IMMUNOGENICITY STUDY MEETS PRIMARY GOALS OF SAFETY AND IMMUNE RESPONSE

Nabi Biopharmaceuticals announced results from the first in a series of immunogenicity studies of StaphVAX (Staphylococcus aureus Polysaccharide Conjugate Vaccine) in additional patient populations at risk for S. aureus infections. StaphVAX is Nabi Biopharmaceuticals' Phase III investigational vaccine. It is designed to prevent certain prevalent strains of S. aureus bacterial infections.

The risk of developing S. aureus infections is greatest during the immediate postoperative period, while patients are still in the hospital while recovering from surgery. This study was designed to provide evidence that a broader and generally healthier at-risk patient group, such as patients undergoing cardiovascular surgery, can achieve antibody levels equal to, or greater than, the protective antibody levels attained in immunocompromised end-stage renal disease (ESRD) patients in earlier clinical trials.

The Phase II study included a total of 120 patients from 15 cardiovascular surgery centers in the U.S. This two-part, six-month study was double-blinded through the first six weeks following vaccination. Subjects were vaccinated prior to their cardiovascular procedure in order to assess their antibody levels during the period of greatest risk of infection. While these patients were healthier than the ESRD patients studied in the company's Phase III efficacy trial, 25 percent were partially immunocompromised due to diabetes. The vaccine was generally well-tolerated, and no serious adverse events were attributed to it. The second, unblinded phase of the study, which will provide more comprehensive assessment of the duration of vaccine effect in this population by following patients for up to six months, is still ongoing. StaphVAX is currently in a confirmatory Phase III trial designed to confirm that it can prevent such infections in ESRD patients.

It is estimated that there are a total of 12 million patients in the U.S. who are at risk of contracting these infections on an annual basis. S. aureus I, the most common cause of serious hospital-acquired bloodstream infections, can be difficult to treat because the bacteria, in most cases, is resistant to available antibiotics. According to the current estimates by the U.S. Centers for Disease Control and Prevention (CDC), more than two million patients in the U.S. each year contract an infection as a result of exposure to a pathogen while receiving care in a hospital. S. aureus can spread from the blood (bacteremia), to the bones (osteomyelitis), or the inner lining of the heart and its valves (endocarditis), or cause abscesses in internal organs such as the lungs, liver and kidneys.