What is Tysabri?

Tysabri is a new drug for people with relapsing remitting MS. It works in a different way to the current disease modifying treatments (beta interferons and glatiramer acetate) by preventing immune cells leaving the blood stream and entering areas the brain and spinal cord where they can cause inflammation and damage.  

Is Tysabri available now?

Tysabri is licensed for use in the UK and has been approved for treatment on the NHS for people with rapidly evolving, severe, relapsing remitting multiple sclerosis (defined by two or more disabling relapses a year and evidence of new lesions on MRI brain scans).

Tysabri is not available in combination with beta interferon and people who have a history of immunosuppressive therapies may not be suitable for treatment with Tysabri.
 

History

Based on phase III clinical trials in the US, Tysabri (Natalizumab) was approved in 2004 for the treatment of relapsing remitting MS. It was subsequently withdrawn from the market by its manufacturer after it was linked with three cases of the rare neurological condition progressive multifocal leukoencephalopathy (PML) when administered in combination with beta interferon.

Whether the risk of developing PML is enhanced by the combination of other immune suppressive drugs, or whether the risk is increased after longer term treatment with Tysabri is unknown. Based on data from the phase III clinical trials the risk of developing PML was estimated to be around 1:1000. The products labelling and patient information reflect this risk.

After a review of safety information and no further deaths, the drug was returned to the US and EU market in 2006 under a special prescription program. It was no longer made available in combination with beta interferon. As part of the risk-minimisation programme, all people taking Tysabri are registered and monitored.

Due to the risk of PML only people with severe evolving forms of relapsing remitting MS are eligible for treatment.  

How effective is Tysabri in reducing relapse rate or slowing disease progression?

At the end of a two-year study, Tysabri reduced how often relapses occurred by 67 per cent compared with placebo.

In other words, 72 per cent of people taking Tysabri had no relapses at the end of the two-year study compared with 46 per cent of people taking the placebo.

At the end of a two-year study, Tysabri slowed the worsening of disability that is common in people with MS. Tysabri reduced the chance a person’s disability would worsen by 42 per cent compared with placebo.

In other words, 17 per cent of people taking Tysabri had their condition worsen, while 29 per cent of people taking a placebo had their condition worsen.
 

How is Tysabri taken?

Tysabri is given once a month as an intravenous infusion (a drip) over a one-hour period in a hospital or clinic setting. Observation for an hour is required following the infusion.  

Side Effects

In clinical trials, two cases (including one fatality) of PML occurred in people with MS who were being treated with Tysabri as well as beta interferon. In another trial using Tysabri to treat Crohn’s disease, one person who had a history of being treated with immunosuppressants also developed PML and died.

Each of the cases of PML in the clinical trials occurred in people using both Tysabri along with other immunosuppressant or immune modulating drugs. People are no longer able to take Tysabri along with other immunosuppressant or immune modulating drugs.

Two new cases of PML have been confirmed

In terms of other side effects, Tysabri can be associated with infections, headaches, dizziness, vomiting, nausea, liver damage and infusion reactions.

Many of the more significant side effects that have been associated with Tysabri are treatable and anyone taking a disease modifying drug should be monitored for any problems. As with all treatments, the benefits must be weighed with the risks of side effects and discussed between you and your doctor.