events and developments may cause these expectations and beliefs to change. However, while Sepracor may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing Sepracor’s expectations or beliefs as of any date subsequent to the date of this press release.

LUNESTA is a trademark of Sepracor Inc.

(1) National Sleep Foundation. Gallup Poll on adult public’s experiences with nighttime pain. Washington, DC: National Sleep Foundation; 1996.

(2) Extrapolated to current population from 2000 census based on Ancoli-Israel et al. SLEEP. 1999;22 (suppl 2):S347-S353.

For a copy of this release or any recent release, visit www.sepracor.com.