Ofatumumab in refractory anti-muscle-specific tyrosine kinase antibody-positive myasthenia gravis: a case report of successful salvage therapy and mechanistic insights.

Muscle-specific tyrosine kinase antibody-positive myasthenia gravis (MuSK-MG), a subtype of myasthenia gravis (MG), follows an acute and severe disease course with suboptimal responses to standard treatments. Ofatumumab is a fully humanized anti-CD20 monoclonal antibody that induces potent and sustained B-cell depletion. Nonetheless, there are few reports on its use in sequential therapy failure after the failure of conventional drug treatment in MuSK-MG patients, especially in the Asian population. We report a 32-year-old female patient with anti-MuSK antibody-positive myasthenia gravis who was treated with ofatumumab as a rescue therapy after failing multiple treatments such as intravenous immunoglobulin (IVIG), plasma exchange, and efgartigimod, progressed to a crisis state necessitating prolonged mechanical ventilation. After the addition of ofatumumab to the combination of tacrolimus and corticosteroids, the clinical symptoms were significantly improved, the patient was successfully weaned from ventilator-assisted ventilation, the bulbar function was improved, and the limb muscle strength was significantly restored, and the patient was finally discharged uneventfully. This case is the first report of ofatumumab successfully treating refractory MuSK-MG in China, providing real-world evidence for its pivotal role in the treatment sequence. It also suggests that its characteristics, such as subcutaneous administration and low immunogenicity, may render it particularly suitable for high-risk patients, including those with concurrent infections.