For Healthcare Professionals

Tysabri Observational Program


About the study

The primary objective of this study is to assess the long-term safety and impact on disease activity and progression of Tysabri in participants with relapsing remitting multiple sclerosis (RRMS) in a clinical practice setting.

Who can take part

You may be eligible to participate in the study if you meet the following criteria:


Key Inclusion Criteria:

  1. Documented diagnosis of Relapsing Remitting Multiple Sclerosis
  2. The decision to treat with Tysabri must precede enrollment
  3. Patient must be a new Tysabri user, and must not have had more than 3 Tysabri infusions prior to enrollment
  4. Must have had at least one relapse in the previous year, and must satisfy locally approved therapeutic indications for Tysabri


Key Exclusion Criteria:

  1. History of Progressive Multifocal Leukoencephalopathy or other opportunistic infections, or an increased risk of opportunistic infections
  2. History of positive anti-Tysabri antibodies
  3. Concomitant Immunomodulatory or immunosuppressive therapy during therapy with Tysabri
  4. Patient immunocompromised at the time of enrollment
  5. Known active malignancy
  6. Women must not be breast feeding or pregnant, or planning to become pregnant (must use birth control unless surgically sterile)

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

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Study Locations

Enter your ZIP code/Postal code/PIN code to locate study sites near you:

How to Apply

Contact the study center to learn if this study is a good match for you.

Study’s details


Relapsing-Remitting Multiple Sclerosis

Age (in years)

18 - 65

Participants needed


Est. Completion Date

Jan 3, 2029

Treatment type



Biogen identifier


Study number


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