FDA approves Imaavy as first treatment specifically indicated for wAIHA

The US FDA has approved Imaavy (nipocalimab-aahu) as the first FDA-approved therapy for warm autoimmune hemolytic anemia (wAIHA). Johnson & Johnson (NYSE: JNJ) received the approval for adults and pediatric patients aged 12 and older who are currently or previously treated with corticosteroids. The decision, which followed FDA Priority Review, marks Imaavy's second approved indication after generalized myasthenia gravis (gMG) in April 2025.

Imaavy is administered intravenously at 30 mg/kg every four weeks. It functions as an immunoselective neonatal Fc receptor (FcRn) blocker: by occupying FcRn, it diverts endocytosed IgG — including pathogenic autoantibodies — toward lysosomal degradation rather than recycling, thereby reducing circulating IgG levels while preserving B-cell function, the company said.

The approval is supported by the Phase II/III ENERGY trial (NCT04119050), a multicenter, randomized, double-blind, placebo-controlled study in 115 adults with wAIHA. The primary endpoint was durable hemoglobin (Hgb) response, defined as Hgb ≥10 g/dL with an increase from baseline of ≥2 g/dL sustained for at least 28 days from Week 16, without rescue therapy. Approximately three times as many patients receiving the approved dose achieved this endpoint versus placebo by 24 weeks, Johnson & Johnson reported. A mean Hgb increase of 1 g/dL was observed at Week 1, and a 3.5-point improvement in Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) score versus placebo was reported at Week 24. The most common adverse reactions (≥10%) were peripheral edema, diarrhea, and fever.

In wAIHA, pathogenic IgG autoantibodies bind to and destroy red blood cells, causing severe anemia and fatigue. Prior to this approval, disease management relied on corticosteroids and immunosuppressants. Nipocalimab's FcRn mechanism underpins J&J's broader pipeline across rheumatologic, rare autoantibody, and maternal-fetal diseases, with Fast Track designations now spanning six indications including systemic lupus erythematosus.

Imaavy enters a wAIHA landscape where rituximab — an anti-CD20 monoclonal antibody used off-label — has served as the de facto second-line standard of care. The most advanced pipeline competitor is Sanofi's rilzabrutinib, an oral Bruton's tyrosine kinase (BTK) inhibitor with FDA Breakthrough Therapy designation in wAIHA and an active Phase III trial (NCT07086976), offering a mechanistically distinct and orally administered alternative. As noted in the broader FcRn inhibitor field, Imaavy is now one of three FDA-approved FcRn blockers, alongside argenx's efgartigimod and UCB's rozanolixizumab.

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