Multiple Sclerosis Society of Canada



  • Brand name: Tysabri (Biogen Canada Inc.)
  • Route of Administration: Intravenous infusion
  • Approved for treatment in RRMS. Clinical phase II and phase III trials investigating the safety and efficacy of its treatment for primary and secondary progressive MS are underway. Results of the phase III trial in people living with secondary progressive MS are summarized below.

Research and Results:

A phase III study (ASCEND) was undertaken to investigate whether natalizumab can slow accumulation of disability unrelated to relapses in people living with secondary progressive MS. The randomized, double-blind, placebo-controlled trial involved 889 participants in sites spanning 15 countries. Participants received either 300 mg natalizumab intravenously every four weeks for 96 weeks, or placebo on the same schedule. The study used three disability measurements as part of its composite primary endpoint to evaluate the efficacy of the drug in reducing disability progression.

Recently released results from the trial demonstrated that natalizumab failed to reach its primary endpoint of reducing confirmed disability progression, leading Biogen not to pursue secondary progressive MS as an indication for natalizumab at this time. Natalizumab was well tolerated by participants, and additional endpoints confirmed what is known about its efficacy in reducing relapses and new brain lesions.

Click here for information on Natalizumab as a treatment for RRMS.