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gene therapy FAQ
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Gene Therapy FAQs
Q: What is gene therapy?
A. Gene therapy is an exciting experimental
technique that seeks to provide the body with the genetic information
(DNA) it lacks so that it can perform normal functions. Most gene therapy
strategies use a vector, such as modified virus, to attempt to deliver
a good copy of a gene to a cell that contains a defective gene. Scientists
hope that the transferred
gene will then restore the normal functions. For people with hemophilia,
this means that clotting factor genes inserted into the body would enable
normal clotting factor proteins to be produced for the first time.
Q. Has gene therapy cured any diseases so far?
A. Yes, but rarely. Gene therapy is a very young science that
has been used in patients for only about ten years. Thousands of patients
with cancer and infectious diseases, such as AIDS, have been treated but
have not been cured yet. While these are very difficult diseases to cure,
scientists and physicians have shown that they can transfer genes into
patients, an important first step. Some non-human animals have been cured
of diseases using gene therapy, including dogs with hemophilia.
More recently, some children with no immune systems have been treated
with gene therapy, and appear to be "cured." Their immune systems
have been restored.
Q. Why is hemophilia well-suited for gene therapy?
A. Hemophilia is thought to be a model disease for treatment
with gene therapy because it is caused by a single malfunctioning gene
and only a small increase in clotting factor in the bloodstream could
provide a great medical benefit. Making a patient with severe hemophilia
than 1% factor level) have milder forms (greater than 5 % factor level)
should eliminate spontaneous bleeding episodes.
Q. I heard recently that
someone died as a result of gene therapy trials. Are the people involved
in the hemophilia trials at risk?
A. Katherine High, MD,
a physician and researcher involved in hemophilia B gene therapy trials,
notes that the hemophilia trials are not using the type of vector (adenovirus)
used in the clinical trial that led to the fatality in the other case.
Further, Dr. High points out that there has been no toxicity noted so
far in any of the patients in the hemophilia B gene therapy trial with
which she is involved. Finally, Dr. High emphasizes that the patient who
died had a disease characterized by a deficiency of a liver enzyme required
to remove toxic waste arising from protein breakdown. It is a completely
different disease from hemophilia.
Q. If gene therapy works for my son, does that
mean the chance of someday passing his affected gene to a daughter is
A. No, it doesn't. The genetic information that a person has
inherited from his parents would be passed down to his daughter. Gene
therapy to treat future generations or even unborn children with hemophilia
is a hotly debated ethical issue that will be considered once trials,
such as those currently being performed, are successful.
Q. How long would gene therapy last?
A. No one can predict right now. The goal is for it to last
long as possible, hopefully for years to come.
Q. What if these first trials don't work well enough?
A. Other scientific approaches, using improved viral vectors
carry the genes, are being developed in laboratories around the world.
Some of the most promising new techniques will be tested in persons with
hemophilia in the next one to two years.
Q. What is the hope for gene therapy for hemophilia?
A. Scientists hope that one day gene therapy will provide the
body with the genetic information needed to produce clotting factor on
its own. This would present significant improvement in the lives of persons
with hemophilia. In simple terms, one can think of it as a treatment.
But this treatment would last considerably longer than the 24 to 48 hours
current clotting factor replacement therapy lasts. That would make the
gene therapy "treatment" essentially a cure.
Q. What about gene therapy for other bleeding
A. Most attention has been focused on factor VIII and factor
IX deficiency. However, once positive results are seen in persons with
these bleeding disorders, the stage will be set to develop therapies for
rarer clotting factor deficiencies, including von Willebrand disease.
Q. How can I get involved?
A. It will be important for the community to advocate and raise
funds to more rapidly move gene therapy for hemophilia towards reality.
Getting more scientists to do research on hemophilia, both at medical
schools and in the biotechnology industry, will accelerate the cure. Since
no one can predict which method for delivering the genes is best, it helps
for different scientific groups to use many different techniques. The
best ones will eventually get sorted out and pursued.
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