— For the more than 10 million Americans with
colorblindness, there’s never been a treatment, let alone a
cure, for the condition that leaves them unable to distinguish
the first time, two University of Washington professors have
teamed with a California biotech firm to develop what they say
may be a solution: a single shot in the eye that reveals the
world in full color.
Maureen Neitz, husband-and-wife scientists who have studied
the vision disorder for years, have arranged an exclusive
license agreement between UW and Avalanche Biotechnologies of
Menlo Park. Together, they’ve found a new way to deliver
genes that can replace missing color-producing proteins in
certain cells, called cones, in the eyes.
don’t think there’s any question that it will work,"
said Maureen Neitz, 57, a UW professor of ophthalmology.
treatment — which may be tested in humans within two years
— could be a boon for the 1 in 12 men and 1 in 230 women
with color-vision deficiency.
trouble occurs when people are born without one or more of the
three types of color-sensing proteins normally present in the
cones of the retina. The most common type is red-green
colorblindness, followed by blue-yellow colorblindness. A very
small proportion of the population is completely colorblind,
seeing only shades of gray.
they can’t perceive certain colors, they see hues in muted
or different shades than people with normal vision.
Chandler, 38, of Seattle, said he first noticed he was
colorblind in seventh grade, when he started getting C’s and
D’s on drawings in science class.
was coloring green stuff brown and brown stuff green,"
recalled Chandler, a traffic-safety engineer.
is often a genetic disorder. It affects mostly men, who can
inherit a mutation on the X chromosome that impairs their
perception of red and green. A much smaller fraction of cases
are in women, who have two X chromosomes, which gives them a
better chance of avoiding effects of any genetic defect.
people think of colorblindness as an inconvenience or mild
disability, mainly causing problems with unmatched shirts and
socks. But the Neitzes say the condition can have profound
impacts — limiting choices for education or careers, making
driving dangerous, and forcing continual adaptation to a world
geared for color vision.
are an awful lot of people who feel like their life is ruined
because they don’t see color," said Jay Neitz, 61, the
professor of ophthalmology who confirmed in 1989 that dogs are
may not qualify as commercial pilots, for instance, if they’re
colorblind. Other careers that can be limited include those of
chefs, decorators, electricians and house painters, all of
which require detailed color vision.
Neitzes have focused on the disorder for years, first proving
in 2009 they could use gene therapy to correct colorblindness
in male squirrel monkeys, which are born unable to distinguish
between red and green.
journal Nature, they reported the success of a technique that
inserted the human form of a gene that detects red color into
a viral shell, and then injected it behind the retinas of two
monkeys, named Sam and Dalton — the latter after the British
chemist John Dalton, who was the first to analyze and report
on his own color-vision deficiency — had been trained to
recognize colors on a computer screen in exchange for a reward
of grape juice. Before the surgery, they couldn’t detect
certain hues, while after the procedure they got them right
nearly every time.
technique is risky, requiring surgery, so the Neitzes were
looking for another way to do the job.
10 years, we have been trying to figure out a way to get the
genes to go to the back of the eye with a simple shot,"
with the help of Avalanche, the researchers say they’ve
developed a technique that does just that. It uses a safe
vector, called an adeno-associated virus, to house the pigment
gene, which is injected directly into the vitreous, the
jellylike center of the eye. Once, there, it targets cells on
the back of the retina, said Thomas W. Chalberg Jr., the
co-founder and chief executive of the firm.
a protein shell, kind of like a Trojan horse, that gets you
entry into the cell. Once you’re there, the DNA gets to set
up shop and produce the photo pigment of interest," he
said. Avalanche has two drug candidates, AVA-322 and AVA-323,
that carry pigment-producing genes.
only 30 percent of the cells to be transduced, or changed, to
put the world in a whole new hue, Jay Neitz said. Early tests
show the technique meets that mark in monkeys.
preclinical trials are complete, Chalberg said he hopes to
move to human trials within one to two years and then seek
federal Food and Drug Administration approval for the
treatment. Eventually, the treatment could be offered during a
single visit to an opthalmologist’s office.
development would be "an amazing advantage," said
Dr. Rohit Varma, a professor of ophthalmology and director of
the Eye Institute at the University of Southern California,
who is not involved in the research.
would cure or at least help people who are colorblind,"
he said. "This is the first hope, in many ways, for these
individuals that suffer from this."
noting that many tests that succeeded in animals have later
failed in humans, he said he’s cautiously optimistic that
the trials will deliver as promised. Plus, he said, it will be
important to learn whether the therapy not only adds the
color-sensing ability, but actually improves the lives of
those who are treated.
a thought echoed by Dr. Paul Sternberg Jr., chairman of the
Vanderbilt Eye Institute at Vanderbilt University in Nashville
and a clinical spokesman for the American Academy of
Ophthalmology. He called the Neitzes "world-class
scientists" and said the wider field awaits potential
human trials of the technique.
brain develops a certain way of seeing," he said.
"We don’t know whether replacing the visual pigment in
a 25-year-old colorblind man will allow him to see in full
there appears to be high interest in finding out. Since March
25, more than 10,000 people have visited a new website
associated with the project, ,
including many who hope to be the first cured of the
definitely would be interested," said David Curry, 33, of
Port Townsend, Wash., who had to abandon a dream of becoming a
commercial helicopter pilot because of his deuteranopia, or
red-green colorblindness. "I’d want to speak to
Professor Neitz more and learn about the process more before
putting my eyes on the chopping block, so to speak. But I’ve
always wondered what it would look like to see color like
Chandler, also colorblind, isn’t so sure. He said he’s
learned to adapt to the world using cues other than color to
have mixed feelings about ‘curing’ my color-vision
deficiency," said Chandler. "On one hand, I’m
nervous about the change, since I’ve seen like this my
entire life. On the other, it would potentially be exciting to
see things I had not seen before."
their part, the Neitzes say they’re eager to see a lifetime
of work put into clinical practice. The technique to correct
colorblindness also might eventually be used for other
cone-based disorders, including retinitis pigmentosa, an
inherited disorder that can lead to blindness.
colorblindness, though, could affect millions who would like
to know what they’re missing, the scientists said.
nobody with a black-and-white TV who, if you said, ‘Would
you like color TV?’ wouldn’t trade it," Jay Neitz