PS-targeting antibodies can block HIV virus from entering into certain blood cells

Peregrine Pharmaceuticals, Inc. (Nasdaq: PPHM) today announced the publication of data showing phosphatidylserine (PS)-targeting antibodies can block one of the key ways the AIDS virus gains entry into certain blood cells.  The data were generated by scientists at Duke University as part of their ongoing AIDS vaccine research.  The article titled "Anti-Phospholipid Human Monoclonal Antibodies Inhibit CCR5-Tropic HIV-1 and Induces Beta-Chemokines" is available online today and will be published in the April 12, 2010 edition of the Journal of Experimental Medicine.  Peregrine's PS-targeting antibodies are currently in clinical development for the treatment of cancer and HCV infections.

In early stage in vitro studies reported by Dr. Anthony Moody of Duke University, lead author of the publication, PS-targeting antibodies developed or licensed by Peregrine blocked HIV from docking with its most commonly used entry point into blood cells--the CCR5 receptor.  The antibodies accomplished this indirectly, by binding to white blood cells called monocytes and causing them to secrete proteins called chemokines, which have the ability to block entry of HIV into the cell.  In the presence of monocytes, the antibodies prevented HIV infection in vitro 85% of the time in these studies.

Investigators believe the finding has particular strategic importance because most HIV strains use the CCR5 receptor to gain entry into a cell.  In addition, it is one of the earliest events in the process of infection, so being able to intervene at this juncture could potentially be clinically useful.

Dr. Philip Thorpe, professor of pharmacology at UT Southwestern Medical Center, a pioneer in the development of PS-targeting therapies and an author of the new publication commented, "This study from our colleagues at Duke University illuminates another intriguing aspect of phospholipid-targeting antibodies--the diversity of their anti-viral mechanisms and broad spectrum anti-viral potential.  The PS-targeting antibodies in this study showed potent ability to induce specific effects that impact viruses, in this case by stimulating the production of immune-related proteins that block the entry of HIV into cells.  We look forward to the results of additional studies of these antibodies that are planned at Duke."

Barton Haynes, M.D., director of the Duke Human Vaccine Institute and senior author of the study commented, "These results indicate that targeting a host cell lipid such as PS as an anti-viral strategy is a promising concept of relevance to new therapeutic and possibly prophylactic innovations for HIV."

Peregrine's most advanced PS-targeting antibody bavituximab is currently being studied in a clinical trial for the treatment of patients co-infected with hepatitis C virus (HCV) and HIV.  Earlier Phase I studies in HCV patients showed that bavituximab was well tolerated and it exhibited encouraging signs of anti-viral activity.  Under a major biodefense initiative, bavituximab and a fully human equivalent antibody are also in preclinical development for the treatment of viral hemorrhagic fevers (VHF).  In November, 2009 Peregrine researchers presented positive data on progress in this program, showing that the PS-targeting antibodies increase survival in a model of lethal VHF infection.

"This publication is the latest in a series of presentations and publications that supports the potential of PS as a target in HIV infection and provides new insights into the unique mechanisms of action of our PS-targeting antibodies," said Steven W. King, president and CEO of Peregrine.  "While past studies have focused on the broad nature of the PS target, these new data reveal that some of these antibodies may also have highly specific effects."

Anti-Phospholipid Human Monoclonal Antibodies Inhibit CCR5-Tropic HIV-1 and Induces Beta-Chemokines, M. Anthony Moody et al., Journal of Experimental Medicine.  Published Online First April 5, 2010.