PB0605 - Real World Data on Safety and Efficacy of Emicizumab in Previously Untreated and Minimally Treated Patients under 18 months

Background: The introduction of emicizumab has revolutionised the treatment approach for patients with severe haemophilia A (SHA). Data on emicizumab prophylaxis in previously untreated patients (PUPs) and minimally treated patients (MTPs) infants is scarce.

Aims: The aim of the study was to investigate the safety and efficacy of emicizumab in PUPs and MTPs.

Methods: All patients ≤18 months old who started emicizumab and were either MTPs with ≤5 exposure days or PUPs were included. Data was collected from patients' medical records, Haemtrack system and caregivers questionnaire.

Results: 16 patients were included. Inhibitor screen was negative for the 16 patients prior to starting emicizumab. Median age of starting emicizumab was 8.2 months (range 4.1-15.6) months. 15 out of the 16 were ≤12 months old. Median treatment duration was 61.6 weeks (range 15.3–164.4 weeks). Out of the 16 participants, 10 received emicizumab for over 52 weeks. Before starting emicizumab prophylaxis, 6 patients had minimal treatment, and 10 were PUPs. No major bleeding events were reported. 13 patients had no bleeding events. 5 received Factor VIII (FVIII) treatment, with 3 of these patients requiring FVIII for minor traumatic mouth bleeds, while 2 received FVIII following head trauma. Notably, no bleeding was observed upon head scanning in the latter group. Additionally, two patients received tranexamic acid treatment after minor lip injuries. None of the participant had≥3 treated bleeds. Emicizumab levels for the16 patients were maintained within target ranges with mean trough levels 54 µg/mL.

In terms of safety, no injection site reactions occurred in the patients’ cohort. There were no thromboembolic, or thrombotic microangiopathic events. No other adverse events. No patients acquired new inhibitors during the study period.

Conclusion(s): The study demonstrated that emicizumab was safe and effective in a cohort of 16 infants with SHA who were PUPs or MTPs. Further studies evaluating long term.