Spanish registry of real-world clinical practice in previously untreated or minimally treated patients with severe hemophilia A (RePUM-HA)

Introduction: The development of inhibitors against factor VIII remains a significant complication in hemophilia A, especially in previously untreated patients. Non-replacement therapies have enabled the initiation of primary prophylaxis at very early stages, although uncertainties persist regarding the risk of inhibitor development after late factor VIII exposure, the choice of concentrate, and tolerization strategies. Objective: The aim of the RePUM-HA registry is to generate real-world evidence to better understand and reach consensus on the management of these patients in our country. Material and method: National, multicenter, observational registry running from 2021 to 2028, including previously untreated and minimally treated patients (< 5 exposure days) with severe or moderate hemophilia A, under 3 years of age, without inhibitors, who started prophylaxis after 2020. Clinical, genetic, therapeutic, bleeding, immunogenicity, and adverse event data will be collected. Results: Approximately 50 patients are expected to be enrolled to assess inhibitor risk, clinical outcomes, and prophylactic regimens in real-world practice. Conclusions: This study will provide evidence to optimize strategies and inform future national recommendations.