Multiple Sclerosis (MS) is an immune-mediated inflammatory disease affecting the central nervous system (the brain and spinal cord). The symptoms are caused by an immune response attacking and damaging the myelin sheaths surrounding and insulating nerve fibers. This causes inflammation and impaired nerve communication within the central nervous system causing the patient to suffer relapses and physical and mental disease progression. The etiology of the disease is unknown, but is assumed to depend, like other autoimmune diseases, on both genetic and environmental factors.
There are various forms of MS, the most common is relapsing remitting MS (RRMS). It is characterized by unexpected recurring relapses that can last from a few days to a few weeks and are followed by complete or partial remission. In approximately 80 percent of all patients, the disease begins as RRMS but most develop after some ten or so years into secondary progressive MS (SPMS), which is characterized by a gradually increasing degree of disability, without the recovery periods. The disease can also be primary progressive (PPMS), i.e. without any periods of relapses and remissions. PPMS is a less common form of MS affecting 10-15% of patients diagnosed with MS.
MS primarily affects young and middle-aged people. The disease often first appears when the patient is between 20 and 50 years old, and the number of women affected is twice as high as the number of men. A total of about two million people throughout the world suffer from MS. The disease is more common in the northern hemisphere. The Nordic region, the British Isles and North America are regarded as high-risk areas.
There are currently several types of disease modifying drugs available for treatment of MS. Since many years the injectable beta-interferon products and glatiramer acetate have been available and are still widely used. More recently, three injectable antibody products, natalizumab, alemtuzumab and daclizumab have been approved for treatment of MS. There are also four oral products approved during the last few years, fingolimod, teriflunomide, dimethyl fumarate and cladribine (not yet approved in US). The drugs reduce the number of relapses and are therefore all approved for treatment of MS patients with relapses. In 2017 the first product for treatment of both relapsing MS and PPMS, the injectable ocrelizumab, was approved in the US. The majority of available oral and more recently approved injectables are also immunosuppressive which may lead to adverse effects such as opportunistic infections or carcinogenicity by long term treatment in chronic diseases such as MS. Thus, there is still need for non-immunosuppressing drugs such as laquinimod in the tool box for neurologists treating patients with MS.