Genetically Engineered Poison That Targets HIV is Studied in Humans

National Institute of Allergy and Infectious Diseases
4Update
EMBARGOED FOR RELEASE NATIONAL INSTITUTES OF HEALTH
Monday, July 20, 1992 Marion E. Glick
9:45 a.m. (3:45 a.m. EDT) [phone]
Genetically Engineered Poison That Targets HIV is Studied in Humans
In the first study of this type in humans, investigators at the National Institute of Allergy and
Infectious Diseases (NIAID) have safely given single, low doses of a genetically engineered drug that
selectively destroys cells infected with the AIDS virus, HIV. The drug combines portions of a potent
bacterial poison with a protein that carefully directs the poison to HJV-infected cells.
"Further studies will be needed to see if this hybrid drug is as effective in killing HIV-infected
cells in individuals as it has been in laboratory studies," says Richard T. Davey, Jr., M.D., principal
investigator of the study. Dr. Davey plans to present the study findings at an oral session July 20 at
the VIII International Conference on AIDS in Amsterdam.
The drug, soluble CD4-Pseudomonas Exotoxin (sCD4-PE40), uses a toxin produced by the
bacteria Pseudomonas in which the normal targeting portion, known as a binding molecule, has been
replaced by a shortened form of the human CD4 protein. CD4 normally is produced by human CD4+
white blood cells. A specific surface protein, gpl20, found on HlV-infected cells will recognize and
bind to this substituted binding molecule. The gpl20 protein binds to the CD4 molecule whether it
is on the exterior of a cell or incorporated into a drug, such as sCD4-PE40.
When a HIV-infected cell binds to sCD4-PE4O, the toxin molecule rapidly is taken inside the
cell and proceeds to poison the cell's metabolic machinery, quickly killing the cell. Cells that do not
have the viral gpl20 protein on their surface should not bind with sCD4-PE4O and should remain
unharmed by this drug.

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