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 | More Details on the Suspected 4th Tysabri PML Case |
 Details are coming in slowly but surely regarding the fourth suspected case involving Tysabri and the brain infection called PML...
- Brian McGlynn, a spokesman for Elan, said it was "absolute speculation" to conclude that a fourth person had the infection. Elan and Biogen are co-developers of Tysabri
- Mr. McGlynn said the patient had NOT participated in the Tysari clinical trials-- as the other three confirmed PML patients had done. That means this patient could have received only 3 or 4 doses of Tysabri, at maximum, given the drug was introduced at the end of November 2004 and pulled just months later.
- The report made to the FDA is light on details. It lists more than 20 symptoms and conditions of the patient, including PML, without stating how the diagnoses were made. This paucity in detail seems strange given the seriousness of the matter...
- The patient had been taking Tysabri (the question of when her last dose was is not answered), Avonex, and "two other multiple sclerosis drugs" (unnamed)
- The FDA received the report on April 18th.
- Elan CEO Kelly Martin commented last week that he was very confident Tysabri would return to market
- Mr. McGlynn said that at the time, Mr. Martin "knew that there was an unconfirmed report and it continues to be unconfirmed-- Nothing has happened to make us no longer stand behind the statements he made."
Our thoughts: 20 separate symptoms and conditions, very light detail on how PML diagnosis was made (it usually requires a spinal tap and MRI), no confirmation of PML diagnosis, multiple MS therapies in combination, very few doses of Tysabri, and a unanimous 'ho-hum' from Biogen and Elan make us think this event may pan out to be a whole lot of nothing, but we will certainly await further information with baited breath.
Biogen will also hold an investor's conference call tomorrow that would almost certainly address this issue at some point.
Clicking "read more" will provide the link to the excellent New York Times article that summarizes much of this information, as well as the Biogen conference call details.
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Further Reading
4th Patient on MS drug may have brain infection (Free Registration Required)
Biogen Conference Call
Conference Call link (live at 10am EST, recorded thereafter)
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Re: More Details on the Suspected 4th Tysabri PML Case (Score: 1)
by IHaveMS-com (tim@ihavems.com) on Wednesday, June 08 @ 15:39:38 EDT
(User Info | Send a Message) | 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, such as a cancer cell (sometimes referred to as an “immortal” cell). The resulting hybrid cell, or hybridoma, 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 three cases of progressive multifocal leukoencephalopathy <http://healthlink.mcw.edu/article/921450160.html> (PML), 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 is a vaccine <http://www.pharmafrontierscorp.com/toxavin.php>, 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
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