Introduction Natalizumab is licenced in the UK for highly active relapsing remitting multiple sclerosis (RRMS) which is in contrast to the original trials that only studied early RRMS. These original studies demonstrated a reduction in relapse rates of 82% after 1 year compared to the year prior to therapy. They also showed significant reductions in gadolinium-enhancing lesions and accumulating T2 lesions.

Aim To assess the effect of natalizumab on relapse rate and MRI activity in a single UK Neurosciences Centre.

Methods Three analyses were performed: clinical/MRI, nursing documentation/protocol and a patient survey.

Results Mean age was 40 years (range 19–67, n=120, 64% female) with mean disease duration of 10.3 years. Natalizumab reduced relapses by 76% compared to the year prior to therapy. 69–71% subjects were relapse-free at 1 year. When compared to baseline, gadolinium-enhancing lesions were reduced at 6 but not 12 months. Accumulating T2 lesions stabilised up to 12 months. There were wide variations in individual responses with 4% discontinuing therapy in the first year.

Discussion Clinical experience of treating highly active RRMS replicates the reduction in relapse rates seen in trials. Studying individual data may allow the identification of specific subject characteristics predicting differential responses to therapy.