(BBC News) A drug that alters the immune system has been described as "big news" and a "landmark" in treating multiple sclerosis, doctors and charities say.
Trials, published in the New England Journal of Medicine, suggest the drug can slow damage to the brain in two forms of MS.
Ocrelizumab is the first drug shown to work in the primary progressive form of the disease.
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The drug is being reviewed for use in the US and Europe.
MS is caused by a rogue immune system mistaking part of the brain for a hostile invader and attacking it.