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Questions and Answers on Tysabri
(natalizumab)
1. What is
natalizumab?
Natalizumab is a
monoclonal antibody that binds to a protein called
alpha-4-integrin. Integrins are found primarily on the surface of
white blood cells, and play a role in immune system activity.
2. What are monoclonal
antibodies?
Antibodies are naturally occurring
proteins produced by the immune system in response to foreign
substances. Once produced by the body, they recognize and bind to
specific proteins (antigens) on bacteria, viruses, and toxins, to
help the body fight disease.
Monoclonal
antibodies, such as natalizumab, are produced in cell culture
systems. They can be designed to bind to receptors on the body’s
normal cells. By recognizing and attaching to these receptors,
monoclonal antibodies can interfere with (or alter) normal or
abnormal cellular responses.
In this way, monoclonal antibodies may be useful in the treatment
of certain diseases.
3. What is
natalizumab used to treat?
Natalizumab is
approved to treat patients with relapsing forms of multiple
sclerosis to reduce the frequency of exacerbations. It was
approved based on results achieved after approximately one year of
treatment in ongoing controlled trials. These trials will continue
for another year. At this time, the safety and efficacy of
natalizumab beyond one year are not known.
Safety and
efficacy in patients with chronic progressive multiple sclerosis
have not been established.
4. What is multiple
sclerosis?
Multiple sclerosis (MS) is a
disease in which the immune system attacks the person's brain and
spinal cord. The disease causes a wide range of symptoms including
fatigue, difficulty walking, numbness, and vision problems.
5. What is relapsing MS?
This type of MS is characterized
by relapses (also known as exacerbations or attacks) during which
new symptoms can appear and old ones resurface or worsen. The
person fully or partially recovers from the deficits acquired
during the relapse. Relapses are followed by periods of remission,
during which no new symptoms occur.
6.
How does natalizumab work?
White blood cells are thought to
play a major role in causing the damage to the nervous system in
MS. Natalizumab binds to white blood cells and interferes with
their movement from the bloodstream into the brain and spinal cord
7. Is
natalizumab a cure for MS?
No, natalizumab will
not cure MS. In a study in which
patients were randomly assigned to
treatment with either natalizumab or placebo (an inactive
substance), natalizumab reduced the
average yearly relapse rate from 0.74 relapses per patient in the
placebo group, to 0.25 relapses per patient in the natalizumab
treated group. This is a relative reduction of 66%.
8.
What is accelerated approval?
Accelerated approval is a program the FDA developed to make
new drug products available for serious or life threatening
diseases when they appeared to provide a benefit over available
therapy (which could also mean there was no existing effective
treatment). Under this program, natalizumab is being approved on
the basis of early clinical study evidence (such as data from only
one year of study) suggesting that the drug is reasonably likely
to have a valuable effect on symptoms.
Several other
products are already available for the treatment of MS, including
Betaseron, Avonex, Rebif, Copaxone, and Novantrone. One of the
clinical studies with natalizumab was performed in patients
already being treated with Avonex. The addition of natalizumab
resulted in a further reduction in the occurrence of relapses,
beyond the benefit that those patients had already received from
Avonex.
The approval is granted on the condition that the manufacturer
must continue testing to demonstrate that the drug indeed provides
therapeutic benefit to the patient. If it does not, the FDA can
withdraw the product from the market more easily than usual.
9. How is
natalizumab given?
Natalizumab is
given by intravenous (in to a vein) infusion every four weeks.
10. What are
the possible side effects of natalizumab?
The most
frequently reported serious side effects with natalizumab are
infections, severe or life threatening allergic reactions,
depression (including thoughts of suicide) and gallbladder
problems. In the trials, these serious side effects occurred at a
rate of 0.8% for serious depression and gallbladder problems, at a
rate of 2.1% for serious infections.
Common side
effects include:
- Infections
- Headache
- Fatigue
- Depression
- Joint pain
- Menstrual disorders
A complete list
of side effects may be found in the product labeling.
11. Where can
I find more information on natalizumab and MS?
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Date created: November 23, 2004 |
