Efanesoctocog alfa for hemophilia A: results from a phase 1 repeat-dose study

Abstract

Efanesoctocog alfa (rFVIIIFc-VWF-XTEN, BIVV001) is a new class of factor VIII (FVIII) replacement that breaks the von Willebrand factor-imposed FVIII half-life ceiling. In a Phase 1/2a study, single-dose efanesoctocog alfa was well tolerated and no safety concerns were identified. We evaluated the safety, tolerability, and pharmacokinetics of repeat-dose efanesoctocog alfa in a Phase 1 study in previously treated adults (≥150 exposure days) with severe hemophilia A. Participants received four once-weekly efanesoctocog alfa doses (Cohort 1, 50 IU/kg; Cohort 2, 65 IU/kg). All enrolled participants (Cohort 1, n=10; Cohort 2, n=14) completed the study. Inhibitor development to FVIII was not detected. After the last efanesoctocog alfa dose, geometric mean (range) FVIII activity half-life, area under the activity-time curve, and steady state maximum concentration for Cohort 1 and Cohort 2 were 41.3 (34.2-50.1) hours and 37.3 (28.9-43.8) hours, 8290 (5810-10,300) h × IU/dL and 11,200 (7040-15,800) h × IU/dL, and 131 (96-191) IU/dL and 171 (118-211) IU/dL, respectively. There was minimal accumulation after 4 doses. Mean FVIII activity on Day 3 post dose was 46% and 69% and on Day 7 was 10% and 12% for Cohorts 1 and 2, respectively. Overall, four once-weekly doses of efanesoctocog alfa were well tolerated, no safety concerns identified, and no bleeds reported during the treatment period. Once-weekly efanesoctocog alfa provided high sustained FVIII activity within the normal to near-normal range for 3-4 days post-dose and may improve protection against bleeds in patients with hemophilia A. (EU Clinical Trials Register study 2018-001535-51)