Long-term use of efgartigimod alfa in treating a young adult with childhood-onset systemic lupus erythematosus and generalized myasthenia gravis

Background

Patientis with myasthenia gravis (MG) are at increased risk of other autoimmune disorders, such as systemic lupus erythematosus (SLE). The neonatal Fc receptor (FcRn) antagonist, efgartigimod alfa (EFG-α), is effective in generalized MG (gMG) by a mechanism that decreases levels of IgG, including pathological autoantibodies. Although approved in Japan for gMG in 2022, its efficacy for other autoimmune disorders and the effects of long-term use of EFG-α for gMG in children and young adults remain to be elucidated.

Case

A 10-year-old girl diagnosed with SLE developed gMG 2 years later. Despite intensive therapy, she also had myasthenic crisis and two recurrences. Moreover, the anti-acetylcholine receptor (AChR) antibody titer remained high, making it difficult to reduce the prednisolone (PSL) dose to below 12.5 mg/day. Eight years later, she had a flare of SLE and was treated with pulse methylprednisolone followed by EFG-α to reduce the PSL dose. A total of six cycles of EFG-α (10 mg/kg) were administered, with four infusions per cycle (one infusion per week) over a period of one and a half years. Consequently, the quantitative MG (QMG) score, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), and anti-double-stranded DNA (dsDNA) antibody titer remained low. Furthermore, the prolonged administration of EFG-α resulted in a reduction in the dosage of prednisolone, which led to improvement in the patient's obesity.

Conclusion

EFG-α may be effective not only for MG but also for SLE, maintaining low disease activity and antibody levels. Long-term use could reduce steroid requirement, and thus decrease adverse effects. Expanding the indication of EFG-α to other autoimmune diseases and considering its use in pediatric patients are recommended.