Oscient Pharmaceuticals Completes Enrollment in Phase IV Trial of FACTIVE Tablets.

Post-marketing FORCE trial completed ahead of schedule

WALTHAM, Mass. -- Oscient Pharmaceuticals Corporation (Nasdaq: OSCI) has completed enrollment in its Phase IV post-marketing trial for its fluoroquinolone antibiotic, FACTIVE([R]) (gemifloxacin mesylate) tablets. Known as the FORCE trial (FACTIVE Outpatient Respiratory Infection Community Experience), Oscient began enrollment coincident with the launch of FACTIVE in the fall of 2004. A commitment to complete post-marketing trials has become a condition of approval for many drugs and this trial was expected to take three to four years to complete. Patient enrollment at more than 200 clinical sites was completed nearly one year ahead of schedule, which allows for the submission of the study report to the FDA earlier than planned.

"By meeting our commitment to the FDA ahead of schedule, we reduce the total expense of the study and, following submission, our clinical development expenditures will decrease," stated Steven M. Rauscher, President and Chief Executive Officer of Oscient Pharmaceuticals. "With more than one million patients treated worldwide, FACTIVE is an important option for physicians treating serious lower respiratory tract infections."

The prospective, randomized study was designed to examine the safety of FACTIVE in treating community-acquired pneumonia of mild to moderate severity (CAP) versus clarithromycin and in treating acute bacterial exacerbations of chronic bronchitis (AECB) versus amoxicillin/clavulanate in the community. Conducted in physician offices across the U.S., the trial enrolled more than 7,500 patients: approximately 5,000 in the FACTIVE treatment group and approximately 2,500 in the comparator group. The study included patients of different ethnicities to gain additional safety information on populations not substantially represented in the clinical trial program. Preliminary results observed to date are consistent with clinical trial results and pharmacovigilance data for FACTIVE and have been submitted to the FDA through interim analyses. The Company expects to submit the final study report to the FDA later this year.

FACTIVE is approved in the U.S. for the seven-day treatment of CAP and the five-day treatment of AECB. The FDA has established an action date of May 1, 2007 for the Company's supplemental New Drug Application seeking approval for a five-day treatment of CAP.

About Oscient Pharmaceuticals

Oscient Pharmaceuticals Corporation is a commercial-stage biopharmaceutical company marketing two FDA-approved products with its national primary care sales force. ANTARA([R]) (fenofibrate) capsules is indicated for the adjunct treatment of hypercholesterolemia (high blood cholesterol) and hypertriglyceridemia (high triglycerides) in combination with diet. FACTIVE([R]) (gemifloxacin mesylate) tablets is an antibiotic approved for the treatment of acute bacterial exacerbations of chronic bronchitis and community-acquired pneumonia of mild to moderate severity. Oscient also has a novel, late-stage antibiotic candidate, Ramoplanin, under investigation for the treatment of Clostridium difficile-associated disease (CDAD).

For important information regarding the safety and use of ANTARA, please see the full prescribing information available at www.antararx.com.

Important Safety Information about FACTIVE Tablets

The most common (more than 2% incidence) drug-related side effects reported in FACTIVE clinical trials were diarrhea (3.6%), rash (2.8%) and nausea (2.7%). In clinical trials, drug-related rash was reported in 2.8% of patients receiving gemifloxacin and was more commonly observed in patients less than 40 years of age, especially females. The incidence of rash increases with treatment longer than the maximum-labeled duration of 7 days. In clinical trials, the discontinuation rate due to drug-related adverse events was similar for FACTIVE tablets and comparators (2.2% versus 2.1%, respectively).

Gemifloxacin is contraindicated in patients with a history of hypersensitivity to gemifloxacin, fluoroquinolone antibiotic agents, or any of the product components. Patients receiving marketed fluoroquinolones have reported serious and occasionally fatal hypersensitivity and/or anaphylactic reactions, peripheral neuropathy, antibiotic-associated colitis and tendon ruptures. Gemifloxacin should be discontinued immediately at the first sign of any of these events.

Fluoroquinolones may prolong the QT interval in some patients. Gemifloxacin should be avoided in patients with a history of prolongation of the QTc interval, patients with uncorrected electrolyte disorders (hypokalemia or hypomagnesemia), and patients receiving Class IA or Class III antiarrhythmic agents. In clinical studies with gemifloxacin, CNS effects have been reported infrequently. As with other fluoroquinolones, gemifloxacin should be used with caution in patients with known or suspected CNS diseases. If CNS reactions occur, gemifloxacin should be discontinued and appropriate measures instituted.

No significant drug-drug interactions were seen with theophylline, digoxin, oral contraceptives, cimetidine, omeprazole, and warfarin, although patients receiving a fluoroquinolone concomitantly with warfarin should be monitored closely. Drug-drug interactions include probenicid, sucralfate, antacids containing aluminum or magnesium, iron, multivitamins containing metal cations, and didanosine. The safety and effectiveness of gemifloxacin in children, adolescents (less than 18 years of age), pregnant women, and lactating women have not been established. For complete safety and efficacy information, please see the full prescribing information available at www.factive.com.

Forward-Looking Statement

This news release contains forward-looking statements made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, including statements with regard to the expectation that the Company will submit the final study report relating to the FORCE trial to the FDA later this year. Forward-looking statements represent our management's judgment regarding future events. Forward-looking statements typically are identified by use of terms such as "may," "will," "should," "plan," "expect," "intend," "anticipate," "estimate," and similar words, although some forward-looking statements are expressed differently. We do not plan to update these forward-looking statements. You should be aware that our actual results could differ materially from those contained in the forward-looking statements due to a number of risks affecting our business. These risks include, but are not limited to (a) our ability to successfully commercialize and market ANTARA or FACTIVE due to: the limitations on our resources and experience in the commercialization of products; lack of acceptance by physicians, patients and third party payors; unanticipated safety, product liability, efficacy, or other regulatory issues; delays in recruiting and training sales personnel; problems relating to manufacturing or supply; delays in the supply of products by the third party manufacturers and suppliers on which we rely; inadequate distribution of the products by wholesalers, pharmacies, hospitals and other customers; and competition from other products; (b) our ability to integrate ANTARA into our business; (c) whether we will be able to expand the indications for which FACTIVE is approved;(d) the delay in or inability to obtain additional regulatory approvals of our products and product candidates due to negative, inconclusive or insufficient results in ongoing or future clinical trials, the FDA requiring additional information or data, delays in the progress of ongoing clinical trials, safety concerns arising with respect to our products or product candidates and disputes with the third parties from whom we license our products or product candidate; (e) delays by the FDA; (f) the Company's inability to raise additional capital on favorable terms or at all and (g) claims against us by third parties, including claims relating to our intellectual property position. Additional factors that could cause actual results to differ materially from those projected or suggested in any forward-looking statements are described under the heading "Risk Factors" in the Company's Quarterly Report on Form 10-Q for the quarter ending September 30, 2006 and in other filings that we may make with the Securities and Exchange Commission from time to time.