Current state of knowledge of the topic of the project and The general interest of the project; Pharmacogenomic aims to determine biomarkers related to treatment response, a step toward patient-tailored medicine. Natalizumab, a monoclonal antibody has just received the EMEA approval for MS patients who do not respond to interferon treatment or who experience a severe disease course. Efficacy of the drug is outstanding with 37% of the patients completing the "disease free" definition after 2 years (7% in placebo group). On the other hand, natalizumab may be associated with severe adverse events such as progressive multifocal leucoencephalopathy and high costs. Overall, this emphasizes the need beyond current approval criteria to identify those patients with the best efficacy to safety ratio, a major public health issue.