FDA Priority Review Advances Nipocalimab for Adults With Warm Autoimmune Hemolytic Anemia

FDA has granted priority review to the supplemental biologics license application for nipocalimab-aahu (Imaavy), a neonatal Fc receptor (FcRn)-blocking monoclonal antibody by Johnson & Johnson, in adults with warm autoimmune hemolytic anemia (wAIHA). wAIHA is a rare hemolytic disorder with no FDA-approved therapies.^1,2 The designation sets a shortened review clock of about 6 months and marks the first reported priority review for this indication, Johnson & Johnson announced on April 27, 2026.¹

The decision is clinically notable because treatment for wAIHA remains largely empirical, typically relying on corticosteroids, rituximab, and other immunosuppressive approaches used off-label despite limited prospective data and substantial toxicity concerns.^2,3

“Warm autoimmune hemolytic anemia is a severe disease in which pathogenic immunoglobulin G (IgG) antibodies, also called autoantibodies, drive destruction of red blood cells,” said Leonard L. Dragone, MD, PhD, disease area leader for autoantibody and rheumatology at Johnson & Johnson, in a company press release.¹

What do phase 2/3 trial data suggest about nipocalimab efficacy and safety?

Nipocalimab is intended to reduce circulating IgG, including pathogenic autoantibodies implicated in wAIHA.^1,4 That mechanism is biologically relevant in a disorder defined by warm-reactive IgG autoantibodies that promote erythrocyte destruction, usually through splenic macrophage clearance and, in some cases, complement involvement.^2,3 By lowering IgG rather than broadly suppressing lymphocytes, FcRn inhibition represents a more targeted strategy than conventional steroid-based therapy, although comparative clinical data against active treatment regimens are not yet available.

The application is supported by a phase 2/3 trial (ENERGY), a multicenter, randomized, double-blind, placebo-controlled study followed by an open-label extension in adults with wAIHA.^1,4 According to the company, nipocalimab produced a higher rate of durable hemoglobin response than placebo and also improved fatigue as measured by the Functional Assessment of Chronic Illness Therapy-Fatigue scale.¹ The company defined durable hemoglobin response as hemoglobin concentration of at least 10 g/dL with an increase from baseline of at least 2 g/dL for at least 28 days.¹

The company did not disclose numerical efficacy results, effect size, subgroup findings, or detailed adverse-event rates in its announcement. Full trial data will be presented at a future medical meeting, it said.¹ Information has yet to be disclosed, including the magnitude and timing of hemoglobin improvement, steroid-sparing effects, transfusion outcomes, response durability after treatment interruption, and performance in primary versus secondary wAIHA.

Could nipocalimab become the first FDA-approved therapy for wAIHA?

wAIHA is uncommon but can be clinically severe. Incidence has been estimated at roughly 1 to 3 cases per 100,000 persons annually, and complications can include venous thromboembolism, infection, and organ dysfunction related to severe anemia or treatment exposure.^1-3 Standard first-line therapy is usually corticosteroids, but relapse is frequent, and many patients require rituximab, splenectomy, or steroid-sparing immunosuppressants.^2,3

Recent reviews have highlighted a growing late-stage pipeline in wAIHA, including FcRn antagonists, complement-directed agents, and cellular targets, reflecting both the disease burden and the lack of approved options.³

Nipocalimab already has an FDA-approved indication outside hematology. The drug is approved in the United States for generalized myasthenia gravis in adults and in pediatric patients aged 12 years and older who are anti–acetylcholine receptor or anti–muscle-specific tyrosine kinase antibody positive, according to the current prescribing information cited in the company press release.¹

Safety information in the release for the approved product lists infections, hypersensitivity reactions, infusion-related reactions, respiratory tract infection, peripheral edema, and muscle spasms among the key risks or common adverse effects.¹ Whether the safety profile in wAIHA will mirror that seen in generalized myasthenia gravis is not yet clear, particularly in a population that may have received prior immunosuppression and may carry baseline infection and thrombotic risks.

What is the clinical significance of priority review for nipocalimab in wAIHA?

The regulatory path also reflects broader FDA interest in therapies for rare immune-mediated disease. Priority review does not imply approval, but it indicates the agency considers the application potentially significant for a serious condition.²

If approved, nipocalimab could become the first FDA-approved therapy specifically labeled for wAIHA, a meaningful milestone in a field for which treatment remains largely extrapolated from retrospective studies and expert practice.^2,3 The upcoming FDA action date and eventual label, if approval is granted, would clarify the indicated population, dosing, and monitoring requirements.

References

1. Johnson & Johnson. FDA grants Priority Review for IMAAVY (nipocalimab-aahu) as the potential first approved treatment for people living with warm autoimmune hemolytic anemia (wAIHA). Published April 27, 2026. Accessed April 27, 2026. https://www.jnj.com/media-center/press-releases/fda-grants-priority-review-for-imaavy-nipocalimab-aahu-as-the-potential-first-approved-treatment-for-people-living-with-warm-autoimmune-hemolytic-anemia-waiha
2. FDA. Priority Review. Accessed April 27, 2026. https://www.fda.gov/patients/fast-track-breakthrough-therapy-accelerated-approval-priority-review/priority-review
3. Fattizzo B, Barcellini W. New therapies for the treatment of warm autoimmune hemolytic anemia. Transfus Med Rev. 2022;36(4):175-180. doi:10.1016/j.tmrv.2022.08.001
4. Efficacy and safety of M281 in adults with warm autoimmune hemolytic anemia (ENERGY). ClinicalTrials.gov identifier: NCT04119050. Updated April 13, 2026. Accessed April 27, 2026. https://www.clinicaltrials.gov/study/NCT04119050