TUESDAY, April 12 (HealthDay News) -- In a new study, close to a third of patients taking the arthritis drug Humira developed an immune system reaction to it that rendered it ineffective.
Researchers say the finding helps to explain why some people get relief from their rheumatoid arthritis symptoms while on Humira (adalimumab), which is made by Abbott Laboratories, while others gain little or no benefit. Humira belongs to a class of drugs known as biologics.
In those people for whom the drug is ineffective, the immune system realizes the drug is a foreign substance and develops antibodies to it, researchers explained. Those antibodies bind to the drug and prevent it from working.
"What the publication shows is that Humira, like many other biologic agents, may induce an immunological response against the drug," said senior study author Dr. Gerrit Jan Wolbink, a rheumatologist at Jan van Breemen Research Institute in the Netherlands. "The immunological response works against the drug. This is one of the explanations why some patients do not respond the way we hope they will."
Patients who were also taking methotrexate, another arthritis drug and an immunosuppressant, were less likely to develop the antibodies, according to the study in the April 13 issue of the Journal of the American Medical Association.
Researchers followed 272 patients taking Humira for about three years.
About 28 percent developed immune system antibodies against the drug. The reaction tended to happen within the first few months of starting treatment: About 67 percent of those who developed antibodies did so during the first 28 weeks.
Patients without antibodies had more of the drug circulating in their blood. Lower levels of the drug are a sign that the body's immune system is fighting the drug and it's being removed from the body, Jan Wolbink explained.
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