Study to Assess Effects of Ublituximab in Pediatric Participants With Relapsing Forms of Multiple Sclerosis

Exclusion Criteria

• •1. Known presence or suspicion of other neurologic disorders that may mimic MS.
• •2. Prior treatments:
• •1. Systemic corticosteroids (\>0.1 milligrams/kilogram/day \[mg/kg/day\], or \>5 milligrams/day \[mg/day\] of prednisone equivalent) or adrenocorticotropic hormone (ACTH) within 30 days prior to the screening MRI scan (note: Topical, ophthalmic, or inhaled corticosteroids are permitted).
• •2. High dose intravenous immunoglobulin (IVIG) or subcutaneous IG (SCIG) within 2 months prior to W1D1.
• •3. Treatment with anti-CD20 or other B cell directed treatment at any time.
• •4. Treatment with alemtuzumab, cladribine, cyclophosphamide, mitoxantrone at any time.
• •1. Treatment with fingolimod or other sphingosine-1 phosphate-1 (S1P1) modulators at any time.
• •2. The following antiarrhythmic drugs at Screening: Class Ia anti-arrhythmics.
• •1\. If the absolute lymphocyte count (ALC) is outside the specified range the participant will not be eligible to receive ublituximab in Part C.