Evaluate the Tolerability and Therapeutic Effects of Repeated Doses of Autologous T Cells With VRX496 in HIV

HIV-based antisense vectors may provide several important advantages over current HIV combination therapies. VIRxSYS Corporation (VIRxSYS) is developing the candidate clinical vector VRX496. VRX496 is an HIV-based lentiviral vector containing an anti-HIV antisense sequence targeted to the HIV envelope (env) coding sequence. First, HIV-1 vectors are likely to be less toxic than current combination drug therapies because the genetic antisense antiviral is expressed only in cells that become infected with wt-HIV. The payload is located upstream of a major splice acceptor site and is thus dependent on the expression of Tat and Rev proteins that are provided by wt-HIV. Second, the length of the antisense region is over 900 nucleotides long, making it difficult for wt-HIV to create resistant strains that are sufficiently fit to cause disease. Third, HIV vectors are predicted to be safe because no novel genetic sequences are introduced into the patient (i.e., no novel functional genes are contained in the HIV-1 vector). All the sequences present in the vector are derived from highly conserved regions of wt-HIV that would almost certainly be present in any HIV-1-infected individual. The HIV sequences that are used to create VRX496 are solely derived from pNL4-3, a prototypic HIV-1 molecular clone that is derived from two North American strains of HIV-1.

In the present trial, T cells will be harvested from infected individuals, transduced ex vivo with the vector at the University of Pennsylvania, and then reintroduced by autologous transfusions. VIRxSYS recently completed a Phase 1 clinical study at the University of Pennsylvania of the vector VRX496 in 5 HIV-positive subjects who had failed at least two HAART regimens. Data available to date for the primary endpoints, viral load and CD4 counts, are promising. Specifically, 4 of 5 subjects had stable or increased CD4 counts, and viral loads were stable in 4 of 5 patients, and decreased by 1.7 log in 1 of 5 subjects following a single infusion of VRX496 T cells. In the present trial, subjects will receive up to 6 infusions of VRX496 modified CD4 T cells, and then undergo a series of tests, including rectal mucosal biopsies, to determine the longevity and trafficking of the VRX496 T cells. In addition, subjects will have the opportunity to have a supervised drug holiday (structured treatment interruption) to determine if the VRX496 have an antiviral effect.