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Gene Therapy

Gene therapy represents a new field of medicine, one which can potentially cure many genetic diseases such as bleeding disorders. Patients with inherited diseases such as hemophilia usually lack a functional protein, which can be replaced with periodic protein replacement therapy. An alternative is to add a normal gene to substitute for the defective one. The normal gene, if delivered to the right cells and in sufficient quantity, can continuously make the normal version of the defective protein, restoring normal clotting mechanisms.

However, this is a new and highly experimental field. Many questions remain unanswered and will only be answered through a series of clinical studies, some of which are ongoing using the genes for factors VIII and IX. There have been many failures and disapointments when investigators have found that the technology for delivering the genes was inadequate when used in humans. Sometimes investigators have underestimated the complexity of the diseases they were attempting to cure. Because of some recent successes, hemophilia has emerged as the top candidate for a genetic disease most likely to benefit from gene therapy.

Hemophilia is considered an ideal disease for gene therapy because it's caused by a single malfunctioning gene, and only a small increase in clotting factor in the bloodstream could provide great medical benefits. If gene therapy raises levels of missing clotting factors by as little as 2% of normal, it is enough to prevent patients from suffering spontaneous hemorrhages into joints, brain and other organs, as happens with hemophilia. Levels greater than 20% to 30% would be sufficient to prevent bleeding in all but the most traumatic injuries.

Although gene therapy could potentially replace treatment for hemophilia, it only corrects the defect in the hemophilic individual, not in their genetic line. Affected individuals would still pass hemophilia to their descendants.

Treatment that would correct the defect in all cells, including reproductive cells, is called germline therapy. It would have to be done at the embryo stage of conception. There are many ethical considerations that will need to be addressed before germline therapy is attempted in humans.

The information contained on the NHF web site is provided for your general information only. NHF does not give medical advice or engage in the practice of medicine. NHF under no circumstances recommends particular treatment for specific individuals and in all cases recommends that you consult your physician or local treatment center before pursuing any course of treatment.
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