Nabi Biopharmaceuticals has signed a definitive agreement for the sale of PentaStaph (Pentavalent S. aureus Vaccine) and related assets to GlaxoSmithKline (GSK) for a total consideration of up to $46 million.

Under the terms of the agreement, Nabi will receive an initial cash payment of $20 million when the transaction closes plus an additional $26 million contingent upon four milestone accomplishments. The sale is subject to satisfaction of certain customary closing conditions by the buyer and seller prior to closing. Nabi anticipates closing the sale before year-end 2009 and completing the milestones within the next 18 months.

Key opinion leaders believe that successful development of a vaccine against S. aureus is critical in the fight against this multidrug-resistant bacterium. MRSA, or Methicillin-resistant S. aureus, is an increasingly prevalent strain of the bacterium. MRSA is especially troublesome in hospital-associated nosocomial infections where patients with open wounds, invasive devices and those undergoing surgery are at a greater risk of infection. MRSA is also occurring in otherwise healthy people who have not been recently hospitalized and usually manifests as skin infections through cuts, pimples and boils.

"We are very pleased that GSK is acquiring the PentaStaph programme and undertaking its further development and commercialization in this area of high unmet medical need. This transaction is the next step in the execution of our strategic alternatives process and we are pleased to be able to generate near-term value from this program for our shareholders," said Dr. Raafat Fahim, president and chief executive officer of Nabi Biopharmaceuticals. "We believe in the potential of PentaStaph and are confident that GSK will continue to develop this vaccine into a successful weapon against the growing threat from Staphylococcus infection."

PentaStaph (Pentavalent S. aureus Vaccine) is Nabi's five-component vaccine candidate against S. aureus infections. Three of the antigen components induce the production of antibodies that target S. aureus polysaccharides (Types 5 & 8 capsular polysaccharides and Type 336 cell-wall polysaccharide) which enhance the immune systems' ability to clear the bacteria. Types 5 & 8 capsular polysaccharides are expressed in approximately 80 percent of S. aureus strains, including many of the known MRSA (methicillin-resistant S. aureus) strains. Type 336 polysaccharide accounts for approximately 20 per cent of S. aureus infections that do not form a polysaccharide capsule in the human bloodstream. Two additional antigen components induce the production of antibodies that target two of the most virulent toxins produced by the bacteria which can significantly debilitate the human immune system: Panton-Valentine Leukocidin found predominantly in community-acquired MRSA, and alpha toxin, produced by almost all S. aureus isolates. This multi-target approach which enhances the immune system's ability to eliminate a broad spectrum of S. aureus strains and neutralizes the bacterial defenses of the most virulent strains has been demonstrated in pre-clinical animal models to provide significant efficacy against the bacteria which is hoped would translate into human efficacy.

Nabi Biopharmaceuticals leverages its experience and knowledge in powering the immune system to develop products that target serious medical conditions in the areas of nicotine addiction and gram-positive bacterial infections.