Smoking May Derail Effectiveness of MS Rx

Tysabri antibody formation associated with smoking

(RxWiki News) Natalizumab (Tysabri) can decrease the disease activity and slow the disabling effects of relapsing-remitting multiple sclerosis, but smoking may change that.

Smoking has been associated with the risk of developing antibodies to certain types of medications. It has been shown that when these antibodies form, the patient can have a reaction to the medication and the effectiveness of the medication can be reduced.

It's important to know what factors, including a patient's behavior and habits can influence a medication's effectiveness.

Recent research reported an association between smoking and the formation of antibodies to natalizumab.

"Ask your doctor for help quitting smoking."

The lead author of this study was Dr. Anna Karin Hedström from the Institute of Environmental Medicine, Karolinska Institutet, Sweden.

Natalizumab, in a class of medications called biologics, is approved to treat relapsing–remitting multiple sclerosis. It works by preventing certain immune cells from getting into the brain where they cause MS damage. Natalizumab is also used to treat Crohn's disease (a condition in which the body attacks the lining of the digestive tract, causing pain, diarrhea, weight loss and fever).

Smoking has been shown to be related to the development of antibodies to biologic medications. When this occurs, the patient may experience adverse reactions like allergies or extreme sensitivity. It is possible for antibodies to decrease the effectiveness of the medication.

Dr. Hedström and colleagues wanted to see if antibodies would be found in smokers taking natalizumab.

The researchers looked at two Swedish research studies. In these studies, 1,338 multiple sclerosis patients were treated with natalizumab. The patients had given a blood sample as part of these studies, and Dr. Hedström and team used those samples to look for antibodies to natalizumab.

Information about smoking habits was gathered, and smokers were classified as never smokers, current smokers or past smokers. The study team defined current smokers as patients who had smoked during the year when their antibody tests were run. If a patient had stopped smoking the year before the test was done, they were called a nonsmoker. The amount of cigarettes smoked and the length of time a person had been a smoker were also factors considered in the study.

Of all the patients in the study, 4.8 percent developed antibodies to natalizumab.

The research showed that the risk of smokers developing antibodies to natalizumab was 2.4 times higher than nonsmokers.

Since the definition of current smoker was set by the researchers as smokers who had smoked within the year of their antibody testing, the researchers decided to see if including people who smoked within two years of the test would change the result. The data showed that this set of current smokers had a 2.7 times higher risk of developing antibodies than nonsmokers.

The data showed a trend for a higher risk of developing antibodies with more frequent smoking, but this was not statistically significant. The research team found no association between past smoking and the development of antibodies to natalizumab.

The researchers concluded that smoking during or close to the time of natalizumab treatment was associated with developing antibodies to the medication. They recommended abstaining from smoking for multiple sclerosis patients treated with natalizumab because antibodies to the medication may decrease its effectiveness.

This study was published in December in the Multiple Sclerosis Journal.

The study was supported by grants from the Swedish Medical Research Council, the Swedish Council for Working Life and Social Research, the Knut and Alice Wallenberg Foundation, the AFA Foundation, the Swedish Brain Foundation and the Swedish Association for Persons with Neurological Disabilities.

Dr. Hedström did not disclose any conflicts of interest. The other authors declared various financial ties with several organizations and pharmaceutical companies, including Biogen Idec, the manufacturer of Tysabri.

Review Date: 
December 10, 2013