Scientists say they have used the gene editing tool CRISPR
inside someone's body for the first time, a new frontier for efforts to operate
on DNA, the chemical code of life, to treat diseases.
A patient recently had it done at the Casey Eye Institute at
Oregon Health & Science University in Portland for an inherited form of
blindness, the companies that make the treatment announced Wednesday. They
would not give details on the patient or when the surgery occurred.
It may take up to a month to see if it worked to restore
vision. If the first few attempts seem safe, doctors plan to test it on 18
children and adults.
“We literally have the potential to take people who are
essentially blind and make them see,” said Charles Albright, chief scientific
officer at Editas Medicine, the Cambridge, Massachusetts-based company
developing the treatment with Dublin-based Allergan. “We think it could open up
a whole new set of medicines to go in and change your DNA.”
Dr. Jason Comander, an eye surgeon at Massachusetts Eye and
Ear in Boston, another hospital that plans to enroll patients in the study,
said it marks “a new era in medicine” using a technology that “makes editing
DNA much easier and much more effective.”
Doctors first tried in-the-body gene editing in 2017 for a
different inherited disease using a tool called zinc fingers. Many scientists
believe CRISPR is a much easier tool for locating and cutting DNA at a specific
spot, so interest in the new research is very high.
The people in this study have Leber congenital amaurosis,
caused by a gene mutation that keeps the body from making a protein needed to
convert light into signals to the brain, which enables sight. They're often
born with little vision and can lose even that within a few years.
Scientists can't treat it with standard gene therapy --
supplying a replacement gene -- because the one needed is too big to fit inside
the disabled viruses that are used to ferry it into cells.
So they're aiming to edit, or delete the mutation by making
two cuts on either side of it. The hope is that the ends of DNA will reconnect
and allow the gene to work as it should.
t's done in an hour-long surgery under general anesthesia.
Through a tube the width of a hair, doctors drip three drops of fluid
containing the gene editing machinery just beneath the retina, the lining at
the back of the eye that contains the light-sensing cells.
"Once the cell is edited, it’s permanent and that cell
will persist hopefully for the life of the patient," because these cells
don't divide, said one study leader not involved in this first case, Dr. Eric
Pierce at Massachusetts Eye and Ear.
Doctors think they need to fix one tenth to one third of the
cells to restore vision. In animal tests, scientists were able to correct half
of the cells with the treatment, Albright said.
The eye surgery itself poses little risk, doctors say.
Infections and bleeding are relatively rare complications.
One of the biggest potential risks from gene editing is that
CRISPR could make unintended changes in other genes, but the companies have
done a lot to minimize that and to ensure that the treatment cuts only where
it's intended to, Pierce said. He has consulted for Editas and helped test a
gene therapy, Luxturna, that's sold for a different type of inherited
blindness.
Some independent experts were optimistic about the new
study.
“The gene editing approach is really exciting. We need
technology that will be able to deal with problems like these large genes,”
said Dr. Jean Bennett, a University of Pennsylvania researcher who helped test
Luxturna at the Children’s Hospital of Philadelphia.
In one day, she had three calls from families seeking
solutions to inherited blindness.
“It’s a terrible disease," she said. "Right now
they have nothing.”
https://www.nytimes.com/aponline/2020/03/04/health/ap-us-med-genetic-frontiers-gene-editing-blindness.html?searchResultPosition=1
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