treatment for Cystic Fibrosis. A cure for AIDS. The end of
cancer. That's what the newspapers promised us in the early
1990's. Gene therapy was the answer to what ailed us. Scientists
had at last learned how to insert healthy genes into unhealthy
people. And those healthy genes would either replace the bad
genes causing diseases like CF, sickle-cell anemia and hemophilia
or stimulate the body's own immune system to rid itself of
HIV and some forms of cancer. A decade later, none of these
treatments have come to fruition and research into gene therapy
has become politically unpopular, making clinical trials hard
to approve and research dollars hard to come by. But some
researchers who are taking a different approach to gene therapy
could be on the road to more success than ever before.
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as soon as Watson and Crick unwound the double helix in the
1950's, researchers began considering the possibility- and
ethics- of gene therapy. The goals were lofty- to fix inherited
genetic diseases such as Cystic Fibrosis and hemophilia forever.
therapists planned to isolate the relevant gene in question,
prepare good copies of that gene, then deliver them to patients'
cells. The hope was that the treated cells would give rise
to new generations of healthy cells for the rest of the patient's
life. The concept was elegant, but would require decades of
research to locate the genes that cause illnesses.
1990, it was working in the lab. By inserting healthy genes
into cells from CF patients, scientists were able to transmogrify
the sick cells as if by magic into healthy cells.
W. French Anderson and his gene therapy patient Ashanti
same year, four-year-old Ashanti DeSilva became the first
person in history to receive gene therapy. Dr. W. French Anderson
of the National Heart, Lung and Blood Institute and Dr. Michael
Blaese and Dr. Kenneth Culver, both of the National Cancer
Institute, performed the historic and controversial experiment.
suffered from a rare immune disorder known as ADA deficiency
that made her vulnerable to even the mildest infections. A
single genetic defect- like a typo in a novel- left DeSilva
unable to produce an important enzyme. Without that enzyme,
DeSilva was likely to die a premature death.
Anderson, Blaese and Culver drew the girl's blood and treated
her defective white blood cells with the gene she lacked.
The altered cells were then injected back into the girl, where-
the scientists hoped- they would produce the enzyme she needed
as well as produce future generations of normal cells.
the treatment proved safe, its efficacy is still in question.
The treated cells did produce the enzyme, but failed to give
rise to healthy new cells. DeSilva, who is today relatively
healthy, still receives periodic gene therapy to maintain
the necessary levels of the enzyme in her blood. She also
takes doses of the enzyme itself, in the form of a drug called
PEG-ADA, which makes it difficult to tell how well the gene
therapy would have worked alone.
was a very logical approach," says Dr.
Jeffrey Isner, Chief of Vascular Medicine and Cardiovascular
Research at St. Elizabeth's Medical Center in Boston as well
as Professor of Medicine at Tufts University School of Medicine.
"But in most cases the strategy failed, because the vectors
we have today are not ready for prime time."
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Photo: Dr. W. French Anderson