Natalizumab
What evidence is there that it works?
Natalizumab is a relatively new treatment for MS and is only approved for use on the NHS for the treatment of rapidly evolving severe relapsing-remitting MS (RES). This was discussed in more detail in the earlier section 'What are disease modifying drugs?'.
The main study looking at the effectiveness of natalizumab in MS was the AFFIRM study (Polman 2006) which was a phase III randomised, double blind placebo controlled trial - where some people were treated with natalizumab, and some with a dummy drug, and then the results were compared between the two groups. Not everyone in the study had RES.
The AFFIRM study showed that natalizumab reduced the rate of relapses by 68% and this was maintained at two years into treatment. In other words, on average it cuts relapses by about two thirds. It also showed that natalizumab reduced the risk of sustained disability progression by about 50% over two years.
In the patients with rapidly evolving severe relapsing-remitting MS (RES), the results were better still. Natalizumab reduced the rate of relapses by 81% and reduced the risk of sustained disability progression by 64% over two years.
There have been no studies directly comparing natalizumab with interferon beta or glatiramer acetate. One study (the SENTINEL study - Ruddick 2006) compared natalizumab taken together with interferon beta against interferon beta alone. However, natalizumab is not licensed to be taken jointly with interferon beta because of the risk of serious side effects.
However, comparing data from the AFFIRM study with existing studies of interferon beta and glatiramer acetate shows that for patients with RES, natalizumab is significantly more effective at reducing relapses. The data suggests that patients treated with natalizumab experience only about half as many relapses as those treated with the interferon beta or glatiramer acetate.
