Friday, May 8, 2009

What are the Risks associated with Gene Therapy

The first death associated with gene therapy occurred on September 18, 1999, at the University of Pennsylvania. Jesse Gelsinger was participating in a clinical trial, a biomedical experiment for evaluation of safety and efficiency of a therapy for a disease. Gelsinger, who was 18 years old at the time of the treatment, had a deficiency of ornithine transcarboamylase, an important enzyme in the metabolism of ammonia. Patients with this rare metabolic disorder must maintain a low-protein diet and take a series of medicines to avoid ammonia poisoning in the blood stream. The gene therapy Gelsinger took triggered a chain reaction in his immune system, resulting in hepatic and respiratory failure, and consequently, his death four days after being treated.

Since Gelsinger's death, the University of Pennsylvania has been reevaluating all procedures involved in the vector engineering and in the administration of the therapy. No flaw has been found that would explain such an extreme reaction by his immune defense system. Ever since, the public and the FDA, the agency responsible for oversight of clinical trials in the United States, have been more skeptical and doubtful about whether current scientific knowledge is enough to justify further investigations with humans. The credibility of gene therapy was seriously damaged, resulting in a temporary moratorium on human clinical trials.

Another challenge to gene therapy has been its ephemeral benefits to patients. This has been observed in several clinical trials with cystic fibrosis and ADA deficiency patients, whose cure faded after a few months of therapy, and was followed by a return of the disease symptoms. A possible explanation for that is that the genetically modified somatic cells decreased in amount. Because they are already differentiated and possess only a limited capability to multiply, it is expected that after they are gone, the treated organ could become diseased again.

Future of Gene Therapy

Although the idea of gene therapy has been around for only 20 years, the technique has been drawing a great deal of interest and curiosity through the world. The first trials generated great expectations within the scientific community. Although there have been several disappointments, many believe that it is just a matter of time before the technical and scientific details are mastered and the procedures become routine. This research is being advanced worldwide. In fact, Alain Fischer, a medical doctor in Paris, France, reported the complete cure of two children who had a rare immune deficiency condition.

Another promising result from stem cell research has been reported in type-B hemophilia patients at the Children's Hospital in Philadelphia and at Stanford University, where patients treated with gene therapy presented a reduction in the period for blood coagulation. ADA deficiency, a disease caused by a defective gene for the ADA enzyme present on human chromosome 20 has been a focus for gene therapy in many institutions. In one of the cases, several patients treated with the corrective gene were able to reconstitute their immune systems and are living normal lives out of the isolated bubbles that are needed to maintain an environment free from microbes. The patients started to produce a correct ADA enzyme after receiving the gene therapy.

The potential use of this therapy to cure other more complicated diseases, such as cancer and coronary diseases, also seems promising. Gene therapy is still in its infancy, but it is believed that as it matures, it will become an effective treatment for the myriad of genetic diseases that affect humanity.

Tags: Bio Technology, Bio Genetics, Gene Therapy

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