* antibody that makes it difficult for immune system cells to

       move into the brain and spinal cord

    * for relapsing remitting MS that has not responded

       to other treatment

    * reduces relapse rate

    * IV infusion once every four weeks

    * 1/3 of patients improve in disability, suppresses 90% of MRI disease

    * increases risk (1:1000) of viral infection of the brain

    * infrequent side effects: headache, pain, fatigue, diarrhea, depression

    * approved in 2006