Gene therapy disappoints so far, U.S. experts say
RTw 25.09.97 03:40
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By Maggie Fox, Health and Science Correspondent
WASHINGTON, Sept 24 (Reuter) - Efforts at using gene therapy to
treat sick people have been disappointing so far but are worth
pursuing, experts said on Wednesday.
Despite newspaper headlines, millions of dollars poured into
research and a lot of raised hopes, not a single person has been
cured by giving them new, healthy genes, they told a conference.
"The long and short of it is that we have not achieved gene
therapy," said Theodore Friedmann, director of the human
gene therapy program at the University of California in San
Diego.
"It's clear that most therapies for genetic diseases are
ineffective," Friedmann told a seminar sponsored by the
American Association for the Advancement of Science.
Nonetheless, Friedmann and other experts said they firmly
believed gene therapy would happen. "We should have an
enlightened public debate while the issue is still remote,"
he said. "It's fiction now, but it won't be for long."
He said polls showed strong support for using gene therapy to
treat disease, and even for gene enhancement.
But while transgenic animals containing human and other genes had
been created and even bred, work on humans was much slower, and
rightly so.
"Humans are not mice. One cannot breed humans like mice.
With mice one can just put mistakes away -- with humans, one
cannot," Friedmann said.
Malcolm Brenner, director of the gene therapy program at St
Jude's Children's Research Hospital in Memphis, Tennessee, said
it was not surprising that the 400 clinical research protocols
under way into gene therapy had produced little.
Gene therapy was difficult, he said. First the faulty gene or
genes had to be identified. Then the new gene had to be targeted
to the nucleus of the right cell, and it would have to hook up
with the cell's DNA in just the right place.
The perfect vector, or vehicle for carrying the gene, had not
been found. Viruses were hard to control, while liposomes --
essentially cases made of fats -- did not last long.
Then the gene's product -- all genes "code" for
production of a protein -- would have to be regulated.
"I don't think any of the vectors we have now are anywhere
close to achieving this," Brenner said.
So far gene therapy, even when it did work, affected only a tiny
proportion of the cells in the human body, he added.
Yet people wanted to believe in gene therapy.
Cystic fibrosis was an example of a gene therapy experiment that
was "greeted with enormous -- I think absurd -- hype,"
Brenner said.
Doctors hoped cystic fibrosis would be an easy first target. It
is caused by one gene and many of its effects are seen in the
lungs, which are easy to reach with inhaled drugs or drips.
One effect of cystic fibrosis is the buildup of mucus and
frequent lung infections. Researchers thought adenoviruses, a
family that included cold and flu viruses, was appropriate to
carry genes to the lungs.
But instead, Brenner said, the adenoviruses caused inflammation
and in some cases worsened the condition.
Nevertheless, Brenner said, scientists had to keep trying.
"It hasn't cured anybody yet but it has helped some
patients," he said. For example, his team inserted a gene
for interleukin-2 -- an immune system product that acts against
tumors -- into children with the childhood cancer neuroblastoma.
The tumors were definitely affected. "I still believe it is
very much worth exploring the area," Brenner said. REUTER