Introduction: Persons with haemophilia A (PwHA) with inhibitors to factor VIII often experience decreased health-related outcomes. In HAVEN 1 (NCT02622321), there was a statistically significant reduction in bleeding with emicizumab prophylaxis versus no prophylaxis. Aim: Describe health-related outcomes in PwHA with inhibitors in HAVEN 1. Methods: PwHA with inhibitors aged 6512\ua0years previously on episodic bypassing agents (BPAs) were randomized to emicizumab prophylaxis (Arm A; n\ua0=\ua035) or no prophylaxis (Arm B; n\ua0=\ua018); participants previously on BPA prophylaxis received emicizumab prophylaxis (Arm C; n\ua0=\ua049). Health-related outcomes assessed at baseline and monthly thereafter: Haemophilia Quality of Life Questionnaire for Adults (Haem-A-QoL), Haemophilia-specific Quality of Life Questionnaire for Children Short Form (Haemo-QoL SF), EuroQol 5-Dimensions 5-Levels (EQ-5D-5L) index utility score (IUS) and visual analogue scale (EQ-VAS) and work/school days. Days hospitalized also recorded. Results: At week 25, differences (ANCOVA) in adjusted mean scores (95% confidence interval) favoured Arm A versus B for Haem-A-QoL \u201cTotal\u201d score (14.0 [5.6, 22.5]; P\ua0=\ua00.002) and \u201cPhysical Health\u201d (21.6 [7.9, 35.2]; P\ua0=\ua00.003); EQ-VAS ( 129.7 [ 1217.6, 121.82]; P\ua0=\ua00.017); and IUS ( 120.16 [ 120.25, 120.07]; P\ua0=\ua00.001); mean scores are comparable in Arms A and C. Throughout the study, a greater proportion of participants on emicizumab prophylaxis than no prophylaxis exceeded questionnaire-specific responder thresholds. Mean proportion of missed work days and number of days hospitalized were lower with emicizumab prophylaxis than no prophylaxis. Conclusions: In PwHA with inhibitors, emicizumab prophylaxis was associated with substantial and meaningful improvements in health-related outcomes
