A front-line
drug against multiple sclerosis (MS) has recently
passed a long-anticipated, critical test of its
effectiveness, according to a report in the March
2001 issue of Annals of Neurology, the research
publication of the American Neurological
Association. Brain scans of patients taking
glatiramer acetate (GA), sold in the United States
as Copaxone, indicate that the drug significantly
curtails the number of new brain lesions
(injuries) caused by flare-ups of the disease and
reduces the overall volume of damaged brain
tissue.
Multiple sclerosis is a disorder of the nerve
fibers of the brain and spinal cord. In MS,
scarring (sclerosis) replaces myelin, a substance
that normally surrounds the nerves and speeds
electrical conduction through the fibers.
Depending on which nerve fibers are hindered,
patients can experience problems ranging from
weakness and clumsiness to numbness, visual
disturbances, and even emotional and intellectual
alterations. In some patients, MS manifests itself
in cycles of relapse and remission; in other
patients, the disease may progress to a stage of
severe debilitation.
Although the cause of MS is not known, most
circumstantial evidence has suggested that it is
an autoimmune disorder wherein the immune system's
defense mechanisms erroneously destroy the myelin.
Interferon-beta and GA, two drugs that act very
differently on the immune system, both reduce the
frequency of MS relapses by approximately 30%.
Unlike interferon-beta, however, GA is a treatment
specific for MS and has the advantage of not
causing major side effects, such as the flu-like
symptoms and depression that have been associated
with interferon-beta.
Up until now, one key outcome measure--magnetic
resonance imaging (MRI)--was missing for GA,
however. MRI allows researchers to measure the
number and volume of the lesions that accumulate
in the brains of MS patients and is used to
evaluate the effects of new treatments. This
technique has demonstrated clearly the positive
effects of interferon-beta but has never been used
to test the effects of GA.
In the current study, 239 patients with
relapsing/remitting MS were enrolled from 29
medical centers in six European countries and
Canada. Half of the patients received daily GA
injections and half were given a placebo substance
for nine months. The researchers used monthly MRI
scans to examine the subjects' brains for evidence
of new lesions.
Glatiramer acetate had a significant effect in
reducing the activity of the disease, as measured
by the appearance of new lesions. The drug also
significantly reduced the burden of the disease,
as measured by the volume of the damaged tissue.
A secondary objective of the study was to
determine the time course of the protective
effect. The researchers found that the therapeutic
effects of GA, both in terms of preventing
relapses and protecting the brain, appeared three
to four months after initiation of the treatment.
This observation confirms scientists' prior
understanding of how GA exerts its influence - by
gradually inducing the immune system to protect,
rather than to destroy, brain tissue.
