Factor VIII and von Willebrand factor activity levels during long-term prophylaxis with wilate-Analyses from the WIL-31 study.

BACKGROUND

Long-term von Willebrand factor (VWF) prophylaxis is recommended for people with von Willebrand disease (VWD) who experience frequent and severe bleeds. However, repeated administration of VWF-containing concentrates may lead to VWF and/or factor (F)VIII accumulation, with an increased thrombotic risk. Data on FVIII and VWF accumulation during prophylaxis in VWD are lacking.

OBJECTIVES

This study analyzed FVIII and VWF activity levels during long-term prophylaxis with wilate, a plasma-derived VWF/FVIII concentrate containing VWF and FVIII in a physiological 1:1 activity ratio, in the prospective WIL-31 study.

METHODS

Preinjection and postinjection FVIII and VWF activity levels were measured in plasma at baseline and after 1, 2, 3, 6, 9, and 12 months of wilate in the 33 patients who completed WIL-31. Analyses were descriptive and included stratification by age and VWD type.

RESULTS

VWF and FVIII activity levels (IU/dL) remained stable during 12 months of prophylaxis. Mean (SD) VWF activity levels preinjection and postinjection were 6.7 (4.0) and 59.0 (28.7) at baseline and 8.6 (7.6) and 44.4 (20.5) at 12 months, respectively. For FVIII, levels were 13.2 (18.9) and 75.5 (31.3) at baseline and 27.5 (25.6) and 83.6 (30.0) at 12 months, respectively. Similarly, when stratified by age and VWD type, no accumulation of either factor was observed. No thrombotic events were reported.

CONCLUSIONS

During 12 months of wilate prophylaxis, there was no accumulation of FVIII or VWF regardless of age and VWD type, and no thrombotic events were reported. These findings from WIL-31 confirm and extend wilate's existing safety data.