Beyond Standard Half-Life: Real-world Pharmacokinetics of Efanesoctocog Alfa in a Single Centre

Efanesoctocog alfa (EFA) is an ultra-extended half-life factor VIII (FVIII) developed to address limitations of conventional prophylaxis in haemophilia A. Although the XTEND trials reported low interindividual pharmacokinetic (PK) variability, real-world data remain important to better characterize PK profiles across patient subgroups.

To report real-world PK data for EFA.

In this single-centre study, adults and children (>6 years) with severe haemophilia A at Strasbourg University Hospital switched from a prior FVIII product to EFA. A simplified PK assessment was performed once or twice per patient after a 50 IU/kg infusion. FVIII activity was measured pre-infusion and at 3, 24, 96 h, and 7 days post-infusion. Patients were reassessed at steady state after ≥6 weeks.

In adults, mean (range) half-life was 52 h (35-62). Mean incremental recovery at 3 h was 2.98 IU/dL per IU/kg (1.85-3.82). Mean FVIII trough levels were 17 IU/dL (5-27) at switch and 19 IU/dL (10-27) at steady state. Significant interindividual variability was observed. Half-life correlated positively with VWF:Ag levels (r = 0.63; p < 0.05) and body weight (r = 0.62; p < 0.05). In children, mean half-life was 53 h (48-59), mean recovery 2.05 IU/dL per IU/kg (1.86-2.26), and trough levels 13-14 IU/dL.

PK profiles matched or exceeded those reported in the XTEND studies, with a slightly longer half-life and higher trough FVIII levels. Notable interindividual variability highlights the value of PK assessments, even for ultra-extended half-life FVIII, to optimize individualized patient management.