SEPRACOR REPORTS 2ND QTR 2005 NET LOSS OF $7.4 MILLION.

The MDI development program included approximately 1,870 pediatric and adult subjects and 54 studies (preclinical and clinical). In each of the three, large-scale, pivotal Phase III trials that Sepracor conducted, the XOPENEX HFA MDI was well tolerated and met the targeted efficacy endpoints in both adults and children with asthma. In the primary airway function measure, FEV(1) (a test of lung function that measures the amount of air forcefully exhaled in one second), the XOPENEX HFA MDI produced statistically (p<0.001) and clinically significant improvements relative to placebo. Approximately 96 percent of the short-acting beta-agonist inhalers sold in 2004 contained chlorofluorocarbon (CFC) propellants, according to IMS Health information. Under provisions in the Montreal Protocol on Substances that Deplete the Ozone Layer, an international agreement that requires the phase-out of substances that deplete the ozone layer, MDIs containing CFC propellants would qualify for removal from the marketplace. In March 2005, the FDA issued its final rule for the removal of the essential use exemption for albuterol, which currently permits the use of CFC-containing albuterol inhalers despite environmental concerns. Under the rule, all production and sales of albuterol CFC MDIs in the U.S. must cease by the end of 2008. The XOPENEX MDI uses HFA technology and does not contain a CFC propellant.

Currently, the U.S. short-acting bronchodilator MDI market potential at branded prices, assuming parity pricing to branded PROVENTIL(R) HFA, is approximately $1.8 billion.

NDA-Preparation Program

Arformoterol - Sepracor has completed more than 100 preclinical studies and 16 clinical studies for arformoterol inhalation solution as a maintenance treatment for COPD. In 2004, Sepracor completed Phase III studies for arformoterol in which patients treated with arformoterol demonstrated a significant improvement in FEV(1) after dosing with a duration of action of up to 24 hours, versus those taking placebo. Sepracor is currently preparing the arformoterol NDA and is targeting submission of the NDA to the FDA in the fourth quarter of 2005.

Bronchodilators have the potential to improve lung function, decrease symptoms, help increase mucus clearance and reduce the number of exacerbations in patients suffering from COPD. The U.S. market for long-acting bronchodilators, including the combination product ADVAIR(R), was approximately $4.2 billion in 2004, according to IMS Health information.

Sepracor's Phase II Programs and Additional Clinical Candidates

SEP-226330 - SEP-226330 is a norepinephrine and dopamine reuptake inhibitor (NDRI). Sepracor initiated a Phase II study of SEP-226330 for the treatment of restless legs syndrome in the fourth quarter of 2004. This compound may have advantages over currently used dopamine agonists in the treatment of restless legs syndrome, which is a movement disorder that is reported to afflict approximately 16 percent of the U.S. adult population.(b) Sepracor is also conducting preclinical evaluations of SEP-226330 as a potential novel mechanistic approach for the treatment of Parkinson's disease. (S)-Amlodipine - Sepracor has conducted both Phase I and Phase II studies of (S)-amlodipine for the treatment of hypertension. Amlodipine, marketed by Pfizer Inc. as NORVASC(R), is the leading calcium channel antagonist approved for use for the treatment of hypertension and angina. The evolving paradigms for hypertension treatment are focusing on the use of multiple mechanistic approaches as initial therapy, such as the use of calcium channel blockers (CCBs) with angiotensin converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs).

SEP-225289 - Sepracor plans to submit an Investigational New Drug (IND) application to the FDA and begin a Phase I clinical study for SEP-225289, a norepinephrine, dopamine and serotonin reuptake inhibitor, for the treatment of depression, in 2005. According to the National Institutes of Mental Health, in a given year, approximately 18.8 million Americans have a depressive disorder.

SEP-227162 - SEP-227162 is a serotonin and norepinephrine reuptake inhibitor that Sepracor plans to investigate for the treatment of depression. Other dual reuptake inhibitors have been shown in studies to be successful in the treatment of depression.

Important Safety Information - LUNESTA

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. All 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. For more product information or for the full prescribing information, please refer to the Sepracor web site at www.sepracor.com.

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, 1,250-person, primary care and specialty-oriented sales force. Sepracor's corporate headquarters are located in Marlborough, Massachusetts. Forward-Looking Statement (a) Extrapolated to current population from 2000 census based on Ancoli-Israel et al. SLEEP. 1999;22 (suppl 2):S347-S353 (b) Data Monitor, October 2004

For more information, visit http://www.sepracor.com or call 508/481-6700.