Hollywood loves stories were science experiments on human beings turn into apocalyptic disasters. Last year, Rise of the Planet of the Apes depicted a new gene therapy for Alzheimer’s disease. The chimpanzees in the experiment develop human-like intelligence and revolt. In the movie I am Legend, a virus created to cure cancer accidentally wipes out 90% of the world’s population. The truth about gene therapy is better than the movies, and it is quietly making progress to treat a range of diseases.
Gene therapy uses a variety of ways to insert a gene into the DNA of a patient’s diseased cells. The inserted gene can replace the defective gene, turn off a bad gene, or add a new gene to help fight the disease. Researchers are investigating treatments for inherited genetic disorders, some cancers, and viral infections such as HIV.
Clinical trials for gene therapy had a rough start. In 1999, 18-year-old Jesse Gelsinger became the first person to receive gene therapy for an inherited liver disorder. Quite tragically, he died shortly after receiving the therapy. His body rejected the virus that was used to deliver the corrected gene. The FDA investigated and concluded that the researchers were at fault. They did not fully disclose to Jesse the risk of serious side effects, and that animals had died from the same therapy.
Deciding which patients are eligible is one of the most important considerations in a clinical trial. Because of the potential serious risks, only patients with severe and life threatening disorders may be candidates for gene therapy. Jesse should never have been permitted to take part in the clinical trial since his disease could have been managed with a special diet and medications.
So far, only a small number of patients have been treated successfully. Some have Severe Combined Immunodeficiency, the “bubble boy” disease. Others have been treated for the brain disease Adrenoleukodystrophy[1], featured in the movie Lorenzo’s Oil. More recently gene therapy has restored sight to patients with congenital blindness,[2] to cure hemophilia[3], and to help patients with Parkinson’s.[4]
One risk of gene therapy is that while it treats one disease, the altered DNA could trigger cancer and cause tumors. The “cure” may also be temporary, requiring the patient to undergo additional rounds of treatment, with increased risk of side effects.
There are many ethical issues, but I’ll point out just two from the patient’s perspective. One is the principle “do no harm.” This means that the potential benefit must outweigh the possible risks. Another ethical issue is ensuring informed consent, that is, making sure that patients fully understand the procedure, its risks and its limitations. This is based on respect for them as persons who have dignity.
The truth is, gene therapy may not cause a Hollywood catastrophe, but because we’re dealing with real human beings with real diseases, we should proceed, but let’s tread carefully. That could produce a movie with a happy ending.
[1] “Gene Therapy Technique Slows Brain Disease ALD Featured In Movie 'Lorenzo's Oil',” ScienceNews, November 5, 2009, http://www.sciencedaily.com/releases/2009/11/091105143706.htm (accessed April 5, 2012).
[2] Gene Therapy Proves Effective In Treating Blindness Medical News Today, February 9, 2012, http://www.medicalnewstoday.com/articles/241376.php (accessed April 5, 2012).
[3] “Hemophilia B - Single Gene Therapy Treatment Offers Significant Improvement,” Medical News Today, December 11, 2011, http://www.medicalnewstoday.com/articles/238992.php (accessed April 5, 2012).
[4] “Gene Therapy Trial For Parkinson's Disease Effective In Improving Motor Function,” Medical News Today, March 19, 2011, http://www.medicalnewstoday.com/articles/219638.php (accessed April 5, 2012).