Inclusion Criteria:  Body weight ≥ 50 kg Diagnosis of RRMS in accordance with the International Pediatric Multiple Sclerosis Study Group (IPMSSG) criteria for pediatric MS, Version 2012, or McDonald criteria 2017 EDSS at screening: 0-5.5, inclusive Neurologic stability for ≥ 30 days prior to screening, and between screening and Day 1 At least one MS relapse during the previous year or two MS relapses in the previous 2 years or evidence of at least one Gd enhancing lesion on MRI within 6 months  Exclusion Criteria:  Known presence or suspicion of other neurologic disorders that may mimic MS Significant uncontrolled somatic diseases, known active infection or any other significant condition that may preclude patient from participating in the study Patient with severe cardiac disease or significant findings on the screening ECG