CO-44 | EVALUATION OF THE DEVIATION BETWEEN PRESCRIBED AND RECOMMENDED EMICIZUMAB DOSING IN PATIENTS WITH CONGENITAL HEMOPHILIA A

A.C. Giuffrida¹, S. Abeysinghe Gunawardhana¹, S. Amato², F. Casoli², C. Recchi², M. Saggioro², E. Bonetti³, M. Bodini¹, G. Poli² | ¹Centro Emofilia, UOC Medicina Trasfusionale, AOUI Verona, Italy; ²UOC Laboratorio Analisi, AOUI Verona, Italy; ³UOC Oncoematologia Pediatrica, AOUI Verona, Italy

Background. Emicizumab, the first non-replacement therapy approved for the treatment of HA, has significantly improved patient management. However, the label-recommended dosing schedule is highly rigid and, if strictly applied, may lead to unavoidable drug wastage and increased healthcare costs. We analyzed the experience of a single center to assess whether patients received the exact dosage specified in the prescribing information and, in case of deviation, to evaluate the potential impact on clinical outcomes through the analysis of plasma levels of emicizumab.
Patients and Methods. We conducted a retrospective observational study of patients receiving emicizumab prophylaxis at the Hospital of Verona, Italy. Laboratory data, including activated partial thromboplastin time (aPTT), factor VIII (FVIII) activity, plasma emicizumab concentrations, and the occurrence of spontaneous bleeding episodes, were collected between May 2023 and September 2025.
Results. The emicizumab prophylaxis regimens adopted were 1.5 mg/kg once weekly (QW), 3 mg/kg every two weeks (Q2W), and 6 mg/kg once monthly (Q4W). A total of 24 plasma samples were analyzed. Only one patient received the exact label-recommended dose; all other patients were treated with slightly lower doses (mean deviation: 8.13%; range: 3-16.6%). The aPTT ratio ranged from 0.62 to 0.9 (mean of 0.74). Plasma emicizumab concentrations ranged from 16.5 µg/mL to 90.3 µg/mL (mean: 48 µg/mL). Mean plasma emicizumab concentrations per patient ranged from 25.80 µg/mL to 86.43 µg/mL. According to the dosing schedule, mean plasma emicizumab concentrations were 40.56 µg/mL for the 1.5 mg/kg QW regimen, 65.02 µg/mL for the 3 mg/kg Q2W regimen, and 31.51 µg/mL for the 6 mg/kg Q4W regimen. No spontaneous bleeding episodes were observed in any patient. Based on our calculations, strict adherence to the label-recommended dose would have resulted in the disposal of approximately 5 to 18 mg of emicizumab per administration per patient. On an annual basis, this would correspond to a total of 2,922.72 mg of discarded drug, equivalent to approximately 20 vials of 150 mg/mL formulation.
Conclusions. Despite the limited number of patients and samples analyzed, our findings show that most patients received a slightly lower dose of emicizumab than the label-recommended without compromising treatment efficacy or safety. Plasma emicizumab concentrations were generally within the therapeutic range, and no spontaneous bleeding events were reported. These small deviations from the recommended dosing regimen allowed for a substantial reduction in drug wastage while maintaining effective prophylaxis.