Peninsula Pharmaceuticals, Inc. Announces Results of Preclinical Study Comparing Nebulized Doripenem vs. Tobramycin in a Murine Model of Acute, Severe Pseudomonas aeruginosa Pneumonia

Peninsula Pharmaceuticals, Inc., a privately-held biopharmaceutical company, today announced the results of a preclinical study comparing nebulized doripenem vs. tobramycin (currently marketed as TOBI) in a murine model of acute, severe Pseudomonas aeruginosa pneumonia. The study, conducted by Lawson Health Research Institute, London Health Sciences Centre, University of Western Ontario and Peninsula Pharmaceuticals, reported that doripenem demonstrated a greater efficacy in reducing bacterial load compared to tobramycin, the only currently approved inhaled antibiotic therapy for the management of pulmonary infections in patients with cystic fibrosis. Based on these and other preclinical results, Peninsula believes that doripenem is a candidate for clinical development as an inhaled antibiotic to manage pulmonary infections caused by P. aeruginosa or other susceptible pathogens in humans. Detailed results of this preclinical study will be presented at the 100th International Conference of the American Thoracic Society to be held in Orlando, Florida from May 21 to May 26, 2004.

Three dose regimens of nebulized doripenem and tobramycin were evaluated and researchers assessed the effects of each on mortality, pulmonary bacterial load and pulmonary neutrophil infiltration in mice with acute, severe P. aeruginosa pneumonia. While both nebulized compounds significantly reduced pulmonary bacterial load at 10 and 20mg/kg, doripenem had a clear dose-dependent response and had greater effect at the highest dose, resulting in a 5 log reduction in pulmonary bacterial load (p<0.05 vs. tobramycin). The reduction in bacterial load was associated with decreased pulmonary inflammation and a lower incidence of mortality.

Peninsula currently has an ongoing Phase I clinical trial in the United Kingdom to assess the safety and tolerability of doripenem for inhalation in healthy volunteers. The first phase of the trial, an ascending multiple dose study, was completed in February 2004, and the second phase, a 14 day multiple dose study, is ongoing.

"The administration of nebulized tobramycin has been a useful therapy to reduce exacerbations of P. aeruginosa in cystic fibrosis patients," said Matthew A. Wikler, M.D., FIDSA, Chief Medical Officer and Executive Vice President at Peninsula. "We are excited by the results of our preclinical comparison of nebulized doripenem and tobramycin and plan to initiate studies in patients with cystic fibrosis in the hopes of demonstrating clinical advantages."

Doripenem is the latest broad spectrum carbapenem antibiotic belonging to the beta-lactam class of antibiotics. According to IMS Health Incorporated, beta-lactam antibiotics were the most commonly prescribed antibiotics in the world based on 2002 sales. According to sales figures reported by pharmaceutical companies, carbapenem antibiotic worldwide sales increased 13.8% to over $1 billion in 2003 compared to 2002. Peninsula licensed North American, South American, and European rights for doripenem from Shionogi & Co. Ltd.

About Peninsula
Peninsula Pharmaceuticals Inc., located in Alameda, California is focused on developing and commercializing antibiotics to treat life threatening infections. For additional company information, please visit Peninsula on the World Wide Web at www.peninsulapharm.com.

About Shionogi
Shionogi & Co., Ltd. is one of Japan's largest research based pharmaceutical companies: developing, manufacturing, distributing, importing and exporting pharmaceuticals and diagnostics. Shionogi's fundamental company policy is to constantly strive to provide medicine of the best possible kind essential for the protection of the health of people world-wide. For additional company information, please visit Shionogi & Co., Ltd. on the World Wide Web at www.shionogi.co.jp.