Multiple Sclerosis Treatment: Neutralizing Antibodies
Some — but not all — multiple sclerosis (MS) patients who take one of the interferon beta medications (Avonex, Betaseron, Extavia, or Rebif) develop a form of antibody known as a neutralizing antibody (NAb), so called because it interferes with the biological activities of the interferon. When they occur, NAbs typically develop 12 to 18 months after the start of treatment.
Even though NAbs seem to have an impact on relapse rates, the development of new lesions in the CNS, and perhaps on disease progression, neurologists are still learning how best to use this information in treating their patients. Here are the factors that doctors must take into consideration:
The higher-dose, more frequently administered interferons (Betaseron, Extavia, and Rebif), which have been shown to produce more NAbs than the lower-dose interferon (Avonex), may also provide greater short-term benefit than the lower-dose interferon.
NAbs can disappear after a period of time. In other words, a person who tests antibody-positive after several months on an interferon medication may then become antibody-negative some time later.
Some people seem to do well on their interferon medication in spite of developing NAbs, while others do poorly on an interferon medication even without developing NAbs.
For these reasons, most MS specialist neurologists believe that treatment decisions are best made by evaluating how a person is feeling and functioning rather than by measuring NAbs. If a person’s MS remains very active in spite of being on an interferon medication and he or she tests positive for NAbs on more than one occasion, the doctor may recommend that the person switch to a non-interferon medication.