Medications are modestly effective at decreasing the number of attacks in RRMS and in reducing the accumulation of brain lesions, which is measured using gadolinium - enhanced magnetic resonance imaging (MRI).  Interferons and glatiramer acetate are roughly equivalent, reducing relapses by approximately 30% and their safe profile make them the first-line treatments.  Nevertheless, not all the patients are responsive to these therapies. It is known that 30% of MS patients are non-responsive to Beta interferon.  One of the factors related to non-respondance is the presence of high levels of interferon beta neutralizing antibodies . Interferon therapy, and specially interferon beta-1b, induces the production of neutralizing antibodies, usually in the second 6 months of treatment, in 5 to 30% of treated patients.   Moreover, a subset of RRMS patients with specially active MS, sometimes called "rapidly worsening MS" are normally non-responders to immunomodulators and are treated with either mitoxantrone or natalizumab.