[Oral cladribine for relapsing-remitting multiple sclerosis: another purine analogue or a genuine therapeutic innovation?].

Azathioprine (AZA) is a purine analogue which has been used in the treatment of multiple sclerosis (MS) for over 30 years. After the approval of immunomodulatory drugs, such as recombinant interferon beta and glatiramer acetate, AZA now only plays a minor role in MS therapy. The results of a recently published phase III trial (CLARITY trial) involving an oral formulation of the purine analogue cladribine, a substance which is at least structurally related to AZA, may soon lead to the approval of cladribine tablets as a new oral MS therapeutic. The following overview provides a comparison of the mode of action, side-effect profile and data currently available on AZA and cladribine in the treatment of MS.