ABSTRACT Nipocalimab is a fully human immunoglobulin G (IgG)1 monoclonal antibody (mAb) designed to selectively block the IgG binding site of neonatal fragment crystallizable receptor (FcRn) to inhibit IgG recycling and decrease circulating IgG, including pathogenic IgG autoantibodies (such as antiacetylcholine receptor, anti‐muscle‐specific kinase, and anti‐low‐density lipoprotein‐related protein 4 antibodies in generalized myasthenia gravis [gMG]). A mechanistic model, integrating serum nipocalimab concentrations, FcRn occupancy, and total serum IgG data from five phase 1 studies in healthy adult participants and one phase 2 (Vivacity‐MG) study in adult participants with gMG, was developed. The relationship between total serum IgG reduction and placebo‐corrected MG‐Activities of Daily Living score change from baseline in participants with gMG was also characterized. Nipocalimab exhibited nonlinear target (FcRn)‐mediated disposition, causing rapid, reversible, and concentration‐dependent FcRn occupancy and IgG reduction (up to 85%) in healthy participants and participants with gMG. The PK of nipocalimab after a single intravenous (IV) administration is consistent with that after repeated IV administrations, with no accumulation following every 2 weeks (Q2W) dosing. The PK of nipocalimab and its effect on IgG reduction were similar between healthy participants and participants with gMG. Model‐based simulations indicated that the IV dose of 15 mg/kg Q2W, starting 2 weeks after a 30 mg/kg IV loading dose, was the lowest Q2W maintenance dose predicted to achieve the target of 70% median of the average change in IgG reduction in participants with gMG and was the recommended dose for the pivotal phase 3 Vivacity‐MG3 study in a gMG population.