Exploratory Study of the Safety, Tolerability and Efficacy of Multiple Regimens of Natalizumab in Adult Participants With Relapsing Multiple Sclerosis (MS)
Exploratory Study of the Safety, Tolerability and Efficacy of Multiple Regimens of Natalizumab in Adult Participants With Relapsing Multiple Sclerosis (MS)
The primary objective of this study is to explore the effects of multiple regimens of
 natalizumab on disease activity and safety in participants with relapsing-remitting Multiple
 Sclerosis (RRMS).
This is a a dose and frequency (but not route of administration) blinded, prospective,
 randomized, dose-ranging study in patients with RRMS who have received natalizumab for at
 least 12 months according to the local prescribing guidelines. The study will explore dosing
 of natalizumab by subcutaneous and intravenous routes. Participants will be randomly assigned
 to 1 of 6 dosing regimens, blinded to natalizumab dose, but not route, for 60 weeks of
 treatment.
Key Inclusion Criteria:

 -  Ability to provide written informed consent

 -  Subjects of childbearing potential must practice effective contraception during the
 study

 -  A documented diagnosis of Relapsing Remitting Multiple Sclerosis (RRMS)

 -  Free of MS relapse for 12 months prior to randomization

 -  Treatment with natalizumab for a minimum of 12 months immediately prior to
 randomization.

 -  In the 12 months prior to commencing natalizumab, subject must have experienced a
 minimal level of disease activity as defined by 2 or more documented clinical relapses
 OR 1 relapse and documented MRI activity, defined by the presence of at least 1 Gd
 enhancing lesion on MRI, unrelated to the relapse.

 Key Exclusion Criteria:

 -  Known history of Human Immunodeficiency Virus (HIV), hepatitis C and/or hepatitis B
 virus

 -  Positive for anti-natalizumab antibodies at screening

 -  MRI positive for Gd-enhancing lesions at study entry

 -  Subjects for whom MRI is contraindicated

 -  History of any clinically significant cardiac, endocrinologic, hematologic, hepatic,
 immunologic, metabolic (including diabetes), urologic, pulmonary, neurologic (except
 for RRMS), dermatologic, psychiatric, renal, or other major disease

 -  History of malignant disease, including solid tumors and hematologic malignancies
 (with the exception of cured basal cell and squamous cell carcinomas of the skin)

 -  History of transplantation or any anti-rejection therapy

 -  History of severe allergic or anaphylactic reactions or known hypersensitivity to any
 drug

 -  A clinically significant infectious illness within 30 days prior to screening or
 progressive multifocal leukoencephalopathy (PML) or other opportunistic infections at
 any time

 -  Signs or symptoms suggestive of any serious infection, based on medical history,
 physical examination or laboratory testing

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