The treatment capitalizes on improvements made over recent years in the use of vectors derived from lentiviruses, a retroviral subfamily that includes HIV. Only lentiviral and oncoretroviral vectors can permanently integrate into the genomes of blood stem cells, which are mostly nondividing in their primitive state and are central to treating diseases of the blood and immune system. But when oncoretroviral vectors are used, the transgene fails to express sufficiently, for unknown reasons. That leaves the field to lentiviral vectors, and the leading such vehicle is based on HIV-1.
Inder Verma, whose lab at the Salk Institute for Biological Sciences first developed an HIV-based lentiviral vector for transduction of nondividing cells,1 was at the October FDA meeting and says the questions asked of VIRxSYS seemed "completely answerable." He thinks the trial will go forward and believes it's "not a bad idea." Noting that vectors based on equine and feline lentiviruses ...
