Clinicians in Europe may soon gain access to a first-in-class neonatal Fc receptor (FcRn) inhibitor for generalized myasthenia gravis (gMG). 

Imaavy (nipocalimab; Janssen-Cilag International) received a positive opinion from the European Medicines Agency (EMA) for use as an add-on to standard therapy for treating gMG in adults and adolescents aged 12 years or older who are anti-acetylcholine receptor or anti-muscle-specific tyrosine kinase antibody positive.

Myasthenia gravis is an autoimmune neuromuscular disorder characterized by weakness and rapid fatigue of voluntary muscles. The condition is caused by pathogenic IgG autoantibodies that interfere with neuromuscular transmission at the postsynaptic membrane. In gMG, these autoantibodies target key proteins involved in neuromuscular junction function, leading to muscle weakness that can affect breathing, swallowing, and mobility.

Nipocalimab is a fully human IgG1 monoclonal antibody that selectively binds to the FcRn, thereby decreasing the levels of circulating IgG, including pathogenic IgG autoantibodies. This targeted mechanism reduces the burden of disease-causing antibodies while maintaining the natural recycling pathway for albumin.

In clinical trials, nipocalimab demonstrated positive efficacy when added to standard therapy in both adults and adolescents with gMG.

In the phase 3 Vivacity-MG3 study, which included 196 adults with inadequately controlled disease, patients received either nipocalimab (30 mg/kg loading dose followed by 15 mg/kg every 2 weeks) or placebo infusions for 24 weeks, both added to standard-of-care therapy. Those receiving nipocalimab showed significantly greater improvement in Myasthenia Gravis Activities of Daily Living and Quantitative Myasthenia Gravis scores compared with placebo. Additionally, nipocalimab plus standard care reduced functional disability as rated by patients and decreased disease severity as assessed by qualified physicians, compared with placebo plus standard care.

The Vibrance-MG study evaluated safety and efficacy of nipocalimab in 12 pediatric patients with gMG aged 2 to < 18 years old who also received standard of care therapy. Results showed a significant reduction in total serum IgG and clinically meaningful improvement in muscle strength and daily function, consistent with results seen in adult trials. 

Across these trials, Imaavy was well tolerated with an acceptable safety profile, representing a new effective treatment for both adult and pediatric patients with gMG. Its most common side effects include increased lipids, decreased serum albumin, muscle spasm, and peripheral edema.

Imaavy will be available as a concentrate for solution for infusion in 300 mg/1.62 ml and 1200 mg/6.5 ml presentations. Treatment should be initiated and monitored by physicians experienced in neuromuscular disorders.

Detailed recommendations for Imaavy use will be described in the summary of product characteristics, which will be published on the EMA website after the European Commission grants marketing authorization.