Tysabri® (natalizumab)

FDA-Approved Medications: New Data

Company: Biogen

  • 300 mg given via IV infusion every four weeks
  • Approved in 2004 for RMS

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This laboratory-produced monoclonal antibody acts against a molecule involved in the activation and function of lymphocytes (immune-system cells produced to fight infection and disease) and their passage into the central nervous system (CNS). The CNS consists of the brain, spinal cord, and optic nerves.

A small Phase II clinical trial, Natalizumab Treatment of Progressive Multiple Sclerosis (NAPMS), was performed at Copenhagen University Hospital to study the safety and efficacy of Tysabri treatment of primary-progressive MS (PPMS) and secondary-progressive MS (SPMS).8 It enrolled 24 patients and showed a reduction in markers of inflammation in the spinal fluid, as well as evidence of protection of brain tissue on modern MRI measures. This proof-of-concept study provided encouraging evidence that Tysabri may have beneficial effects in progressive forms of MS.

To continue this line of investigation, a large, randomized trial of Tysabri in SPMS called ASCEND9 evaluated the effects on the accumulation of disability in people with SPMS. There were 889 SPMS patients enrolled, the majority of whom required assistance for walking and were no longer experiencing MS relapses. Subjects were randomized to receive either Tysabri 300 mg or placebo intravenously every four weeks for 96 weeks.

The results of the ASCEND study were officially presented at the 2016 AAN meeting in Vancouver, British Columbia. The main question under study was whether SPMS patients on Tysabri had decreased overall disability progression during the trial versus those on placebo. The study investigators found that there was no statistical difference in the number of patients with disability progression on Tysabri (44 percent) versus those on placebo (47 percent) and thus the study did not meet its primary aim. There was, however, less progression seen in Tysabri patients in terms of worsening of upper arm function. Also, as would be expected, fewer relapses and new MRI lesions were seen in the Tysabri group. In summary, Tysabri does not seem to be effective in preventing overall disability progression in SPMS, although it may have some benefit in those who continue to have relapses or new MRI disease activity.

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