Treatment for HIV patients urgently requires a shot in the arm as current drug therapies have become increasingly less effective and ineffectual for a growing number of sufferers. In addition, the increase in cases of drug resistant HIV-strains means the number of alternatives is steadily decreasing.
Currently there is a range of marketed antiretrovirals for the treatment of HIV, the majority of which were launched between the years 1990 to 2000. Although products with lower pill burden, higher potency and fewer incidences of adverse side effects are gradually replacing these treatments, HIV infection rates are soaring.
VIRxSYS' therapy modifies a patient's own CD4 T cells with the viral vector plus antisense, VRX496, to provide the patient with a number of protected CD4 T cells capable of resisting HIV and protect normal immune system function. The goal of this therapy is to repopulate a patient's immune system with genetically engineered cells that can support immunity both against HIV and other infections.
"VIRxSYS' lentiviral vector is the most efficient clinical genetic vector available today," said Riku Rautsola, CEO of VIRxSYS. "The efficiency of gene transfer combined with a genetic payload instead of a protein payload allows us to overcome major obstacles that have hindered past clinical gene therapy trials."
All five patients in the Phase I study have completed the six-month assessment period. Three of the patients have also reached their one-year post-dosing assessment. All patients have failed 2 highly active antiretroviral drug therapy regimens (HAART regimens) when they were enrolled in the study.
The Phase I clinical trial used an HIV-derived lentiviral vector from which the disease-causing aspects of the virus have been removed, leaving behind an efficient genetic delivery vehicle. This vector is then equipped with an anti-HIV genetic medicine consisting of a long antisense molecule targeted against the HIV envelope gene.
The antisense genetic medicine blocks HIV replication in CD4 T cells, which would otherwise be destroyed by the HIV virus. Without CD4 T cells, the human immune system collapses, allowing the onset of full-blown AIDS.
The progression of the virus inside an infected cell can be prolific. HIV produces new copies of itself, which can then go on to infect other healthy cells within the body. The more cells HIV infects, the greater its impact on the immune system (immunodeficiency). Antiretroviral drugs slow down the replication and, therefore, the spread of the virus within the body, by interfering with its replication process in different ways.
Nucleoside Reverse Transcriptase Inhibitors (NRTIs) reduce an enzyme called reverse transcriptase by preventing the process that replicates the virus's genetic material. HIV needs reverse transcriptase to generate new copies of itself.
Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) also interfere with the replication of HIV by binding to the reverse transcriptase enzyme itself. This prevents the enzyme from working and stops the production of new virus particles in the infected cells.
Protease Inhibitors (PIs) inhibit the digestive enzyme protease that is needed in the replication of HIV to generate new virus particles. It breaks down proteins and enzymes in the infected cells, which can then go on to infect other cells. The protease inhibitors prevent this breakdown of proteins and therefore slow down the production of new virus particles.
Other drugs that inhibit other stages in the virus's cycle (such as entry of the virus and fusion with an uninfected cell) are currently being tested in clinical trials.
A recent market report by Datamonitor's suggests that by 2012, global product sales could amount to just under $12 billion (€9.2 billion), approximately double the value recorded for 2003 ($5.76 billion).