This chapter presents the literature review on disease-modifying therapies (DMT) for children with multiple sclerosis (MS). Four first-line DMTs have been approved for treatment of relapsing-remitting (RR) MS in the adult population. They include glatiramer acetate, interferon beta (IFNB)-1a IM, IFNB-1a SC, and IFNB-1b SC. Large phase III studies showed that chronic administration of recombinant IFNB reduced the number of relapses and slowed progression of physical disability in adult patients with RR MS. Abnormalities in liver function tests (LFTs) may be pronounced in younger children taking interferon. The glatiramer acetate is designed to mimic human myelin basic protein and is postulated to induce the myelin-specific response of suppressor T-lymphocytes and to inhibit specific effector T-lymphocytes. Breakthrough disease is a concern in the pediatric MS population. Proposed consensus criteria for breakthrough disease in adults include increase in relapse number, new or recurrent MRI lesions, and worsening of cognitive or motor disability.

In adult breakthrough disease, treatment strategies include switching to another first-line agent, adding another agent to the on-going therapy, or switching to a second-line drug such as natalizumab or immunosuppression. Therapeutic strategies such as switch to a second-line agent are typically associated with the possibility of more severe adverse events than those seen with first-line agents, including life-threatening conditions such as progressive multifocal leukoencephalopathy (PML), leukemia, secondary cancers, or infections. The primary goal of breakthrough therapy in pediatric multiple sclerosis (MS) is to prevent disease activity and disability progression in patients who have continued disease activity despite appropriate first-line therapy. Methotrexate (MTX) is a dicarboxylic acid used in the treatment of various cancers and autoimmune diseases. Combination therapy of either first-line drugs or first-line drugs with a second-line agent is sometimes used as an approach to obtain better disease control in breakthrough MS.