Given the recent trends and accumulating evidence supporting the advantages of anti-B-cell therapy, early initiation of this treatment modality in multiple sclerosis (MS) has become increasingly relevant for controlling disease activity and reducing the risk of disability progression. The therapeutic landscape for MS continues to expand, with the introduction of a new anti-CD20 molecule – divozilumab – approved in Russia in 2023, which has shown efficacy in patients with MS. When selecting a treatment strategy for MS patients, clinical decisions should be based on the evidence from individual clinical trials and real-world experience, especially for patients with progressive forms of the disease.

Among intravenous anti-CD20 therapies, ocrelizumab currently holds a clinical advantage due to the breadth of real-world experience supporting its use.

In recent years, the incidence of multiple sclerosis (MS) has increased in the pediatric population. As there are no separate clinical guidelines for the treatment of pediatric MS and therapeutic options have expanded, it is important to discuss and establish new protocols for the treatment of MS in children and adolescents. This article presents a series of clinical cases of the use of ofatumumab in patients under 18 years of age with a relapsing-remitting MS (RRMS).

In the first observation, a 16-year-old female patient with RRMS was switched to ofatumumab therapy due to persistent clinical and radiological activity of the disease during dimethyl fumarate therapy. After the first injection, hyperthermia of up to 38.6 °C and cephalgia were observed, which resolved on the background of symptomatic therapy. No adverse events occurred with subsequent injections, and the patient had clinical and radiological remission during the six-month use of the drug.

In the second observation, a 17-year-old female patient with a four-year history of the disease showed resistance to first-line therapy (interferon β1a and glatiramer acetate), so therapy was switched to ofatumumab. After the first injection, persistent hyperthermia of up to 39.3 °C was observed for two days, therefore, premedication with antipyretic and antihistamine medication was performed for the next two injections. No further adverse events were recorded, the therapy was well tolerated, and premedication was not required. The clinical remission of the disease lasted for six months and the results of the control MRI showed no signs of disease activity.

In the third observation, ofatumumab therapy was initiated in a 17-year-old patient with rapidly progressive MS. No adverse events were recorded during the 9-month treatment, no signs of the disease activity were detected on the control MRI, and a decrease in the size of some foci was observed.

Thus, high short-term efficacy, good tolerability and safety of ofatumumab in the treatment of MS in patients under 18 years of age were demonstrated, which are consistent with the results of the use of the drug in the adult population; no unexpected adverse events were observed. The subcutaneous route of administration contributed to improved patients’ adherence to therapy.