The Promise of Gene Therapy

Since scientists and researchers continue to evaluate gene therapy in laboratory and clinical research studies, the potential advantages are still largely unknown.

Potential advantages: May optimize cancer treatments

Gene therapy poses a number of risks. The way the genes are delivered and the different vectors may present the following risks.

• DNA mutations The new gene might be inserted in the wrong location in the DNA, which might cause harmful mutations to the DNA or even cancer.
• Immune response The body's immune system may see the newly introduced viruses as intruders and attack them resulting in inflammation, toxicity, as well as organ failure in severe cases.
• Viral spread Because viruses can affect more than one type of cell, it is possible that the viral vectors may infect cells beyond just those containing mutated or missing genes. If this happens, healthy cells may be damaged and cause other illness or diseases, including cancer.
• Reversion of the virus to its original formOnce introduced into the body, the viruses may recover their original ability to cause disease.
• Risk to offspring The new DNA may affect reproductive cells - egg cells in women and sperm cells in men. This could result in genetic changes affecting children born after treatment.
• High cost
• Potential for short-term efficacy

What is the availability of gene therapy?

Gene therapy is available only through clinical trials (research studies in people). Health insurance companies may or may not provide coverage for gene therapy, which may be very expensive. Ask your oncologist about gene therapy for your diagnosis, and the potential for combining them with other cancer therapies.

What is the future of gene therapy?

The FDA has not yet approved any human gene therapy product for sale. Current gene therapy is experimental and has not proven very successful in clinical trials.

Little progress has been made since the first gene therapy clinical trial began in 1990. In 1999, gene therapy suffered a major setback with the death of 18-year-old Jesse Gelsinger.

Another major blow came in January 2003, when the FDA placed a temporary halt on all gene therapy trials using retroviral vectors in blood stem cells. FDA took this action after it learned that a second child treated in a French gene therapy trial had developed a leukemia-like condition. Both this child and another who had developed a similar condition in August 2002 had been successfully treated by gene therapy for X-linked severe combined immunodeficiency disease (X-SCID), also known as "bubble baby syndrome."

The FDA's Biological Response Modifiers Advisory Committee (BRMAC) met at the end of February 2003 to discuss possible measures that could allow a number of retroviral gene therapy trials for treatment of life-threatening diseases to proceed with appropriate safeguards. In April of 2003 the FDA eased the ban on gene therapy trials using retroviral vectors in blood stem cells.

Gene therapy research continues to focus on the potential safety and efficacy of this treatment. Specific areas of gene therapy research include the following.

• Developing reliable vectors
• Ensuring safety
• Targeting the correct cells
• Preventing genetic changes from being passed on from parents to children

For More Information

• Gene Therapy Net
• International Society for Cell & Gene Therapy for Cancer
• Macmillan Cancer Support Gene Therapy
• National Human Genome Research Institute