Neutralizing antibodies - and what they mean.
One third lose the benefit
But after a year and a half, the balance of the group -- 38%, or slightly more than a third -- were having just as many relapses as people taking an inert placebo injection. They had lost the benefit of a reduced relapse rate. In addition, their MRIs revealed increased areas of MS damage (lesions).
The culprit appears to involve neutralizing antibodies, which this portion of the group had developed in response to the presence of Betaseron, a foreign protein, in their systems.
Study group findings
The Interferon Beta MS Study Group and the British Columbia MS/MRI Analysis Group published an analysis of 3 years' experience with patients doing poorly on Betascron in the October 1996 issue of Neurology. The analysis confirmed that treatment benefits were reduced in about one third of those treated after 18 months. The appearance of neutralizing antibodies is associated with this change. The analysis also revealed:
* There were no differences in people or their MS that predicted who would develop antibodies and who would not. For example, there was no connection to having a more rapidly progressive MS and developing antibodies.
* Some people who tested positive for the antibodies and continued to take Betaseron went back to being antibody-negative later on.
* While some people lost their neutralizing antibodies, and a few others developed them after more than 18 months, most people who were negative after two years never developed antibodies at all. The overall proportion of antibody-positive people never exceeded 38%. It appears that continued use of the drug will not inevitably cause everyone to develop the antibodies.
* There is no evidence that anyone is harmed by these neutralizing antibodies -- but their long-term impact is not yet known.
Who should be tested?
The guidelines published in Neurology recommend that people who are doing well on Betaseron do not need to be tested at all. If testing is called for, the standard tests such as ELISA or Western Blot will not work. Berlex Laboratories has developed a test called the MxA assay which has not been validated and is under study. Physicians may use it free of charge as part of an on-going investigation.
Antibodies to Avonex
About 20% of people taking Avonex also develop neutralizing antibodies but they do not appear to be linked to a loss of treatment benefit. Until larger numbers of people taking Avonex are followed for longer periods of time, most questions about neutralizing antibodies and Avonex can't be answered. For example, it is not known if having antibodies to Betaseron can influence a person's response to Avonex or if a person's antibodies to Betaseron decrease or disappear if they switch to Avonex.
In discussing treatment options, Dr. Whitaker commented: "We are simply not at a point where we can use antibody status for guidance about drug choices. We have to base our choices on how an individual is doing."
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|Title Annotation:||in multiple sclerosis care|
|Date:||Mar 22, 1997|
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