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.  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. It destroys the protective coating that wraps round nerves called the myelin sheath. The sheath also acts like wire insulation to help electrical signals travel down the nerve. 

    Damage to the sheath prevents nerves from working correctly and means messages struggle to get from the brain to the body. This leads to symptoms like having difficulty walking, fatigue and blurred vision. Ocrelizumab kills a part of the immune system - called B cells - which are involved in the assault on the myelin sheath. 

    In 732 patients with progressive MS, the percentage of patients that had deteriorated fell from 39% without treatment to 33% with ocrelizumab. Patients taking the drug also scored better on the time needed to walk 25 feet and had less brain loss detected on scans. 

    In 1,656 patients with relapsing remitting, the relapse rate with ocrelizumab was half that of using another drug. Prof Gavin Giovannoni, from Barts and The London School of Medicine and Dentistry, was involved in the trials and said: "The results shown by these studies have the potential to change how we approach treating both relapsing and primary progressive MS". 

    He told the BBC: "It's very significant because this is the first time a phase three trial has been positive in primary progressive MS". More than 100,000 people are diagnosed with MS in the UK, around one-in-five are progressive.

Source: QNA