Improving A Life - Rare Disorder Responds to Gene Therapy
By CZERNE M. REID - [log in to unmask]

"The group plans to extend its methods to treating more common
neurodegenerative disorders such as Alzheimer's, Parkinson's and Tay-Sachs."

Posted: July 25, 2004

Four-year-old Ashtyn Fellenz cannot sit up or raise her head or talk. And she "eats"
only through a tube attached to her stomach. The Menomonee Falls girl has a rare
genetic brain disorder known as Canavan disease.

Ashtyn is one of only 21 participants from the United States, Europe and South
America in an enterprising clinical trial where researchers pump genes into the
brain in hopes of improving motor skills and brain function.

A floppy head and stiff limbs are trademarks of the disorder. Other symptoms
include mental retardation, blindness, deafness and paralysis.

Chemical builds up

In Canavan disease, a malfunctioning gene causes a buildup in the brain of a
chemical called N-acetyl aspartate. The gene fails to produce a protein responsible
for breaking this substance down into the building blocks of the brain's white matter.

Also called myelin, white matter is a fatty layer that coats nerves in the brain and
spinal cord. It transmits nerve impulses from the brain to other cells in the body. In
Canavan disease, the white matter becomes spongy and full of tiny fluid-filled holes.

Children with the disease usually die by age 4, but in rare cases could live into their
20s, according to the National Institute of Neurological Disorders and Stroke.

The clinical trial - which began in April 2003 and will run through summer 2005 - is
testing how gene therapy can improve the odds for children with Canavan disease.

"This is a first step; the potential down the road for a cure is a real one," said
Christopher Janson, principal investigator of gene therapy for Canavan disease at
Cooper Hospital, a branch of the University of Medicine and Dentistry of New
Jersey. Researchers from Robert Wood Johnson Medical School - another branch
of the same university - and Children's Hospital of Pennsylvania are also part of the
team. The group plans to extend its methods to treating more common
neurodegenerative disorders such as Alzheimer's, Parkinson's and Tay-Sachs.

Eight years ago, in New Zealand, the same group performed the first gene therapy
treatment of a genetic brain disorder on children with Canavan disease. This work
ruffled some feathers within the gene-therapy field because the investigators tested
the method on humans without first showing that it was effective in animals.

At the time, they delivered genes surgically, using a fat-based molecule to shuttle
genes to the brain.

These days, the team delivers genes using a different kind of brain surgery as well
as a new vehicle - an adeno-associated virus.

But some gene-therapy experts remain cautious because no researchers have
successfully used that kind of delivery method in humans.

Adding to the uncertainty, in late May, California-based Avigen Inc. - a company
that develops gene-therapy products - yanked its support from a hemophilia gene
therapy trial that used this type of delivery to supply genes to the liver. Two of
seven patients in the study - conducted at Stanford University, Children's Hospital
of Pennsylvania and University of Pittsburgh - developed mild liver trouble. The
researchers feared the toxicity might interfere with the treatment, said Mark Kay,
one of the trial's scientific advisers based at Stanford. Test animals had not shown
any liver damage.

"You can't always predict what will happen in humans even if you have the best
animal studies," Kay said.

The Canavan disease researchers are unfazed. Immune responses to a virus used
in the liver do not necessarily forecast what will happen when the virus is used in
the brain. Indeed, in the Canavan disease trial, tests of blood serum and spinal fluid
show that there is little immune response to the virus or to the gene's protein
products, Janson said.

Furthermore, the difference in gene delivery method between the two trials will also
affect the results, said Paola Leone, co-principal investigator of the Canavan
disease trial. In the hemophilia trial, the virus was administered to an artery and
transported through the bloodstream to the liver. In the Canavan disease trial, the
virus was injected directly into the brain.

"If they demonstrate that it is effective in Canavan, it would be a remarkable result,"
said Roscoe Brady, chief of the developmental and metabolic neurology branch of
the National Institute of Neurological Disorders and Stroke.

"Now we're comfortable that the risk is minimal, and we can think more about the
benefit side of the equation," said Janson. "We want to move a little more
aggressively."
How gene is delivered

To try to arrest deterioration of the brain's white matter, the researchers open a
patient's skull and drill six holes into the brain. Into each hole, they introduce a
catheter through which a pump slowly delivers a few drops of solution with about
900 billion viral particles containing the gene.

The viral particles make their way inside the brain's nerve cells, where they
disassemble, releasing the gene. The genes make copies of themselves and
produce the protein vital for white matter formation.

After the two- to three-hour surgery, the young patients in the trial typically stay in
the hospital for three days. Afterward, for at least 24 months, patients go for
frequent follow-up visits at Children's Hospital of Philadelphia. There, researchers
image the patients' brains to see if - over time - the harmful chemicals and water
levels in the brain decrease and some white matter is restored. They also monitor
responses such as changes in muscle tone and awareness level.

"It's a huge effort," said Leone.

Janson said he has seen a wide range of outcomes in patients, depending on their
age and the stage of the disease. While some patients did not show marked
improvement after treatment, others gained better control of their head and limbs,
and had improved sleep patterns, bowel movements and awareness levels.

"What we are seeing is the best effect that we can have," said Leone, considering
that the patients have already lost up to 40% of their brain mass.
Seeing progress

Since her gene therapy treatment one year ago, Ashtyn can now move her head
from side to side and even lift her arms and legs in ways she was unable to do
before. And her facial expressions have a brightness that wasn't there before, said
her nurse, Jacalyn Anderson.

Ashtyn has come a long way.

"She used to be just a rag doll," said Ashtyn's mother, Arlo Clark-Fellenz.

Ashtyn receives physical, occupational and music therapy for up to four days a
week at the School for Blind and Visually Impaired Children on Brown Deer Road.
Twice a month, she also has sessions with speech pathologist Rona Alexander who
treats children with feeding and swallowing difficulties.

First - with her hands and a small, gently vibrating rod - Alexander stimulates
Ashtyn's face, hands and mouth. This prepares the muscles to take on the task of
eating. Alexander waves tiny spoonfuls of chocolate pudding and yogurt under
Ashtyn's nose then places the food inside her mouth, while applying slight pressure
to Ashtyn's chin and lower lip. Ashtyn smiled after swallowing her pudding. Then
she took a small spoonful of water. "You did a great job today," Alexander told
Ashtyn.

The simple act of swallowing is a chore for children such as Ashtyn who have
Canavan disease, a disorder that affects mainly Ashkenazi Jews and people of
Saudi Arabian descent. Neither of Ashtyn's parents has a known Jewish or Saudi
Arabian heritage. Both parents must carry the culprit gene mutation for offspring to
have the disease. There is then a 1-in-4 chance a child will be born with the
disease. A simple prenatal blood test can reveal if a child is affected. Parents can
be screened to see if they are carriers of the defective gene that causes the
disease.

In the long term, Leone hopes to be able to do more than just stop the progress of
Canavan disease: She wants to reverse it. She is exploring the possibility of
replacing damaged brain cells with stem cells.

Although Ashtyn may not benefit from the proposed stem cell work, her physicians
and family are doing their best.

Clark-Fellenz said: "We all know that we have done our part to give her a full life."

SOURCE: Milwaukee Journal Sentinel, WI
http://www.jsonline.com/alive/well/jul04/245963.asp

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