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.

Tysabri received FDA approval in 2004 on the basis of the Phase III AFFIRM trial, in which the medication reduced the risk of progression of disability by 42 to 54 percent, and reduced the annual rate of relapse by two-thirds. Tysabri was voluntarily withdrawn from the market the next year, however, after three cases of progressive multifocal leukoencephalopathy (PML), a rare but potentially fatal brain infection caused by the JC virus, were identified in people taking the medication. Tysabri became available again in 2006, based on the implementation of a comprehensive risk-management program, which includes testing potential Tysabri users to see if they have anti-JC virus antibodies.14

Now it appears that extending the dosing of Tysabri from every four weeks to every 12 weeks can significantly reduce the risk of developing PML. Research presented in February 2018 at the Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2018, drew on six years of safety data and found that using an extended dosing regimen could reduce the risk of PML by up to 94 percent.15

A French study presented at the ECTRIMS-ACTRIMS Meeting in October 2017 gave further support to extended-interval dosing by reporting that administering Tysabri every five or six weeks, rather than every four weeks, did not diminish the efficacy of the agent. The study followed 70 individuals who moved to extended-interval dosing after receiving Tysabri every four weeks for two years. After 18 to 20 months on the longer dosing intervals, no significant differences were found between four-week dosing and five- or six-week dosing in terms of the patients’ annualized relapse rates, EDSS scores, number of T2 lesions seen on MRI, or a measure of how well the drug is reaching target cells.16

The identification of strategies for reducing the risk of PML is particularly welcome given that other recent research has further demonstrated the effectiveness of Tysabri in treating RRMS.

The impact of Tysabri on cognitive function, health-related quality of life (HRQoL), and work capacity in people with early RRMS was examined in the Observational Study of Tysabri in Early Relapsing-Remitting Multiple Sclerosis in Anti-JC Virus Antibody Negative Participants (STRIVE). This open-label, single-arm, multi-center study followed 222 individuals over the course of two years of treatment with Tysabri. At baseline, the patients had been diagnosed with MS an average of 1.6 years earlier. Half of the participants had not received another disease-modifying therapy (DMT) before starting Tysabri.17

The study results were presented at the ECTRIMS-ACTRIMS Meeting in October 2017. Researchers found that after two years of Tysabri therapy, patients had significant improvement in cognitive function and HRQoL based on change from baseline on standardized test scores. These individuals also showed improvement in work capacity as measured by hours missed from work due to MS and non-MS reasons, work productivity affected by MS, and daily activities affected by MS.17

Meanwhile, data from the 10-year Tysabri Observational Program (TOP) involving almost 2,500 patients found that people who switched to another therapy after two years on Tysabri had more than double the risk of relapse compared to individuals who remained on Tysabri.18

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