A new study recently reported in the Journal of the American Medical Association suggests that the interferon beta drugs widely used in treating relapsing-remitting MS may have little or no effect on a person’s progression to disability.
However, the study’s senior author, Helen Tremlett, an associate professor of neurology at the University of British Columbia, cautioned that the study does not show that interferon beta is useless.
“These drugs were licensed because they reduce relapse and have a better outcome with lesions,” she says. “That has not changed.”
Interferon beta drugs currently on the market include Betaseron®, Avonex®, Rebif®, and Extavia®.
Researchers at the University of British Columbia prospectively collected data on 868 people with MS treated with interferon beta, comparing them with 1,788 people who never took the drug. Using a well-validated scale, they found that those who took interferon beta were no less likely to suffer long-term disability than those who took none.
Previous studies have found that interferon beta does prevent disability, but the authors point out that many of them were marred by methodological problems — the use of control groups too ill to start medication, for example — that this study avoided.
At the same time, they acknowledge certain weaknesses of their own study, in particular the problem that people who take no medicine are also likely to be among those who are the least ill and therefore least likely to become disabled in any case.
But after controlling for sex, age at onset, disease duration, relapse rate and other factors, they could find no association between taking interferon beta and any reduction in progression to disability. Relapses and brain lesions do not, apparently, drive disability, Dr. Tremlett said.
“There may be other processes at work,” she added. “In an ideal world, we want drugs that target whatever is driving long-term disability. We need other drugs aiming at other targets in the brain.”
MSF Senior Medical Advisor Ben Thrower, M.D., notes that in addition to contradicting earlier studies, “This study also seems to contradict what we see in real life. Most healthcare providers who work with MS would argue that beta interferons seem to have a slowing effect on disability progression in the clinic.”
Another factor to consider, according to Dr. Thrower, is whether disability is being measured appropriately. “Most studies still use the EDSS to measure disability. This is a relatively crude measure that is very heavily weighted towards measuring walking ability. Cognitive dysfunction and fatigue are the two most vocationally-limiting symptoms seen with MS and are not measured well by the EDSS,” he says.
Additionally, he says, the statement that relapses and MRI brain lesions have no effect on disability is controversial. While it is true that disability can worsen in progressive forms of MS without relapses or new MRI lesions, other studies have shown an association between new lesions on MRI and/or relapses and the risk of disability.
”The bottom line is that while this study is a little discouraging, it should not mean that we give up on a whole class of drugs for helping manage MS, “Dr. Thrower says.
The study was supported by grants from the Canadian Institutes of Health Research and the National Multiple Sclerosis Society. The British Columbia Multiple Sclerosis database has been funded from those sources and also by an unrestricted grant from Donald Paty, MD, of theUniversityofBritish Columbia, and the MS/MRI Research Group.