This page will give you an overview of the benefits and risks of Tysabri and allow you to calculate your risk
Tysabri (Natalizumab) is a drug that has shown a reduction in relapses for Multiple Sclerosis.
Detailed information about the drug can be found on the European Medicines Agency: Tysabri product information datasheet.
The benefits of Tysabri depend on how active your MS is.
If you’ve had at least 1 relapse in the last 12 months:
68%
reduction in relapse rates
42%
reduction in disability progression
5x
more likely to be free of disease activity*
If you’ve had at least 2 relapses in the last 12 months AND at least 1 active, or enhancing, lesion on MRI:
81%
reduction in relapse rates
64%
reduction in disability progression
16x
more likely to be free of disease activity*
*Free from disease activity means relapse free, no progression and no new lesions on MRI
As with most drugs, there are risks linked to the long term use of Tysabri. The main risk is a potentially fatal brain infection, called progressive multifocal leukoencephalopathy (PML).
PML is caused by the JC virus, a common virus completely unrelated to MS. The virus has no symptoms so we don't know we've got it. You must have been infected with the JC virus to be at risk of PML
Almost half of the general UK population are infected with JC virus in childhood and adolescence. It is unknown how you catch the virus, but you excrete it in your urine and we think it is found in the tonsils. A JC virus test will detect if you have anti-JC antibodies, meaning you have been infected with the virus at some point.
We need our white blood cells to fight off infections. Tysabri can suppress the immune system and blocks white blood cells from getting into the brain. That means if we get an infection (like PML) that attacks the brain, our immune system can't fight it.
It's impossible to predict if you'll get PML, but there are a number of factors that can increase your risk.
You must have the JC virus.
Your risk increases if you have previously taken an immunosuppressant. These are drugs that reduce the activity of your bodies immune system.
Your risk increases the longer you have been on Tysabri, especially over 2 years.
Your risk increases with a higher titre level. This is the level of antibodies in your blood.
Find your estimated risk of developing PML by answering the questions below:
Have you previously taken an immunosuppressant?
Do you know your titre level?
(If not, we'll use an average)
What is your titre level?
How many months have you been on Tysabri:
Your estimated risk is:
1 in
JCV Positive and taken an immunosuppressant
JCV Positive
JCV Negative
The numbers of MS patients developing PML are now falling due to careful monitoring by their clinical team.
If you are currently JC virus negative, you will be retested every 6 months to see if you are still negative.
If you become JC virus positive and are uncomfortable with the increased risk, there are alternative treatment options available. These should be discussed with your clinical team
Your clinical team can monitor your titre levels and you can be removed from the drug when the risks become too high
If you are identified as being at higher risk, your clinician may do regular 3 monthly MRI scans to identify PML at a very early stage.
JCV positive patients receiving Tysabri every 5-6 weeks, rather than every 4 weeks, reduces the risk of PML by more than:
88%
The severity depends on when PML is detected. If it’s detected before it causes physical symptoms the effects are less severe.
PML can be detected early, before it causes symptoms, with regular 3-4 monthly MRI scans.
With early detection there is low risk of
physical disability with a
1 in 30
chance of death
Late detection is when PML is allowed to develop and presents with neurological symptoms.
With late detection there is high risk of
physical disability with a
1 in 3
chance of death
The symptoms of PML depend on where the infection is in the brain but the most common are personality changes, cognitive problems, similar symptoms to a MS relapse and epileptic attacks.
The most effective treatment of PML is to get Tysabri out of the body and let the immune system back in the brain to identify the infection and clear it. This means stopping the drug and washing it out using a treatment called plasma exchange.
You may be able to transfer to another treatment.
This page was compiled from a range of sources: