Real-world use of emicizumab in Chinese children with hemophilia A: Retrospective data from a comprehensive care center.

Importance: Emicizumab (EMI) is efficacious and safe for hemophilia A (HA) prophylaxis. However, its high cost poses a challenge in China. Objective: To explore the possibility of using reduced-dosage EMI in Chinese HA children. Methods: We conducted a retrospective study for HA children in our Comprehensive Care Center. Data were collected pre- and post-EMI treatment to evaluate bleeding rates. Laboratory analyses included factor VIII (FVIII)-like activity and EMI concentration measurements. Results: Thirty-four HA children receiving EMI prophylaxis for a median (range) 24.5 (2.5-47.9) months by June 2023. Of these, 25 (73.5%) were under 3 years of age, 26 (76.5%) had severe hemophilia and 12 (35.3%) were minimally treated or previously untreated patients. Thirty-one (91.2%) of the 34 patients received reduced-dosage EMI for economic reasons. EMI concentration and FVIII-like activity measured showed a strong correlation. Overall, while on EMI, their annual treated bleeding rate (ATBR) and annual bleeding rate (ABR) decreased significantly (2-0) while their zero-bleeding rate (ZBR) increased significantly (11.5%-65.4%). After 6 months of EMI, there was no significant difference in ATBR and ABR among various maintenance dosages. However, ZBR was significantly lower in dosages under 4 mg/kg ( Interpretation: We showed EMI effectively prevented bleeding even at reduced dosages. However, the bleeding risk may be higher with EMI 4-weekly maintenance dosage <3.8 mg/kg, EMI concentration <48.1 μg/mL, and FVIII-like activity <15.4 IU/dL for zero bleeding. It is important that dosage reduction be done rationally. Dosage tailoring is possible.