OC 73.5 - Efficacy and Safety of Prophylaxis with a Plasma-derived von Willebrand Factor/Factor VIII Concentrate in Type 3 Patients with von Willebrand Disease – A Sub-Analysis of Data from the WIL-31 Study

Background: The WIL-31 study (NCT04052698) demonstrated the efficacy and safety of regular prophylaxis with a plasma-derived von Willebrand factor/factor VIII concentrate (pdVWF/FVIII; wilate®) in people with von Willebrand disease (VWD).

Aims: To analyse the impact of pdVWF/FVIII in a subgroup of WIL-31 patients with type 3 VWD.

Methods: WIL-31 was a prospective, non-controlled, international phase 3 trial that enrolled 33 male/female patients aged ≥6 years with VWD type 1 (VWF:RCo < 30 IU/dL), 2 (except 2N) or 3. Prior to entering the study, patients had received on-demand treatment with any pdVWF/FVIII concentrate during a 6-month, prospective, observational, run-in study. Patients in WIL-31 received prophylaxis with 20–40 IU/kg pdVWF/FVIII 2–3 times per week for 12 months. The primary endpoint was >50% reduction in mean total annualised bleeding rate (ABR) during prophylaxis compared with on-demand treatment. In this post-hoc analysis, type 3 VWD patients were analysed, and further grouped by age: children (6–11 years), adolescents (12–16 years) and adults (≥17 years).

Results: Twenty-two type 3 VWD patients were included in the analysis population, with a median (range) age of 24 (7–61) years. The median weekly prophylactic dose was 62 IU/kg, administered twice weekly in 77% of patients. The mean total ABRs during prophylaxis were 3.9, 5.2 and 6.9 in children, adolescents and adults, respectively, vs 33.4, 32.0 and 40.0 during on-demand treatment, representing 88%, 84% and 86% reductions (Figure 1). The mean spontaneous ABRs during prophylaxis were 2.0, 1.0 and 3.7, respectively. During prophylaxis, 113 bleeds occurred, the vast majority (95%) of which were minor. 41% and 30% were nose and oral bleeds. No serious adverse events related to study treatment and no thrombotic events were observed.

Conclusion(s): Prophylaxis with pdVWF/FVIII was effective and well tolerated in people with type 3 VWD in all age groups.