The primary purpose of this study is to evaluate the pharmacokinetics (PK) and pharmacodynamics (PD) of ublituximab in participants ages 10 to less than (\<)18 years and body weight greater than or equal to (≥)25 kilograms (kg) to less than or equal to (≤)40 kg with RMS (Part A) and to evaluate the non-inferiority of ublituximab compared with fingolimod in pediatric RMS participants with body weight ≥ 25 kg (Part B). The study will further evaluate long-term safety and efficacy of ublituximab in RMS in pediatric participants during its extension period (Part C).
Diagnosis of RMS.
EDSS at screening: 0-5.5, inclusive.
Neurologic stability for ≥ 30 days prior to screening, and between screening and Week 1 Day 1 (W1D1).
Known presence or suspicion of other neurologic disorders that may mimic MS.
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).
High dose intravenous immunoglobulin (IVIG) or subcutaneous IG (SCIG) within 2 months prior to W1D1.
Treatment with anti-CD20 or other B cell directed treatment at any time.
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Treatment groupsSee each treatment group below.