Johnson & Johnson’s nipocalimab-aa4hu, marketed as IMAAVY, has been approved by the U.S. Food and Drug Administration (FDA) for generalized myasthenia gravis (gMG), according to a press release published Wednesday.
Niopocalimab is also being developed as a therapy for hemolytic disease of the fetus and newborn (HDFN), and a phase 3 clinical trial is currently underway.
Nipocalimab in myasthenia gravis
Nipocalimab works by blocking the neonatal FcRn, a key protein that prevents immunoglobulin G (IgG) antibodies — including dangerous autoantibodies — from being broken down. By lowering levels of IgG, it addresses a root cause of several autoantibody diseases.
In the Vivacity-MG3 trial for gMG, nipocalimab delivered rapid and sustained symptom relief and control, with improvements lasting up to 20 months in an ongoing extension study. These results underscore the drug’s potential to offer long-lasting benefits in other IgG-mediated conditions where durable antibody suppression could prevent life-threatening complications before birth.
The approval covers both anti-acetylcholine receptor and anti-muscle-specific kinase antibody-positive patients, who make up over 90% of the gMG population. Adolescents aged 12 to 17 also showed strong responses in a separate pediatric trial, further supporting its safety and effectiveness across age groups.
Nipocalimab in HDFN
The phase 3 AZALEA trial studying nipocalimab in HDFN began in December 2023. Phase 2 showed promising results,—92% of pregnancies involved in the trial resulted in live births, and only 85% required intrauterine transfusions.
Read more about HDFN treatments
In February, the FDA granted Breakthrough Therapy Designation to nipocalimab for treating alloimmunized pregnant individuals at high risk of severe HDFN. This designation is based on the positive results from the UNITY trial and aims to expedite the drug’s development and review process. Nipocalimab is currently on track to become the first approved therapy for HDFN.
Beyond its therapeutic action, nipocalimab is designed to preserve other immune system functions — a key feature for both pregnant patients and newborns, where broad immunosuppression would be unsafe.
Johnson & Johnson has begun global regulatory submissions for nipocalimab in gMG and continues trials in pregnancy-related conditions. Its FDA approval now marks a major step toward new hope for families facing serious, antibody-driven diseases with few or no current treatment options.
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