Nipocalimab (Imaavy)

Nipocalimab is a third FcRn-blocking antibody for generalized myasthenia gravis, joining this site's efgartigimod and rozanolixizumab pages — FDA-approved in April 2025 for the broadest antibody-positive population of any FcRn blocker at first approval, down to age 12. It's also the newest case of a pattern this site's efgartigimod page already describes: an FcRn blocker expanding into a second, unrelated autoimmune disease. In August 2026, the FDA approved nipocalimab as the first treatment ever approved specifically for warm autoimmune hemolytic anemia — a genuinely new indication, not a me-too label expansion.

A third FcRn blocker, and where it differs

This site's efgartigimod and rozanolixizumab pages both describe blocking the neonatal Fc receptor (FcRn) to clear a generalized myasthenia gravis (gMG) patient's own disease-driving IgG antibodies faster than the body normally would. Nipocalimab, developed by Johnson & Johnson (Janssen Biotech), works on the same target — a fully human monoclonal antibody against FcRn, independently developed from both argenx's efgartigimod and UCB's rozanolixizumab — but is described by its developer as "immunoselective," engineered to reduce pathogenic IgG while leaving other immune functions, including B-cell activity, comparatively undisturbed. The FDA approved it as Imaavy (nipocalimab-aahu) on 29 April 2025.

Vivacity-MG3

Nipocalimab's gMG approval rested on Vivacity-MG3 (Antozzi C, Vu T, Ramchandren S, et al., "Safety and efficacy of nipocalimab in adults with generalised myasthenia gravis (Vivacity-MG3): a phase 3, randomised, double-blind, placebo-controlled study," Lancet Neurol 2025;24(2):105-116, PMID 39862879, DOI: 10.1016/S1474-4422(24)00498-8), a trial conducted at 81 sites across 17 countries. 199 adults with gMG inadequately controlled on standard-of-care therapy were randomized to nipocalimab (30mg/kg loading dose, then 15mg/kg every 2 weeks) or placebo infusions for 24 weeks. In the trial's primary efficacy population — 153 antibody-positive patients — the least-squares mean change in MG-ADL score from baseline was -4.70 with nipocalimab versus -3.25 with placebo, a placebo-corrected difference of 1.45 points (95% CI -2.38 to -0.52, P=0.0024). Adverse-event rates were similar between arms, including infection rates (43% in both groups).

The broadest population at first approval, down to age 12

Where this site's efgartigimod page describes an original 2021 approval limited to AChR-antibody-positive adults, and rozanolixizumab's 2023 approval covered AChR- or MuSK-positive adults, nipocalimab's original approval already covered both AChR- and MuSK-antibody-positive patients — and extended down to age 12, making it, at launch, the FcRn blocker approved for the widest gMG population of the three, described by the company as covering roughly 95% of people living with the disease. Antibody-negative ("triple seronegative") gMG remains outside nipocalimab's approved label, the same gap efgartigimod's own May 2026 label expansion closed for that drug specifically.

August 2026: the first-ever approved treatment for a second, unrelated disease

On 24 August 2026, the FDA approved Imaavy for warm autoimmune hemolytic anemia (wAIHA) in patients 12 and older currently or previously treated with corticosteroids — a rare blood disorder in which autoantibodies destroy red blood cells faster than the body can replace them, mechanistically unrelated to myasthenia gravis beyond both being driven by pathogenic IgG. The FDA describes this as the first treatment ever proven safe and effective specifically for wAIHA. The approval rested on the Phase 2/3 ENERGY trial, a randomized, double-blind, placebo-controlled study in which roughly three times as many nipocalimab-treated patients achieved a durable hemoglobin response by 24 weeks as on placebo, with a measurable hemoglobin increase reported as early as week 1. As of this review, ENERGY's full results have been disclosed via company and FDA announcements and a scientific-congress presentation rather than a peer-reviewed journal publication — worth checking for a completed publication if the underlying trial data matters to you.

Current status

Johnson & Johnson markets Imaavy for both approved indications, competing directly with efgartigimod and rozanolixizumab in gMG while holding, as of this review, the only FDA approval of any kind for wAIHA. The most common adverse reactions across nipocalimab's trials were infections and headache; like this site's other two FcRn-blocker pages, its label carries no boxed warning, only a general infection-risk warning tied to reduced circulating IgG. As a specialty immunology and hematology biologic administered by infusion under medical supervision, nipocalimab has no wellness, bodybuilding or grey-market presence of any kind.