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A to Z of MS Neutralising antibodies

Antibodies are created by the immune system as part of the response to foreign objects, such as bacteria and viruses. Antibodies are proteins that lock onto the surface of the invading particle helping the body to kill it off.

It is known that some people develop antibodies to the beta interferon drugs (Avonex, Betaferon and Rebif) and natalizumab (Tysabri). These are known as neutralising antibodies as they can reduce the effectiveness of these drugs. Over the long-term, this may mean that people taking the beta interferons or natalizumab receive less benefit from them and experience a similar number of relapses as they would have done before taking the drugs.

About 30% of people on Betaferon, 25% on Rebif, and 5% on Avonex will develop neutralising antibodies. In some people the neutralising antibodies will disappear again over time. Around 6% of people taking Tysabri develop persistent neutralising antibodies, which are usually evident from around three months of treatment.

A recent review by the European Forum of Neurological Sciences has recommended that people receiving the beta interferon drugs should be tested for neutralising antibodies at 12 months and two years after starting treatment. If neutralising antibodies continue to be present at two years, are present in high levels, and an individual is beginning to experience more MS-related symptoms, then there is a case for stopping or switching treatment. However, the presence of neutralising antibodies alone is not a reason to stop or to change drugs unless there is other evidence that the treatment is not working. The neurologist will make a decision which should be in partnership with the individual.

There are as yet no clinical guidelines about testing for neutralising antibodies with Tysabri, and this will depend on the neurologist's discretion.

Although they can limit the effectiveness of drugs, neutralising antibodies are not associated with any new side-effects or long-term safety issues.

Antibodies have been shown to develop in some people who take glatiramer acetate (Copaxone), although one study suggests that this had no effect on the effectiveness of the drug.

Anyone who develops neutralising antibodies may be eligible to switch to another treatment, eg to glatiramer acetate from beta interferon, or to mitoxantrone following treatment with natalizumab. However, this will depend on individual experience and the neurologist's discretion.

References

Calabresi PA, et al.
The incidence and significance of anti-natalizumab antibodies: results from AFFIRM and SENTINEL.
Neurology 2007;69(14):1391-1403.

Sorensen PS, et al.
Guidelines on use of anti-IFN-beta antibody measurements in multiple sclerosis: report of an EFNS taskforce on IFN-beta antibodies in multiple sclerosis.
European Journal of Neurology 2005;12(11):817-827.

Teitelbaum D, et al.
Antibodies to glatiramer acetate do not interfere with its biological functions and therapeutic efficacy.
Multiple Sclerosis 2003;9(6):592-599.

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