The invention pertains to improved treatment methods using DMDS, in particular cladribine, for the treatment of autoimmune diseases, in particular multiple sclerosis, and biomarkers, in particular immune cell subtypes, for predicting and/or optimising said treatment methods. The methods described rely on the use of immune cell subtypes, in particular T cells, B cells, NK cells subtypes and their ratios as present in blood samples from the patients for predicting and/or optimising the use of cladribine in the treatment of multiple sclerosis.