Multiple sclerosis treatment faces tremendous changes owing to the approval of 
new medications, some of which are available as oral formulations. Until now, 
the four orally available medications, fingolimod, dimethylfumarate (BG-12), 
teriflunomide, and cladribine have received market authorization, whereas 
laquinimod is still under development. Fingolimod is a sphingosine-1-phosphate 
inhibitor, which is typically used as escalation therapy and leads to up to 60% 
reduction of the annualized relapse rate, but might also have neuroprotective 
properties. In addition, there are three more specific S1P agonists in late 
stages of development: siponimod, ponesimod, and ozanimod. Dimethylfumarate has 
immunomodulatory and cytoprotective functions and is used as baseline therapy. 
Teriflunomide, the active metabolite of the rheumatoid arthritis medication 
leflunomide, targets the dihydroorotate dehydrogenase, thus inhibiting the 
proliferation of lymphocytes by depletion of pyrimidines. Here we will review 
the mechanisms of action, clinical trial data, as well as data about safety and 
tolerability of the compounds.