Emicizumab for Severe VON Willebrand Disease (VWD) and VWD/Hemophilia A

Von Willebrand Disease (VWD) is the most common inherited bleeding disorder affecting up to 0.1% of the population, is usually characterized by mucocutaneous bleeding, HMB, surgical bleeding or other hemostatic challenges. VWD currently has few therapies generally useful in management of bleeding events including antifibrinolytics, desmopressin (DDAVP), and VWF concentrates, which may be plasma-derived (VWF with and without FVIII) or recombinant. Minor bleeding may be successfully treated with antifibrinolytics and DDAVP; however, more severe bleeding requires VWF concentrates that are administered solely through intravenous access.

Similarly, it can be challenging to treat concomitant bleeding disorders with the existing therapeutic options available, and patients with concurrent VWD and hemophilia A primarily have VWF/FVIII concentrate or desmopressin (DDAVP) available for treatment. It has been well-recognized that patients, caregivers, and medical providers desire additional, simplified therapeutic options that are not intravenous to treat severe bleeding disorders. Therefore, a simplified, subcutaneous therapeutic that prevents bleeding would be strongly desired. Though its use in the hemophilia A population is growing, additional potential emicizumab applications for hemostatic control in other hemostatic disorders remain unknown. A recent case report highlighted the hemostatic efficacy of emicizumab off-label use in type 3 von Willebrand Disease (VWD), another severe bleeding disorder. This pediatric patient had type 3 VWD with alloantibodies and a bleeding phenotype similar to hemophilia A with inhibitor patients, requiring suboptimal bleeding management with rFVIIa and activated prothrombin complex concentrates (aPCC). Emicizumab prophylaxis was initiated and the patient no longer required aPCC prophylaxis and rare use of rFVIIa for acute bleeding events (only 1 trauma-induced soft tissue hematoma at the time of publication). The authors concluded their report suggested the bleeding phenotype in type 3 VWD is expressed mainly due to factor VIII deficiency. This study suggests a potential additional application for emicizumab in severe VWD.

A pilot multicenter, prospective open-label study of emicizumab prophylaxis in severe VWD and concomitant VWD/hemophilia A. Patients will have a one-year retrospective chart review of annualized bleed rate and hemostatic therapies collected at the time of enrollment. Patients will then be treated with emicizumab with 3mg/kg weekly for 4 weeks loading dose, followed by once weekly prophylaxis of 1.5mg/kg for 1 year. Per emicizumab FDA-approved prescribing information for hemophilia A, dose up-titration to 3 mg/kg once weekly will be allowed after 24 weeks on HEMLIBRA prophylaxis in case of suboptimal efficacy (i.e., ≥ 2 spontaneous and clinically significant bleeds) Treatment records will be maintained along with bleeding event logs. Breakthrough bleeding events may be treated with the patients usual on-demand therapy with antifibrinolytics or VWF/FVIII concentrates per clinician discretion. Patient reported outcome assessments will be collected throughout the clinical study to collect impact of the treatment on the individual patients, assessing quality of life, physical, emotional, social and general symptoms.