A drug commonly used to slow the loss of central
vision has shown promise in stemming a common precursor of
blindness in diabetics, which involves the same central
light-sensitive area of the retina,
Johns Hopkins Wilmer
Eye Institute scientists report.
Encouraged by the effect of ranibuzumab in people with
macular degeneration, the Johns Hopkins researchers
injected the drug into the eyes of 10 people losing their
sight from macular edema, one of many complications of
diabetes and a first stage of diabetic retinopathy.
Over the course of several months of therapy, every
patient in the preliminary Johns Hopkins study could read
at least two more lines on the standard eye chart, the
researchers said. Moreover, the thickness of the patients'
maculae, the central part of the retina responsible for
seeing fine details, decreased an average of 85 percent.
The American Journal of Ophthalmology published the
team's findings in the December issue.
Quan Dong Nguyen, an assistant professor of
ophthalmology at the Wilmer Eye Institute, said, "The
results are impressive, although we will not know until we
begin a larger clinical trial what the long-term benefits
of the drug might be."
The Johns Hopkins group believes that ranibuzumab
interferes with a protein that spurs the growth of unwanted
blood vessels in the back of the eye. Vascular endothelial
growth factor, or VEGF, is released when the oxygen supply
in the eye is restricted by blood vessel damage related to
diabetes.
In a self-preserving attempt to acquire more oxygen,
the VEGF signals for the creation of new blood vessels,
which almost always damage vision, rather than improve it,
by blocking light's entry onto the retina.
"We've suspected for a while that ranibuzumab's
ability to shut down VEGF's signaling would do the trick
because it's highly likely that VEGF is the culprit when it
comes to diabetic macular edema," Nguyen said.
More than 4 million diabetics in the United States
have diabetic retinopathy, and, according to the National
Eye Institute, one in 12 of those experience at least some
vision loss.
Macular edema, a first stage of retinopathy, occurs
when, over time, excess uncontrolled blood sugar damages
the tiny blood vessels in the eye, causing fluid and fat to
leak onto the retina at the back of the eye. The swelling
interferes with focus and blurs vision. Making matters
worse, a lack of oxygen often then triggers VEGF's
production cycle.
All 10 subjects in the study had some vision loss at
the start of the clinical trial, in which ranibuzumab was
administered at the one-, two-, four- and six-month marks.
The thickness of each patient's macula was measured at each
point in the study using an advanced digital imaging
technique.
"Within a week, several patients experienced dramatic
reductions in the thickness of their maculas, and there
were further improvements with each injection," said Peter
Campochiaro, the Dolores and George Eccles Professor of
Ophthalmology at the School of Medicine, who is also an
investigator in the study.
Ranibuzumab is marketed for treatment of neovascular
macular degeneration by Genentech under the brand name
Lucentis.
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