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.

The pathogenesis of multiple sclerosis is multifaceted and not fully investigated, but it is now clear that each patient has their own ratio of inflammation and neurodegeneration severity. Given the available evidence base, understanding of the pathogenesis underlying secondary progression, and accumulated clinical experience, it is important not only to make a timely diagnosis and prescribe adequate therapy, but also to monitor for continued progression in order to revise treatment with the aim of preventing patient disability. This publication describes a clinical case of a patient with secondary progressive multiple sclerosis (SPMS) who received therapy with an anti-CD20 monoclonal antibody infusion. The patient showed complete suppression of activity and no exacerbations, but despite this, there was a gradual progression on the EDSS scale from 4.5 to 6.0 points over 3 years of therapy. In this regard, the patient was transferred to therapy with siponimod, against which a decrease to 5.5 points was noted within a few months. At the time of publication, this indicator has remained stable for 3 years, indicating that the main goal of therapy for SPMS – preventing secondary progression – has been achieved.

Therefore, when treating patients with SPMS and ongoing secondary progression, even with complete suppression of activity and no exacerbations, including against the background of infusion therapy with anti-CD20 monoclonal antibody drugs, it is necessary to consider switching to siponimod therapy.