Warren G can navigate through
his home blindfolded. This may seem like a strange skill
but it's a necessary one. Warren is 57 and was diagnosed
with wet age-related macular degeneration (ARMD) a year
ago. His disease hasn't responded well to therapy and
he's desperate for another option that will improve his
sight. Thanks to a recent study, he may get his wish.
Several decades ago, it was suggested
that ischemia in the aging retina was stimulating some
unknown growth factor that in turn led to new vascularization.
After much painstaking research, the culprit was identified
as vascular endothelial growth factor (VEGF). Now, the
first trial of a drug designed to block VEGF in the
eyes has reported its results in the December 30 issue
of the New England Journal of Medicine (NEJM).
Pegaptanib, the researchers say, proved an "effective
therapy for neovascular age-related macular degeneration."
A week before publication, the drug received FDA approval.
It will be marketed under the brand name Macugen.
STICK
A NEEDLE IN MY EYE
Two clinical trials, totalling 1,208 patients, were
held at 117 sites in the US, Canada, Europe, Israel,
Australia and South America. Treatments were administered
by injection directly into the eye. Patients received
pegaptanib in either 0.3mg, 1mg, or 3mg doses, while
the control group received sham injections of placebo.
In the end, the lowest dose proved just as effective
as the larger ones.
In the lowest dose group, 70% of
patients lost fewer than 15 letters of visual acuity
after 54 weeks, compared to 55% of patients in the sham
injection group. Ten percent of the low-dose pegaptanib
patients lost 30 letters or more, compared to 22% of
the sham injection group. A third of the pegaptanib
patients either lost no visual acuity or actually improved,
compared to 23% in the placebo group.
The commonest adverse events were
endophthalmitis (in 1.3% of patients), traumatic injury
to the lens (in 0.7%), and retinal detachment (in 0.6%).
One patient out of the 904 pegaptanib patients suffered
a severe loss of vision as a result of treatment. The
researchers acknowledged that pegaptanib's longterm
safety is uncertain.
A
BETTER OPTION?
Various media sources hailed pegaptanib as a revolutionary
breakthrough in the treatment of wet ARMD, but FDA acting
commissioner Mr Leslie Crawford was more circumspect.
Noting that the drug "is among the first treatments
to target the underlying biology of wet age-related
macular degeneration," he described it as "a needed
addition to the treatment of patients with this disease."
That assessment was shared by Dr
Frederick Ferris of the National Institutes of Health.
He compared the new treatment to photodynamic therapy
- a recent treatment in which an infrared laser activates
a photosensitive drug in the retina. In a commentary
accompanying the NEJM study he points out that
"unfortunately, the magnitude of the treatment effect
in reducing the risk of visual loss is similar to that
seen with photodynamic therapy and, as with photodynamic
therapy, only about 10% of patients can anticipate improvement
in their vision."
Why then, he asked "is there such
general enthusiasm for it? It is because we now have
more than one way of attacking neovascularization, and
thus may have the opportunity to test combinations of
treatments, similar to the successful approaches used
for various cancers."
Several other anti-VEGF treatments
are now in the pipeline, and sufferers of dry ARMD can
also look forward to new treatments. The Mississauga-based
company OccuLogix Inc this week began a 12-month trial
of its blood filtering process known as rheopheresis,
aimed at stopping progression of the dry form of the
disease. An FDA decision is expected sometime in 2006.
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