Clinical Data on FACTIVE(R) Tablets for ABS and AECB Presented at the 43rd Annual Meeting of the Infectious Diseases Society of America.

SAN FRANCISCO -- Program includes meta-analysis of clinical trial data in acute bacterial sinusitis and acute bacterial exacerbations of chronic bronchitis in at-risk populations

The 43rd Annual Meeting of the Infectious Diseases Society of America (IDSA) features clinical data on Oscient Pharmaceuticals' (Nasdaq: OSCI) FDA-approved fluoroquinolone antibiotic, FACTIVE(R) (gemifloxacin mesylate) tablets.

In a poster session titled "Dual Action of Gemifloxacin in Acute Bacterial Sinusitis in Patients with Allergic Rhinitis: Antibacterial and Immunomodulatory Effects," researchers will present data obtained from the Phase III program studying FACTIVE for the potential treatment of acute bacterial sinusitis (ABS). The data are based on a meta-analysis of four pooled Phase III studies and examined the efficacy of FACTIVE in treating ABS in a specific sub-population of patients, those with allergic rhinitis. The retrospective analysis determined that FACTIVE, compared to the other drugs studied (cefuroxime and trovafloxacin), was more effective in treating ABS in patients with allergic rhinitis: clinical success rates at end of therapy, gemifloxacin 89.3%, comparators 77.0% (p=0.01); clinical success rates at follow-up, gemifloxacin 79.9%, comparators 66.3% (p=0.019).

"Treating patients with acute bacterial sinusitis due to allergic rhinitis can be challenging because these patients have high levels of inflammation," stated Jack Anon, MD, lead investigator and Clinical Professor, The University of Pittsburgh School of Medicine, Department of Otolaryngology. "Gemifloxacin's clinical utility, particularly in this sub-population, demonstrates the drug's promise in treating ABS."

In a second presentation titled "The Effect of Underlying Chronic Obstructive Pulmonary Disease on Clinical Outcome of Acute Exacerbations of Chronic Bronchitis Treated with Gemifloxacin," researchers examined the differences in clinical outcome among patients with various underlying medical conditions, such as asthma and sinusitis, suffering from acute bacterial exacerbations of chronic bronchitis (AECB). The analysis was based on pooled data from ten Phase III AECB trials. End of therapy clinical response rates were similar, about 90%, for all treatment arms including gemifloxacin, clarithromycin, levofloxacin, trovafloxacin, amoxicillin-clavulanate, ceftriaxone/cefuroxime and ofloxacin.

"As the body of scientific evidence supporting the efficacy of FACTIVE grows, we remain committed to pursuing expanded indications for the drug," stated Steven M. Rauscher, President and Chief Executive Officer. "It is our plan to file a supplemental New Drug Application for FACTIVE this year seeking approval for the five-day treatment of community-acquired pneumonia of mild to moderate severity and for the five-day treatment of acute bacterial sinusitis."

The 43rd Annual Meeting of IDSA, held in San Francisco October 6-9, brings together physicians, scientists and healthcare workers for peer-reviewed presentations of new research in infectious diseases.

FACTIVE is not approved by the FDA for the treatment of acute bacterial sinusitis.

About Oscient Pharmaceuticals

Oscient Pharmaceuticals Corporation is a biopharmaceutical company committed to the clinical development and commercialization of novel therapeutics to address unmet medical needs. The Company is marketing FACTIVE(R) (gemifloxacin mesylate) tablets, approved by the FDA for the treatment of acute bacterial exacerbations of chronic bronchitis and mild to moderate community-acquired pneumonia. In addition to the oral tablet form, Oscient is developing an investigational FACTIVE intravenous formulation for use in hospitalized patients. The Company is also promoting Auxilium Pharmaceuticals' TESTIM(R) 1% testosterone gel to primary care physicians in the U.S. Oscient has a novel antibiotic candidate, Ramoplanin, in advanced clinical development for the treatment of Clostridium difficile-associated diarrhea (CDAD).

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 press release may contain forward-looking statements, as defined by the Private Securities Litigation Reform Act of 1995, including statements regarding (i) possible expansion of the indications for which FACTIVE is approved and (ii) the timing of the filing of a New Drug Application for the use of FACTIVE to treat acute bacterial sinusitis and community-acquired pneumonia with a five day course of therapy. These statements represent, among other things, the expectations, beliefs, plans and objectives of management and/or assumptions underlying or judgments concerning matters discussed in this document. 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, (i) whether we will be able to file the proposed NDA prior to the end of the year and whether any such NDA will be approved so that we can expand the indications for which FACTIVE is approved, (ii) 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 candidates and (iii) our inability to successfully commercialize FACTIVE or promote TESTIM 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; inadequate distribution of the products by wholesalers, pharmacies, hospitals and other customers; and competition from other products. Additional factors that could cause actual results to differ materially from those projected or suggested in any forward-looking statement are described under the heading "Factors Affecting Future Operating Results" in "Management's Discussion and Analysis of Financial Condition and Results of Operations" in the Company's Quarterly Report on Form 10-Q for the quarter ending June 30, 2005 and in other filings that we may make with the Securities and Exchange Commission from time to time.