Myasthenia gravis (MG) is a rare, heterogeneous, neuromuscular disease characterized by fluctuating, fatigable muscle weakness. MG is caused by pathogenic autoantibodies that impair cholinergic transmission in the postsynaptic membrane at the neuromuscular junction and impair or prevent muscle contraction. Nipocalimab (also referred to as JNJ-80202135 or M281) is a fully human, aglycosylated immunoglobulin (Ig)G1 monoclonal antibody (mAb) designed to selectively bind, saturate, and block the IgG binding site on the endogenous neonatal Fc receptor (FcRn). This study will consist of a screening phase (up to 4 weeks), treatment phase (a 24-week double-blind placebo-controlled phase, and an open-label extension [OLE] phase [up to 2 years]) and a follow-up safety visit (up to 8 weeks after last infusion of study intervention). Efficacy evaluations will include assessments such as Myasthenia Gravis - Activities of Daily Living (MG-ADL) score. Safety evaluations (such as adverse events, physical examination, vital signs, electrocardiogram [ECG], and clinical laboratory tests) will be performed. The overall duration of study will be up to 4 years and 8 months.

Myasthenia gravis (MG) is a rare, heterogeneous, neuromuscular disease characterized by fluctuating, fatigable muscle weakness. MG is caused by pathogenic autoantibodies that impair cholinergic transmission in the postsynaptic membrane at the neuromuscular junction and impair or prevent muscle contraction. Nipocalimab (also referred to as JNJ-80202135 or M281) is a fully human, aglycosylated immunoglobulin (Ig)G1 monoclonal antibody (mAb) designed to selectively bind, saturate, and block the IgG binding site on the endogenous neonatal Fc receptor (FcRn). This study will consist of a screening phase (up to 4 weeks), treatment phase (a 24-week double-blind placebo-controlled phase, and an open-label extension \[OLE\] phase \[up to 2 years\]) and a follow-up safety visit (up to 8 weeks after last infusion of study intervention). Efficacy evaluations will include assessments such as Myasthenia Gravis - Activities of Daily Living (MG-ADL) score. Safety evaluations (such as adverse events, physical examination, vital signs, electrocardiogram \[ECG\], and clinical laboratory tests) will be performed. The overall duration of study will be up to 4 years and 8 months.