Claseprubart, an investigational antibody therapy, led to rapid and clinically meaningful improvements in adults with acetylcholine receptor antibody-positive generalized myasthenia gravis (MG) while maintaining a favorable safety profile, according to results from the Phase 2 MaGic study presented at the 2026 American Academy of Neurology annual meeting in Chicago.
In generalized MG, the immune system disrupts communication between nerves and muscles; the classical complement pathway, part of the immune system, plays a central role in this process. Claseprubart is designed to block this pathway by targeting the active form of the C1s protein, potentially reducing damage without broadly suppressing the immune system.
This randomized, double-blind, placebo-controlled study enrolled 65 adults with acetylcholine receptor antibody-positive generalized MG. Participants were assigned evenly to receive 300 mg of claseprubart every two weeks, 600 mg every two weeks or a placebo for 13 weeks.
Researchers evaluated safety along with several measures of disease severity, including activities of daily living, muscle strength and overall symptom burden.
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“With a favorable safety profile, claseprubart demonstrated rapid, statistically significant, and clinically meaningful improvements in MG,” the study’s authors stated.
At 13 weeks, patients receiving claseprubart showed significantly greater improvement in daily functioning compared with placebo. MG activities of daily living scores improved by 4.6 points in the 300 mg group and 5.4 points in the 600 mg group, compared with 2.8 points with placebo. Notably, improvement was seen as early as one week after starting treatment, suggesting a fast onset of action.
Measures of muscle strength and overall disease impact also improved. Quantitative MG scores improved by 4.4 and 4.5 points in the 300 mg and 600 mg groups, respectively, compared with 2.0 points in the placebo group. Minimal symptom expression was achieved by 37% and 27% of patients in the treatment groups, versus 14% with placebo. MG Composite scores improved by 8.7 and 8.6 points with claseprubart, compared with 3.1 points in the placebo group.
Safety findings were reassuring. No serious adverse events, serious bacterial infections or autoimmune complications were reported. Injection site reactions were uncommon and mostly mild to moderate.
For patients, these results suggest the possibility of a new treatment that can improve strength and daily function quickly without major safety tradeoffs. A larger Phase 3 study is being planned to confirm these findings and better understand long-term effects.
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