Over the past several decades, many bacteria have developed resistance to currently marketed antibiotics. If bacteria are resistant, the infection can become difficult or impossible to treat, and may lead to death. Today, many of the major bacterial species that cause serious infections are developing resistance to existing antibiotic therapies. For example, according to studies conducted on bacterial resistance, the infecting bacteria were resistant to methicillin in 45% of all Staphylococcus aureus infections. The U.S. Centers for Disease Control has stated that antibiotic resistance is among that organization’s top concerns.

Antibiotics are effective against some but not all bacteria. Many serious infections that occur in hospitalized patients are complicated and may be caused by more than one kind of bacteria. Because these patients are seriously ill and require immediate treatment, physicians typically cannot wait for the results of a test to determine the exact species of bacteria causing the infection. As a result, physicians typically prescribe a combination of antibiotics effective against the broadest spectrum of bacteria.

Many current antibiotics have been associated with serious side effects, including renal toxicities, heart rhythm abnormalities, photosensitivity, rash and central nervous system toxicities such as seizures. These side effects limit the use of antibiotics in certain patients. Further, these safety problems can be exacerbated by the increased doses often needed to treat resistant bacteria.

Doripenem is a new member of the carbapenem class of beta-lactam antibiotics. Carbapenems have been used for almost 20 years for the treatment of serious, hospital-acquired infections. Carbapenems have generally shown potent, broad-spectrum bactericidal activity, particularly against resistant bacteria commonly found in the hospital. According to sales figures reported by pharmaceutical companies, carbapenems generated over $880 million in worldwide sales in 2002.

The Company is currently developing doripenem for injection for the treatment of serious bacterial infections in the hospital. The Company has passes through phases I and II and plans to initiate phase III clinical program for doripenem for injection in the first half of 2004. The Company’s phase III program will include six separate trials to study doripenem for injection in three distinct indications: complicated urinary tract infections, including pyelonephritis, complicated intra-abdominal infections and hospital-acquired pneumonias. If approved for these three indications, doripenem for injection could be used to treat a broad range of infections that require intravenous administration of antibiotics.

The Company is also developing doripenem for inhalation for the management of pulmonary infections due to P. aeruginosa and B. cepacia in CF patients. Inhalation of doripenem enables the delivery of this compound at high concentrations directly into the lungs to manage these serious pulmonary infections.

PPI-0903 is a next-generation cephalosporin, a member of the beta-lactam class of antibiotics. Cephalosporins are commonly used as a first line therapy for the treatment of hospital-based infections due to their favorable safety profiles and efficacy. Cephalosporins are the most frequently-utilized antibiotics, generating $7 billion in worldwide sales in 2002.

In the Company’spreclinical studies, PPI-0903 has demonstrated broad antibacterial potency against Gram-positive and Gram-negative bacteria, including drug resistant Gram-positive bacteria.