NEW YORK (Reuters) - U.S. medical
advisers are considering whether there is scientific justification for
allowing human studies of a controversial procedure known as
"three-parent in vitro fertilization (IVF)," a technique supporters say
could prevent horrific genetic defects but that critics believe could
lead to designer babies.
During two days of public hearings starting on Tuesday, scientists
were scheduled to present their research to outside advisers to the U.S.
Food and Drug Administration. The agency will decide whether safety
concerns raised by three-parent IVF are minimal enough to allow clinical
trials to begin.
The committee is focusing only on the science, and at the end of
Tuesday's hearing some committee members expressed concern that animal
research cannot yet show that human studies would be safe for women and
any children born via the three-parent technique.
Several panelists felt "there was probably not enough data in
animals . . . to move on to human trials without answering a few
additional questions" about safety, said committee chairman Dr. Evan
Snyder of the Sanford/Burnham Medical Research Institute in La Jolla,
California, in summarizing their views at the end of Tuesday's session.
Although the panel has not been asked to consider legal or ethical
issues, members of the public focused on those. Speakers warned the
panel that use of three-parent IVF "could alter the human species,"
represented "an unprecedented level of experimentation on non-consenting
human subjects" (meaning any children born via the technique), and
"could open the door to genetically modified children" who would be
"manufactured products."
In the three-parent procedure, one man would donate sperm and all
its DNA for in-vitro fertilization. The would-be biological mother would
contribute the egg and most of its DNA. But if the mother carries
harmful genetic mutations in cellular structures called mitochondria,
scientists would remove her unhealthy mitochondria and substitute those
of a second woman so the baby would not inherit a potentially
devastating "mitochondrial disease."
Allowing such procedures "would produce genetically modified human
beings," Marcy Darnovsky, executive director of the Berkeley,
California-based Center for Genetics and Society, a non-profit that
focuses on genetic and reproductive technologies, told the committee.
If the FDA allows clinical trials, she warned, it would introduce "a
regime of high-tech consumer eugenics" and represent "the first time a
government body had okayed genetic changes for humans and their
descendants."
Although the FDA committee is considering only scientific issues,
such as whether animal research can show mitochondrial manipulation is
safe or not, the agency said it is prepared to go beyond that.
"We have heard the concerns expressed at the advisory committee
meeting, and will take the information back to consider whether we need
to facilitate a public discussion and, if so, how best to do this,"
spokeswoman Jen Rodriguez told Reuters.
PREVENTING DISEASE
Some human eggs contain mutations in little-known genes inside
mitochondria, which are structures that produce energy, fight viruses
and perform other crucial functions in all cells.
Scientists have identified about
700 mutations in mitochondrial DNA that cause what Dr. Salvatore DiMauro
of Columbia University described to the FDA panel as "a Pandora's box
of diseases," including recurrent strokes, seizures, blindness,
deafness, diabetes, and a brain-destroying illness called necrotizing
encephalopathy.
Mitochondrial disease cannot be diagnosed prenatally, DiMauro said.
In the United States, biologist Shoukhrat Mitalipov of Oregon Health and
Science University told the committee that up to 4,000 children per
year are born with inherited mitochondrial mutations. Mitochondrial
diseases, he added, are incurable.
That has spurred research on how to strip out mitochondria with genetic mutations and replace them with healthy mitochondria.
One technique, pioneered at Newcastle University in England, starts
with a fertilized egg whose mitochondria contain mutations. Scientists
remove the embryo-to-be's genome, also called nuclear DNA. This DNA is
then injected into an egg from a second woman whose mitochondrial DNA is
healthy and whose own nuclear DNA has been removed. Result: a
fertilized egg with healthy mitochondria and its parents' nuclear DNA.
Another technique, called maternal spindle transfer, starts with an
unfertilized egg from a woman with mitochondrial mutations, explained
Oregon's Mitalipov, who has used the technique in monkeys and said it is
ready for human trials. The egg's genome is removed and injected into a
healthy egg whose own genome has been removed. The egg, with standard
DNA from the mother-to-be and mitochondrial DNA from the egg donor, is
then fertilized with the would-be father's sperm.
Last year, British health authorities announced that they would
draft regulations for three-parent assisted reproduction. The
regulations have yet to be issued and would require the consent of
Parliament to be implemented.
Although some opponents of mitochondrial manipulation raise the
specter of genetic engineering, replacing mutation-filled mitochondria
with healthy ones would not be genetic engineering in the usual
understanding of the term. It would not make a child smarter, more
athletic, more attractive, or otherwise different from what his genome
and environment would otherwise produce.
The phrase "designer babies conjures up the wrong message," panel
member John Gearhart, a stem-cell scientist at the University of
Pennsylvania School of Medicine, said in discussing media coverage of
the issue. "That leads to a complete misunderstanding on the part of the
public of what this is all about."
The FDA has authority over any clinical trials of mitochondrial
manipulation as part of its mandate to protect human research subjects,
which in this case includes women and any children born from the
procedure.
For over a decade, the FDA has
forbidden production of three-parent embryos in humans without its
explicit permission. In 2001, researchers combined ingredients from
healthy eggs with the eggs of infertile women and fertilized the merged
ova with sperm. Just over a dozen live births resulted, but since then
under the FDA ban U.S. scientists have used the techniques only on mice,
monkeys, cows and other animals
Pradeep Kumar Shukla
PGDM 2 SEM
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