Simplified overview of postulated mechanism of action of standard injectables and new oral therapies. Fingolimod and cladribine reduce available circulating lymphocytes by blockade of lymphocyte egress from lymph nodes (fingolimod), by cytotoxicity and depletion (cladribine). Natalizumab acts by blockade of adhesion and transmigration across the blood–brain barrier. All three drugs (fingolimod, cladribine, and natalizumab), indirectly (fingolimod and cladribine) or directly (natalizumab), reduce the number of lymphocyte in the central nervous system (CNS). In contrast, IFN-β and glatiramer acetate (GA) shift the balance of lymphocytes and modulate cytokine secretion. The newer oral therapies, terifluonamide, laquinimod, and BG-12, do not reduce lymphocytes in the CNS and appear to act in a similar way to IFN-β and GA by modulating cytokines and lymphocyte activation. None of these injectable (IFN-β and GA) and oral (terifluonamide, laquinimod, and BG-12) drugs appear to significantly reduce the numbers of circulating lymphocytes, suggesting an immunomodulatory rather than an immunosuppressive profile.