FDA Expands Approval of J&J’s Imaavy to Include Rare Blood Disease

Rare Daily Staff

The U.S. Food and Drug Administration has approved Johnson & Johnson’s Imaavy for adults and adolescents ages 12 and older with warm autoimmune hemolytic anemia, the first FDA-approved therapy for the rare and potentially life-threatening condition.

The approval is for use in patients who are currently or were previously treated with corticosteroids.

Warm autoimmune hemolytic anemia (wAIHA) is a condition in which autoantibodies attack and destroy red blood cells. It can cause severe anemia, debilitating fatigue and complications including blood clots, kidney failure and infection. Until now, treatment has largely relied on corticosteroids and broader immunosuppressive medicines.

Imaavy blocks the neonatal Fc receptor, or FcRn, reducing circulating immunoglobulin G autoantibodies that drive red blood cell destruction while preserving B-cell function.

“Patients may cycle through periods where they start to feel like themselves again — and then their hemoglobin drops, the exhaustion returns, and they’re back to square one,” said Karen Jones, president and executive director of the patient advocacy organization wAIHA Warriors. “For the first time, our community has a treatment specifically for our disease.”

The FDA approval was based on the phase 2/3 ENERGY trial, a randomized, double-blind, placebo-controlled study involving 115 adults with wAIHA. At the approved intravenous dose given every four weeks, approximately three times as many Imaavy-treated patients achieved a durable hemoglobin response by Week 24 compared with placebo. The study defined that response as hemoglobin reaching at least 10 g/dL and increasing by at least 2 g/dL from baseline for at least 28 days without rescue therapy.

Patients receiving Imaavy had a mean hemoglobin increase of 1 g/dL after one week. The company also reported a 3.5-point greater improvement, versus placebo, on the FACIT-Fatigue scale at Week 24. Higher scores indicate less fatigue.

David Kuter, a Massachusetts General Hospital physician and Harvard Medical School professor who served as a consultant to Johnson & Johnson, said the study showed that targeting pathogenic IgG “can meaningfully change the treatment paradigm” for the disease.

Johnson & Johnson said Imaavy’s safety profile in the wAIHA study was consistent with its prior experience in generalized myasthenia gravis, another antibody-mediated disease for which the drug was approved in April 2025.

The most common adverse reactions among wAIHA patients were peripheral edema, diarrhea and fever. The prescribing information also warns of potentially serious infections, allergic reactions and infusion-related reactions. People receiving the therapy should not receive live vaccines.