Drug Therapy
Anti-angiogenic drug therapy has become the primary treatment for wet
AMD and is considered far more effective than previous therapies.
Usually injected into the eye, these drugs have been developed to halt
the growth of abnormal blood vessels in the macula to stabilize or even
improve vision.
The anti-angiogenic
drugs described below block a protein called vascular endothelial growth
factor, or VEGF (pronounced vej-ef). Growth factors like VEGF encourage
abnormal blood vessels to proliferate. These agents block VEGF so that
eye cells no longer receive the message to make new blood vessels.
Lucentis (ranibizumab):
This
drug, produced by Genentech, was approved by the U.S. Food and Drug
Administration in June 2006. After one year of treatment, nearly all
patients treated with Lucentis in Phase III clinical trials maintained
their vision at or near their initial visual acuity. Approximately
one-third of study participants experienced improved vision by at least
three lines (or 15 letters) on the study eye chart.
Some people
don’t respond well to Lucentis, although it is not clear why.
A clinical
trial sponsored by Genentech
is being conducted to learn if underlying genetic factors play a role.
Researchers will study the patients’ response to treatment and analyze
their DNA. These findings may lead to the development of medications
personalized to the patient’s own gene structure.
Avastin (bevacizumab):
Initially approved as a systemic treatment for advanced colorectal
cancer, this drug is closely related to Lucentis and is made by the same
company. Since mid-2005, Avastin has been widely used for wet AMD.
Initial results are promising, with many investigators reporting
short-term efficacy and safety results comparable to those obtained with
Lucentis. A new
multicenter clinical trial sponsored by the National Eye Institute (NEI)
will compare Avastin and Lucentis for the treatment of AMD.
The first formal study of Avastin as an AMD therapy, it
is
expected to answer questions about the drug’s long-term safety
and effectiveness.
Macugen (pegaptanib):
This was
the first anti-VEGF drug for AMD to be approved by the FDA. Macugen
appears to be less effective than Lucentis and Avastin and consequently
has a very limited role in the treatment of wet AMD.
Photodynamic
Therapy (PDT)
Until the advent of anti-angiogenic
medications, photodynamic therapy – or PDT – has been the primary
treatment for wet AMD. The technique consists of injecting a light
activated drug (vereporfin or Visudyne) before the application of a
special type of laser energy. The drug passes through and is retained by
the abnormal vessels in the eye, absorbing the laser energy and closing
the vessels. The goal is to destroy the unwanted new blood vessels
without harming the surrounding tissues. With the availability of drug
therapy, PDT is not used as commonly as in the past, although it
continues to play a role in the treatment of wet AMD.
In
certain cases, PDT is combined with intraocular injections of the
steroid medication triamcinolone. Some studies show improved outcomes
with this combination over PDT alone. However, intraocular steroids are
associated with side effects in some individuals, including glaucoma and
cataract formation.
Laser Therapy for Wet AMD
For more than 20 years,
conventional laser therapy (usually employing an argon laser) was the
only proven effective therapy for wet AMD. However, its effects were
limited and the number of cases eligible for treatment was small. Newer
methods of treatment using drug therapy and photodynamic therapy are now
indicated for most patients with wet AMD. There remains, however,
certain selected cases for which laser may be appropriate.
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