Interim Canadian Data from a Prospective, Observational Study of Routine Clinical Use of a Von Willebrand Factor Concentrate (Wilate®)

Introduction:Von Willebrand disease (VWD) is the most common congenital bleeding disorder with a prevalence of symptomatic cases of 1 in 1,000. VWD is characterized by quantitative or qualitative abnormalities in von Willebrand factor (VWF), resulting in impaired haemostasis. To increase VWF levels, VWF concentrates are the only treatment option for approximately 20% of VWD patients for whom 1-deamino-8-D-arginine vasopressin (DDAVP) is not effective or is contraindicated. Wilate® (Octapharma AG, Lachen, Switzerland) is a high purity, double virus-inactivated, freeze-dried concentrate of VWF and FVIII. The ratio of VWF to FVIII is near the physiological value of 1:1 and is designed to simplify dosing and monitoring. Wilate®, initially approved in 2005 in Germany, is currently broadly approved worldwide for treatment of VWD and Hemophilia A. This non-interventional, prospective study in VWD patients was designed to collect information on the safety, tolerability and efficacy of Wilate® in routine clinical practice. We present the results of an interim analysis conducted in Canadian patients who received Wilate® in a routine clinical setting as prophylaxis, on-demand treatment and/or in a surgical setting.

Methods:Ethics committee approval was obtained from all participating centres, and all VWD patients prescribed Wilate® from participating physicians were eligible for inclusion. Patients were excluded for the presence of VWF inhibitors, bleeding disorders other than VWD, a history of non-compliance, prohibitively difficult venous access, or the inability to follow study requirements. Routine clinical use of Wilate® for prophylaxis, on demand treatment of bleeding episodes, and prophylaxis for major and minor surgeries were documented. Parameters of routine clinical use are reported here and include exposure days, dosing, and number of infusions. Adverse drug reactions (ADRs), tolerability assessments, and haemostatic efficacy assessments are also reported.

Results:Interim data from 13 patients, with a mean age of 45.6 (range 16 to 78 years), enrolled in participating Canadian centres was available for this analysis. Patients consisted of 3 males and 10 females, nine with type 1, three with type 2, and one with type 3 VWD. Two patients were treated for on-demand bleeding episodes, 2 were treated prophylactically, whereas 11 patients were treated for surgeries. A total of 1 051 000 IU Wilate® was infused in the thirteen patients with an average dose for all indications of 46 ± 9.7 IU/kg. Tolerability was 'excellent' in 284 of 285 (99.6%) assessed infusions. Hemostatic efficacy of Wilate® was assessed as 'excellent' or 'good' for all on-demand treatments of bleeding episodes. All 29 breakthrough bleeds, which were primarily GI bleeding, were treated successfully in one long-term prophylactic patient with severe VWD in 17 months. One other patient was treated for seventeen days following surgery and experienced no bleeding episodes. Eleven patients underwent 12 surgical procedures, one patient underwent 2 minor dental procedures, and 10 patients underwent ten major surgeries. In all 12 surgeries the haemostatic efficacy of Wilate® treatment was assessed as 'excellent.' No thrombotic events or severe ADRs were observed.

Conclusion:This study is a part of ongoing pharmacovigilance of Wilate® and these interim observations support its safety and efficacy for VWD patients in routine clinical settings. In our Canadian cohort, under routine clinical conditions, bleed resolution, prevention, and tolerability were high.