A Study to Evaluate Pharmacokinetics, Safety, Tolerability, Immunogenicity and Pharmacodynamic Effects of Subcutaneous Ocrelizumab Administration in Children and Adolescents With Relapsing-remitting Multiple Sclerosis (RRMS)

The main purpose of this study is to evaluate the pharmacokinetics (PK) of ocrelizumab administered subcutaneously (SC) in children and adolescents aged 10 to \

Inclusion Criteria: * Children and adolescents from 10 years to less than 18 years of age, at the time of baseline visit * Body weight ≥25 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 or 2024 * Neurologic stability for at least 30 days prior to screening, and between screening and baseline * Expanded Disability Status Scale (EDSS) score, 0-5.5, at screening * Must have received all childhood required vaccinations as per local/national recommendations for childhood vaccination against infectious diseases Exclusion Criteria: * Participants who are positive for aquaporin 4 (AQP4) or myelin oligodendrocyte glycoprotein (MOG) antibody are not eligible to participate in the study * Any known presence or suspicion of other neurologic disorders that may mimic multiple sclerosis (MS) * History or known presence of recurrent or chronic infection (e.g., human immunodeficiency virus \[HIV\], syphilis, tuberculosis \[TB\]) * Contraindications against SC injections or other conditions not suitable for SC injections, e.g., extremely thin SC fat layer * History of a severe allergic or anaphylactic reaction to humanized or murine monoclonal antibody or known hypersensitivity to any component of ocrelizumab solution * Contraindications to mandatory premedications (i.e., corticosteroids and histamines), including closed-angle glaucoma for antihistamines * Participants who have previously received treatment with B cell-targeted therapies, including ocrelizumab * Any previous treatment with alemtuzumab, anti-CD4, cladribine, mitoxantrone, daclizumab, laquinimod, total body irradiation, or bone marrow transplantation * Treatment with any investigational agent within 24 weeks of screening or 5 half-lives, whichever is longer (or longer if indicated by the PD action of the drug)