What's New and What's Next for Emicizumab for the Treatment of Hemophilia A?
Mahlangu Johnny N JN
Emicizumab, a bispecific factor VIIIa-mimetic antibody, has transformed hemophilia A prophylaxis by providing an effective subcutaneous treatment regardless of factor VIII inhibitor status. The HAVEN program established sustained reductions in treated bleeding, favorable safety, and reduced treatment burden across children and adults. More recent evidence has expanded its use into infancy, previously untreated patients, and selected people with moderate or mild hemophilia A, shifting treatment toward prevention before recurrent bleeding and joint damage occur. Real-world experience broadly confirms the trial's efficacy but also highlights important limitations. Zero treated bleeds does not necessarily indicate absence of pain, synovitis, or progressive arthropathy. At the same time, breakthrough bleeding, laboratory assay interference, rare neutralizing anti-drug antibodies, and thrombotic complications associated principally with excessive activated prothrombin complex concentrate remain clinically relevant. Emicizumab controls bleeding in patients with factor VIII inhibitors but does not induce immune tolerance, leaving unresolved questions regarding inhibitor eradication, delayed factor VIII exposure, and optimal induction of immune tolerance. The next phase of development will require moving beyond uniform weight-based dosing and annualized bleeding rates toward individualized exposure, validated biomarkers, and outcomes that encompass joint structure, physical participation, quality of life, and treatment burden. Emicizumab must also be positioned against next-generation factor VIII mimetics, rebalancing therapies, sustained-exposure factor VIII replacement, and gene therapy. This review critically examines the established and emerging evidence, practical management challenges, unresolved scientific questions, and future therapeutic positioning of emicizumab. Its ultimate impact will depend not only on broader eligibility, but also on precision use, long-term safety, rational treatment sequencing, and equitable global access.