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FDA approves nipocalimab, a new FcRn blocker for generalized myasthenia gravis

On April 30, 2025, the U.S. Food and Drug Administration (FDA) approved nipocalimab, a human neonatal Fc receptor (FcRn)-blocking monoclonal antibody (mAb), for the treatment of generalized myasthenia gravis (gMG). The approval was based on pivotal Phase III results demonstrating sustained disease control across a broad patient population, including adults and adolescents aged 12 and older who are positive for anti-acetylcholine receptor (AChR) or anti-muscle-specific kinase (MuSK) antibodies.1

Addressing the unmet need in myasthenia gravis

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness in the voluntary muscles. In individuals with MG, autoantibodies target components of the neuromuscular junction, most commonly nicotinic AChRs, preventing communication between nerves and muscles.2 The estimated number of people affected by MG varies, ranging from 5 to 14 people per 100,000; the disease can occur at any age across all ethnic groups, although it most commonly affects women under the age of 40 and men over the age of 60.3

Current pharmacological interventions for MG include agents that modulate neuromuscular transmission, such as pyridostigmine and amifampridine, and immunosuppressive agents, such as corticosteroids. However, these agents are associated with significant adverse effects (AEs), such as gastrointestinal AEs and hepatotoxicity, respectively. Efgartigimod and rozanolixizumab are FcRn inhibitors that are approved for the treatment of MG, but clinical trials reported a subset of patients who responded poorly.4 There is a need for novel targeted therapies with fewer AEs that are efficacious in a broad population of patients with MG.

Nipocalimab: a novel FcRn blocker

Nipocalimab is a fully human mAb that blocks the interaction between FcRn and immunoglobulin G (IgG) antibodies, causing prolonged IgG depletion and reducing the autoimmune attack on AChRs. FcRn antagonists have shown the ability to reduce autoantibody-mediated damage in MG and other autoimmune conditions, highlighting the therapeutic potential of nipocalimab.2 Nipocalimab is the first FcRn antagonist to show sustained disease control in a broad population of people living with gMG.1

Pivotal clinical trials: Vivacity-MG3 and Vibrance

The approval of this agent is based on data from two trials: the Phase III Vivacity-MG3 trial (NCT04951622) and the Phase II/III Vibrance trial (NCT05265273). The 24-week double-blind placebo-controlled Vivacity-MG3 trial investigated the safety and efficacy of nipocalimab in adults with gMG. A total of 199 patients, including 153 antibody-positive patients, were randomized 1:1 to receive nipocalimab or placebo.5 The findings revealed superior disease control in patients receiving nipocalimab plus standard of care (SoC), as measured by the Myasthenia Gravis – Activities of Daily Living (MG-ADL) scale. This means patients could regain essential daily functions, such as chewing, swallowing, speaking, and breathing. Additionally, autoantibody levels were reduced by 75% from the first dose of nipocalimab and throughout the 24-week monitoring period. The ongoing open-label extension has shown that improvements were maintained at a follow-up of 20 months.1 Most AEs were mild to moderate, including infections and headache, and their incidence was similar between groups. Serious AEs were reported in 9% of patients in the nipocalimab arm and 14% of patients in the placebo arm.5

The Phase II/III Vibrance trial (NCT05265273) investigated nipocalimab in adolescents (aged 12-17 years) with anti-AChR positive gMG. The primary endpoint of the study was reduced total serum IgG, and secondary endpoints included improvements in the MG-ADL and Quantitative Myasthenia Gravis (QMG) scales. Nipocalimab combined with SoC achieved the primary endpoint by reducing total serum IgG by 69%, and met secondary endpoints related to disease activity. Four out of five patients reached minimal symptoms (MG-ADL score 0–1) by the end of treatment. The drug was well-tolerated over six months, with no serious AEs or treatment discontinuations, consistent with findings from the Vivacity-MG3 trial.6

Implications and future outlooks

The approval of nipocalimab represents a major step forward in the treatment of patients with anti-AChR or anti-MuSK antibody-positive gMG, particularly those who do not respond to currently available therapies. As more targeted treatments like FcRn antagonists become available in clinical practice, they have the potential to transform the SoC by offering improved efficacy and tolerability. Ongoing studies are exploring their potential in other autoimmune diseases, highlighting the need for continued research to better understand their long-term impact and place in the broader treatment landscape.

References

  1. Johnson & Johnson. Johnson & Johnson receives FDA approval for IMAAVYTM (nipocalimab-aahu), a new FcRn blocker offering long-lasting disease control in the broadest population of people living with generalized myasthenia gravis (gMG). Available here. (Last accessed: 01/05/2025).
  2. Bussel JB, Cines DB, Blumberg RS. Neonatal Fc receptor — biology and therapeutics. N Engl J Med. 2025 Apr 23;392(16):1621-35.
  3. OASH. Myasthenia gravis. Available here. (Last accessed 01/05/2025).
  4. Kaminski HJ, Sikorski P, Coronel SI, et al. Myasthenia gravis: the future is here. J Clin Invest. 2024 Jun 17;134(12):e179742.
  5. Antozzi C, Vu T, Sindhu Ramchandren, et al. Safety and efficacy of nipocalimab in adults with generalised myasthenia gravis (Vivacity-MG3): a phase 3, randomised, double-blind, placebo-controlled study. The Lancet Neurology. 2025 Jan;24(2):105–16.
  6. Johnson & Johnson. Nipocalimab demonstrates sustained disease control in adolescents living with generalized myasthenia gravis in Phase 2/3 study. Available here. (Last accessed: 01/05/2025).

Written by Karina Tundondjo

Edited by Hannah Elkheir and Anya Dragojlovic Kerkache