Viral Vector Technology for Gene Therapy

Getting to the Root Cause of Disease
Gene therapy is the treatment of hereditary or infectious diseases by repairing or re-engineering the genome. The therapy’s goal is to treat the genetic cause of disease rather than merely treating the symptoms. The advantage of gene therapy over traditional treatments is the elimination or reduction of the toxic side effects that are commonly seen with drugs. Examples of diseases caused by genetic flaws include cancer (genetic flaws in genes that control cell growth), Parkinson’s disease (genetic flaw in a critical neuronal gene) and infectious disease (foreign genetic material invades human cells; i.e. HIV, and HCV).

Solving the Delivery Challenge
The field of gene therapy holds great promise, however, most of these promises have been unfulfilled due to challenges in developing a transport system capable of delivering genetic and therapeutic payloads into targeted cells efficiently, reproducibly, and permanently.

Vectors are vehicles that deliver genetic material into cells. Viral vectors use the backbone of viruses for this purpose. Viruses are very effective at getting into cells, so the first challenge is to remove the disease-causing elements from the virus and leave behind a natural delivery vehicle. VIRxSYS’s HIV-based lentiviral vector platform has achieved this goal and has also overcome other existing challenges, such as high-efficiency gene transfer, stable transfer of genetic material into dividing and non-dividing cells, and a reduced risk of immunogenicity and insertional oncogenesis (cancer). VIRxSYS created VRX496 for the first application of our vector against the target disease, HIV/AIDS. To see how VIRxSYS is using gene therapy to treat HIV click here to view an animation.

VRX496 is created by removing the disease components of HIV and inserting an anti-HIV therapeutic payload, called antisense. The Company has demonstrated that such a vector can inhibit HIV replication by more than 99% (Humeau 2004).

HIV infects human cells very efficiently and, consequently, a vector derived from HIV has these remarkable properties for efficient gene delivery. VIRxSYS has demonstrated that its HIV lentiviral vector can deliver therapeutic payloads into human cells with greater than 90% efficiency, which is remarkable compared with other gene therapy vectors that have reported an efficiency of 20-50%. VIRxSYS’ vector efficiency can be achieved in several important human hematopoietic cell types such as lymphocytes, hematopoietic CD34+ cells, monocyte-derived dendritic cells, and a panel of tumor cell lines.

VIRxSYS is the only company currently testing a lentiviral vector permitted for use by the FDA in Phase II clinical trials. To date, patients in the Company’s clinical trials have experienced no adverse events due to treatment, thus supporting the safety of the Company’s vector for applications in humans.

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