Transition to Emicizumab from standard-dose FVIII prophylaxis in young children with hemophilia A: a real-world study

BACKGROUND: Real-world evidence on transition from standard-dose FVIII to Emicizumab prophylaxis in young children with hemophilia A remains limited, particularly in developing countries. METHODS: We performed a single-center, retrospective, self-controlled study in boys with severe hemophilia A without inhibitors. Outcomes during 12 months of standard-dose factor VIII (FVIII) prophylaxis were compared with outcomes during 12 months after transition to Emicizumab prophylaxis (in this real-world cohort, most patients received reduced-dose maintenance regimens). Annualized bleeding rates (overall, treated, joint, and spontaneous) and zero-bleeding proportions were assessed. Direct annual prophylaxis drug costs were calculated using locally applicable drug prices and converted to USD. RESULTS: Thirty-one boys were included with a median age of 4.5 years. During FVIII prophylaxis, the median FVIII dose was 32.3 IU/kg/infusion with a median 3.1 infusions/week; median trough FVIII was 3.9 IU/dL. After transition, mean Emicizumab exposure was 4.2 mg/kg/month (range 3.0-6.0) with a mean dosing interval of 14 days. Overall ABR decreased from 2.48 to 0.32, treated ABR from 1.64 to 0.29, joint ABR from 0.83 to 0.13, and spontaneous ABR from 0.26 to 0 (all P < 0.05). The proportion of patients with zero bleeds increased from 35% to 81% (P < 0.001), and zero treated bleeds from 52% to 69% (P < 0.05). Mean annual prophylaxis drug costs were lower with Emicizumab than with FVIII (34,417 vs. 47,168 USD; P < 0.001). CONCLUSIONS: In this selected pediatric cohort of children who transitioned from standard-dose FVIII to Emicizumab and remained on treatment for at least 12 months, lower observed bleeding rates and lower direct prophylaxis drug costs were seen during the Emicizumab period. These findings should be interpreted descriptively because the retrospective design and eligibility criteria introduced substantial selection bias. TRIAL REGISTRATION: Not applicable.