Two-year results released
from Tysabri
clinical trial
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Summary
Biogen Idec and Elan Corporation announced the successful completion
of a two-year trial of Tysabri® (natalizumab,
formerly known as Antegren) as a treatment for relapsing
forms of MS. According to a company news release, the study
(known as AFFIRM) achieved its primary outcome by slowing
the risk of progression of disability by 42 percent.
The release also confirmed that the drug
reduced the rate of clinical relapses by 67% over two years,
and continued to reduce the development of new or newly enlarging
MRI-detected brain lesions, findings that are consistent with
the previously released results of the first year of the trial.
(See December 10, 2004 Medical Update Memo FDA
approves natalizumab (Tysabri® - formerly known
as Antegren) for relapsing forms of MS) . Progression
of disability was assessed using the EDSS (Expanded Disability
Status Score), which measures walking ability and other neurologic
function.
The companies have announced that details
of the two-year AFFIRM results will be presented at the American
Academy of Neurology meeting in April, and that the two-year
data will be submitted to the regulatory agencies such as the
FDA in the United States and Health Canada.
Details
According to the companies, the safety
profile of Tysabri over two years was consistent with findings
announced for the first year. Common side effects included
headache, fatigue, urinary tract infection, depression, lower
respiratory tract infection, limb and joint pain and sore
throat. The overall incidence of infection was similar between
those on Tysabri and those on placebo. Serious infections,
such as pneumonia and urinary tract infection, occurred in
3.2 percent of participants on therapy and in 2.6 percent
on inactive placebo. Tysabri has been associated with hypersensitivity
reactions, including serious systemic reactions that occurred
at an incidence of less than 1 percent of patients in the
trial. Longer term safety information is not available.
The AFFIRM trial was placebo-controlled
and involved 942 participants from around the world. In November
2004, the U.S. Food and Drug Administration approved Tysabri
for relapsing forms of MS based on first-year results of
the AFFIRM trial and of a second trial called SENTINEL, which
adds Tysabri to Avonex® (interferon beta-1a)
therapy. The companies expect results from the SENTINEL trial
by mid year.
Unlike other drugs that have already
been approved for treating MS, Tysabri is a monoclonal antibody
that is given by infusion into a vein every four weeks. It
is designed to interfere with movement of potentially damaging
immune cells from the bloodstream, across the “blood-brain
barrier,” and into the brain and spinal cord. Tysabri
inhibits this movement by attaching to alpha 4-integrin,
a protein on the surface of immune T cells that normally
enables them to pass through the blood-brain barrier.
Tysabri is currently under priority review
by Health Canada with a decision anticipated later this year.
The fact that Tysabri has been shown to
be safe and effective over two years against both relapses
and progression is very good news for people with MS. The MS
Society of Canada is closely monitoring the therapy’s
review status and looks forward to a positive decision from
Health Canada as soon as possible.
Biogen Idec Canada has made available an information line in
English and French for further inquiries about Tysabri (natalizumab):
1-877-674-6365.
(With information courtesy, National MS
Society [USA])
ASK MS Information System Code:
1.4.1.60.5.e
Disclaimer
The Multiple Sclerosis Society of Canada is an independent, voluntary health
agency and does not approve, endorse or recommend any specific product or therapy
but provides information to assist individuals in making their own decisions.
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