Bleeding control improves after switching to emicizumab: Real-world experience of 177 children in the PedNet registry

Introduction: Despite the rapid uptake of emicizumab in the paediatric haemophilia A (HA) population, real-world data on the safety and efficacy is limited. Aim: To report on bleeding and safety in paediatric patients receiving emicizumab prophylaxis. Methods: Data were extracted from the multicentre prospective observational PedNet Registry (NCT02979119). Children with haemophilia A, and ≥50 FVIII exposures or inhibitors present receiving emicizumab maintenance therapy were analysed. Data were summarized as medians with interquartile range (IQR, P25–P75). Mean (95% confidence interval (CI)), annualized (joint) bleeding rate (A(J)BR) during emicizumab and ≤2 years before emicizumab prophylaxis were modelled and compared using negative binomial regression. Results: Total of 177 patients started emicizumab at median 8.6 years (IQR 4.8–13.1), most had no FVIII inhibitors (64%). Follow up before emicizumab was median: 1.68 years (IQR: 1.24–1.90) and during emicizumab: 1.32 years (IQR:.94–2.11). In patients without inhibitors, mean ABR reduced after starting emicizumab from 2.41 (CI 1.98–2.95) to 1.11 (CI.90–1.36, p <.001), while AJBR reduced from.74 (CI.56–.98) to.31 (CI.21–.46, p <.001). Concordantly, in patients with inhibitors, mean ABR reduced from 5.08 (CI 4.08–6.38) to.75 (CI.56–1.01, p <.001), while AJBR reduced from 1.90 (CI 1.42–2.58) to.34 (CI.21–.56, p <.001). Five emicizumab-related adverse events were reported (3% of the cohort), including one patient with antidrug antibodies. Conclusion: This study showed improved bleeding control compared to previous treatment and a favourable safety profile during emicizumab therapy in paediatric haemophilia A patients. Trial registration: Clin.gov.trial-NCT02979119.