Intraindividual bleeding outcomes in patients with hemophilia A on emicizumab prophylaxis in Australia

Emicizumab became routinely available in Australia in November 2020 as regular prophylaxis for certain patients with hemophilia A (HA). We performed an intraindividual comparison of bleeding outcomes in Australian patients with HA before and after commencement of emicizumab. Data regarding demographics, severity, treatment, inhibitors, and number and type of intraindividual treated bleeds before and after starting emicizumab in patients with HA were extracted from the Australian Bleeding Disorders Registry. As of April 2022, there were 459 eligible patients with HA on emicizumab in Australia, 397 of 459 (86%) of whom had severe disease. Overall, 59 of 459 (13%) had a current inhibitor. Adults (aged ≥18 years) composed 49% (223/459) of the population. The proportion of patients with zero bleeds increased from 54% to 63% after commencement of emicizumab (relative risk [RR], 1.24; 95% confidence interval [CI], 1.09-1.41; P < .01). RR for zero treated bleeds after commencement was significant in subgroups including pediatric patients (RR, 1.34; 95% CI, 1.13-1.59; P < .01) and those not on regular prophylaxis prior (RR, 1.75; 95% CI, 1.22-2.52; P < .01). There was no significant difference in zero-bleed prevalence in the adult, standard half-life, and extended half-life subgroups. Spontaneous bleeding was reduced (RR, 1.69; 95% CI, 1.34-2.13; P < .01), whereas provoked bleeding was not (P = .15). Real-world data from Australia shows a reduction in bleeding events with emicizumab prophylaxis for the overall population of patients with HA, although not in all subgroups. This reduction appears to be most pronounced in spontaneous bleeds within the pediatric population, and in those on on-demand therapy before switching.