J&J’s Imaavy Wins FDA Nod for Rare Blood Disorder wAIHA

The US Food and Drug Administration (FDA) has expanded the label indication of Johnson & Johnson’s (J&J) Imaavy (nipocalimab-aahu) to treat warm autoimmune haemolytic anaemia (wAIHA), a rare and sometimes life-threatening autoantibody disorder. Announced on 25 August 2026, the approval makes Imaavy the first and only US-approved medicine specifically for wAIHA, further reinforcing J&J’s $5 billion peak sales target for the drug.

The expanded approval covers adults and paediatric patients aged 12 years and older currently or previously treated with corticosteroids. Approval was based on data from the Phase II/III ENERGY study, presented in June 2026, in which Imaavy demonstrated a durable red blood-cell count versus placebo after 24 weeks, meeting the trial’s primary endpoint. wAIHA patients typically have low red blood-cell counts and low haemoglobin levels because their immune system mistakenly attacks and destroys red blood cells, with approximately 1-3 new people per 100,000 affected each year.

Imaavy is an immunoselective treatment that blocks the neonatal Fc receptor (FcRn), reducing circulating immunoglobulin G antibodies that drive disease while preserving B-cell function. The FDA first authorised Imaavy in April 2025 for generalised myasthenia gravis in certain adults and paediatric patients aged 12 and older. J&J acquired the drug through its $6.5 billion acquisition of Momenta Pharmaceuticals in 2020, and is also evaluating it in Sjogren’s disease, systemic lupus erythematosus and haemolytic disease of the foetus and newborn. The wAIHA approval places Imaavy in direct competitive tension with Argenx’s Vyvgart (efgartigimod), already approved for wAIHA and generalised myasthenia gravis.

The commercial signal is J&J building Imaavy toward blockbuster status through progressive rare-disease indication expansion, with wAIHA the second major approval in less than 18 months. FcRn inhibitor competition intensifies as J&J and Argenx compete across overlapping autoimmune indications. Expect UCB, Alexion (AstraZeneca), Momenta legacy successors and other FcRn developers to sharpen their positioning as rare autoimmune competition consolidates through 2027.

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