J&J’s anti-FcRn mAb Imaavy takes FDA Priority Review for wAIHA

Johnson & Johnson (NYSE: JNJ) announced receipt of US FDA Priority Review for the supplemental Biologics License Application (sBLA) for Imaavy (nipocalimab-aahu), an anti-neonatal Fc receptor (FcRn) monoclonal antibody, for the treatment of warm autoimmune hemolytic anemia (wAIHA). The filing marks the first time any therapy has received Priority Review from the agency for this condition.

Priority Review shortens the FDA’s standard ten-to-twelve-month review timeline to approximately six months for medicines that may offer meaningful improvements in safety or effectiveness for serious conditions. Nipocalimab had previously received FDA Fast Track designation for wAIHA in July 2019 and Orphan Drug designation for the same indication in December 2019.

The sBLA is supported by data from the ENERGY trial, a multicenter, randomized, double-blind, placebo-controlled Phase 2/3 study in adults with wAIHA. The primary endpoint was durable hemoglobin response, defined as hemoglobin concentration of at least 10 g/dL and an increase from baseline of at least 2 g/dL sustained for a minimum of 28 days without rescue therapy. Johnson & Johnson reported that more patients treated with nipocalimab met this endpoint than those receiving placebo, and that fatigue — measured by the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) scale — also improved. The company has stated that full ENERGY results will be presented at a forthcoming medical conference; precise response rates, effect sizes, and p-values have not yet been disclosed in any public source identified at the time of this report.

Nipocalimab blocks FcRn, a receptor that recycles immunoglobulin G (IgG) antibodies and extends their half-life in circulation. By occupying FcRn, the drug accelerates IgG catabolism, reducing total circulating IgG including the pathogenic autoantibodies that drive red blood cell destruction in wAIHA. The mechanism is selective in that it does not directly deplete B cells or broadly suppress innate immune function, which distinguishes it from the corticosteroids, rituximab, and broad immunosuppressants that currently constitute off-label standard of care in this disease.

Imaavy is already FDA-approved — the agency cleared the product on April 29, 2025 for generalized myasthenia gravis (gMG) in adults and pediatric patients aged 12 years and older who are anti-acetylcholine receptor (AChR) or anti-muscle-specific tyrosine kinase (MuSK) antibody positive. The wAIHA sBLA therefore represents a label expansion for an approved molecule rather than an initial market entry.

Research context

wAIHA is a rare condition in which IgG autoantibodies bind to red blood cell surface antigens, triggering their destruction by the reticuloendothelial system and producing hemolytic anemia of variable severity. Incidence is estimated at one to three new cases per 100,000 persons annually, with a prevalence of approximately one in 8,000. The condition affects both sexes across all age groups, though incidence rises after age 50. Complications extend beyond anemia and include venous thrombotic events, acute renal failure, and infection risk. There are currently no FDA-approved drugs indicated for wAIHA.

Nipocalimab is also in development across a broader portfolio of IgG-mediated diseases. Active programs include studies in hemolytic disease of the fetus and newborn (HDFN), for which the molecule holds FDA Breakthrough Therapy designation granted in February 2024; fetal and neonatal alloimmune thrombocytopenia (FNAIT); Sjögren’s disease, which received Breakthrough Therapy designation in November 2024; systemic lupus erythematosus; and chronic inflammatory demyelinating polyneuropathy (CIDP), among others. The FDA granted Priority Review for the gMG application in Q4 2024, leading to the April 2025 approval.

The PDUFA action date for the wAIHA sBLA has not been disclosed. Given the FDA’s approximately six-month Priority Review timeline, a decision could fall in late 2026, though the agency has not publicly confirmed the target date.