Re: What's the skinny on Tysabri?
- From: "Tim" <twesner@xxxxxxx>
- Date: 24 Jul 2005 10:13:07 -0700
I was asked to write a comparison of Tysabri and Tovaxin, here it is.
Tysabri was approved last November for use with people suffering from
MS. It reduces the number of attacks by 2/3 verses 1/3 with the current
drugs. It reduces brain liaisons by 90% and reduces the progression of
disability by 44%. It got fast tracked and was heralded as the next
generation of MS treatments. It was the drug that Tovaxin would have
gone head-to-head with in Phase III clinical trials.
What is Tysabri? It is a Monoclonal Antibody
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Monoclonals.html
-- an antibody that is mass-produced in the laboratory from a single
clone and that recognizes only one antigen. Monoclonal antibodies are
typically made by fusing a normally short-lived, antibody-producing B
cell to a fast-growing cell. The resulting hybrid cell multiplies
rapidly; creating a clone that produces large quantities of the
antibody.
MS is considered to be an autoimmune disease in which the person's
immune system attacks the brain and/or spinal cord. Tysabri appears to
work by binding to these immune system cells, thus preventing them from
traveling to the brain where they can cause damage.
Antibodies are proteins produced by a person's immune system to fight
foreign substances, such as infections. Monoclonal antibodies, such as
natalizumab (Tysabri), can be produced in large quantities in cell
culture in a laboratory setting. They can be designed to bind to
proteins on the body's normal cells. By recognizing and attaching to
these proteins, 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 such as
MS.
What killed the patient? The reports involved at least three cases of
progressive multifocal leukoencephalopathy (PML)
http://healthlink.mcw.edu/article/921450160.html , a rare but often
fatal disease that affects the nervous system. In two of the cases, the
patients had been taking Tysabri for more than two years in combination
with another MS drug, Avonex. In the third case, the person was taking
only Tysabri and was in a Crohn's Disease study.
It is suspected that Tysabri or the combination of Tysabri and Avonex
allowed this rare viral infection to take hold. 80% of all adults have
been exposed to this virus, but it is rare for someone to be affected
by it. Someone with a compromised immune system, such as AIDS, would be
a candidate to get this. Possibly Tysabri or the combination of the two
drugs altered the patients immune system enough to allow the virus to
attack.
PML is a demyelinating disease and it was first thought that these
patients were having an MS attack. There is no known cure for PML and
diagnosis is usually done by autopsy. It may be possible to diagnose it
with a spinal tap, but currently, an MRI assessment is used when PML is
suspected.
What does Tysabri's withdrawal mean to the approval of Tovaxin, and
whether or not Tovaxin will get fast tracked? Tysabri has no bearing on
whether or not Tovaxin gets approved. Tysabri is a monoclonal antibody
and Tovaxin is an autologous T-cell elimination. Tysabri is a
laboratory created antibody that attaches itself to T-cells thus
preventing them from crossing the blood-brain barrier. It stops almost
all T-cell from crossing, not just the bad ones.
Tovaxin http://www.pharmafrontierscorp.com/toxavin.php is a vaccine,
which uses the patient's own blood. Like a flu shot, it makes the body
form antibodies against a select T-cell, which attacks myelin. It does
not interfere with any other T-cells and has no effect on the
blood-brain barrier. There is virtually no health risk. The typical
frequency of myelin reactive T-cells in the blood of a patient with MS
is about 1 to 2 per million. Eliminating this small fraction of T-cells
from a person's immune system has very little effect.
Since Tovaxin is autologous and posses little health risk, if a small
portion of patients show improvement (10%), it will get fast tracked.
The current drug escalation trials have show that it is safe and almost
all of the patients have shown improvement.
----------------------------
Hi to all,
I am in an FDA trial for an MS vaccine. The vaccine appears to have
arrested my disease and has done the same for the other people in the
study. I have two small websites that show a timeline of events. The
first one is www.ihavems.com It starts with the first injection and
goes for 18 months. My websites are little 10-page boilerplate sites,
so my timeline continues on a second website www.timswellness.com from
June 2004 to the present. I am a little behind on the second website. I
haven't written anything since the end of February, but I will get back
to it soon. My Dad and I work on it together.
I am actually out doing things again. I just returned from a solo trip
to see some friends in San Francisco. This is amazing, since two years
ago, my parents were taking me from our home in Michigan to Houston in
a wheelchair.
Tovaxin is an autologous vaccine. That means they take some of my
blood, cull out the T-cells and introduce them to human myelin. Those
that react to the myelin are culled out and replicated. Once there are
enough for the vaccine, about 45 million cells, the T-cells are
irradiated so that they are still alive, but cannot reproduce. That is
the vaccine.
The vaccine is injected just under my skin, you can see some pictures
at www.timswellness.com , and the body treats these T-cells as a
foreign invader and makes antibodies to eliminate only these specific
T-cells. These antibodies not only take out the T-cells from the
vaccine, but also eliminate all of that same type of T-cell throughout
my body.
The body produces 2 to 3 trillion red blood cells per day. I am not
sure how many T-cells are produced per day, but if 1 or 2 per million
are troublemakers, that means there are hundreds of millions of myelin
reactive T-cells floating around in the blood stream of someone with
MS. A flare is when the body produces too many of these bad T-cells. No
one is sure why this happens, but it may be caused by an upper
respiratory infection, or a cold sore, or some other immune response
that triggers the body to produce T-cells that mistake myelin as
something bad.
By eliminating these 1 or 2 per 1 million T-cells does not compromise
the immune system, but it does eliminate all of the T-cells that
destroy the myelin. No bad T-cells means no more attacks. Anyone on
Tovaxin will need to get a booster twice a year to keep the antibodies
at a level sufficient to continue to eliminate all of the myelin
reactive T-cells as they are produced. This is just like a flu shot.
I think about 30 to 40% of the damage that was done by the attacks has
been reversed. The body will repair itself, as long as the attacks
stop. I am helping myself by doing a lot of exercising and activities
that improve my small motor skills.
I am doing many things that I was no longer able to do. When I started
the vaccine, my parent's were cutting my food and feeding it to me. I
am able to cut my own food, and today, I peeled some shrimp. Realizing
that I can again do something as insignificant as peel a shrimp really
makes me feel good. I used to wonder why people got so excited to see a
disabled family member regain some little ability, now I understand,
and I understand why my family is trilled at even my smallest
improvement.
Best regards, Tim
.
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