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Pushing the Limits of the Human Body

Genetic Perfection Main

Introductory Notes

The Biology of Gene Therapy

Future direction of Gene Therapy

Glossary

References

On This Page:

Current Research and Successes

Current Failures and Safety Issues

Ethics

In September 2004, the first patient to undergo gene therapy for Parkinson’s disease completed Phase I of a clinical trial. This patient had a gene introduced into his body via a virus that brought the desired gene to the brain where it has helped reduce the symptoms of Parkinson’s disease including tremors and uncontrolled movements. “Introducing this gene leads to the production of natural chemicals that inhibit the overactive brain cells” (Newswise, 9/2/04).

Researchers have used a new technique that can successfully deliver a gene of interest into the eyes of cats suffering from glaucoma. In this technique, a viral vector was injected into the eye of the cat through the cornea. The viral vector reached its target within the eye of the cat and has remained in its proper location for over a year. The gene used in this study was not one that will cure glaucoma but rather a gene that glowed green under UV light when active. This gene was chosen primarily to determine if the delivery system the researchers chose worked correctly. All of the cats treated with this technique had eyes that glowed green under UV light, proving that the gene was active within the eye (Newswise, 9/1/04).

In August 2004, two little boys from Indiana were accepted into a clinical trial for Batten Disease. Batten Disease is a disease of the central nervous system that is extremely rare. The devastating symptoms of the disease include blindness, paralysis, and complete loss of communication skills. This disease is currently always fatal and not preventable (BDSRA, 2004).

This clinical trial involved the drilling of small holes into the brains of the two boys and introducing a viral vector that contained copies of functional genes that could potentially save their lives. While the trial is still in the early stages, the implications that this may work have provided hope to families who have loved ones that suffer from this disease (Kelly, 2004).

This disease is also known as Bubble Boy Disease. It has received its name due to the fact that those who suffer from it must remain in complete isolation without any contact with the outside world. Those who suffer from this disease lack a gene that allows for the maturation of the immune system. Thus, SCID sufferers do not have an active immune system to fight off even the simplest of diseases. A common cold has the ability to kill a person with this disease.

Please see the figure below for a schematic diagram of the treatment of a patient with SCID.

Figure 4: Schematic of the treatment of a patient with SCID. Image taken from http://www.fda.gov/fdac.features/2000/gene.html.

The above figure represents the current method of treating those with SCID. Viral vectors that contain the gene that is missing from those with SCID are injected into bone marrow cells. The bone marrow cells are then transferred to the patient via an IV. The patient’s immune system is restored, and the patient can live a normal life outside of isolation. Several studies have shown that this technique has worked and many children suffering from this disease have been cured and are able to live completely normal lives (FDA, 2000). “French scientists reported convincing evidence that they successfully treated a different form of SCID…with gene therapy. Four of the first five babies treated…have had ‘a complete or near complete recovery’ of their immune systems after the treatment” (Thompson, 2000).

In 1999, a teenager died from gene therapy attempting to cure a disease called OTCD (ornithine transcarboxylase deficiency). During the trial, Jesse Gelsinger was injected with an adenovirus carrying the corrected gene for OTCD. Four days after receiving the therapy, he died. No one is really sure why he died, but researchers suspect that it was an immune response to the adenovirus. His body recognized the adenovirus as a foreign agent and attacked it, causing a huge increase in his white blood cell counts and leading to his death (Thompson, 2000).

In January 2003, the FDA halted all gene therapy trials using retroviruses because there were problems observed in French research. Specifically, several children developed a leukemia-like condition after being treated with gene therapy for SCID (Gene Therapy).

Gene therapy is very short lived and may require many treatments with potentially dangerous viruses before a “cure” is obtained. Also, there are problems with viral loads in the body. There is no evidence to support that the virus carriers are completely safe. What will keep the viruses from becoming potentially dangerous pathogens once inside the body? Another problem with gene therapy is that we cannot cure diseases that have multiple causes, whether genetic or environmental. Some diseases such as cancer and Alzheimer’s Disease are the result of many genes and environmental factors (Gene Therapy).

“The Food and Drug Administration (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” (Gene Therapy). It can be seen from the quote above that gene therapy is still being perfected and it may be many years before any conclusive results and “cures” are available from the current clinical trials.

Gene therapy raises some major ethical issues. Since we are treating various disorders with gene therapy, we are labeling them as bad or unwanted in society. Do we view people with these disorders as equals or those who have something wrong with them that needs to be fixed? Also, who deserves gene therapy? Is it something that insurance will potentially cover or will it only be available to those who can pay? For a more complete analysis of the ethical implications of gene therapy, please visit the Ethics section of the Genetics page.

This web page was produced as an assignment for an undergraduate course at Davidson College.