Type 3 Von Willebrand International Registries Inhibitor Prospective Study

Von Willebrand's Disease (VWD) is the most common inherited bleeding disorder, characterized by a quantitative and/or qualitative deficiency of Von Willebrand Factor (VWF), that plays a major role in early phases of hemostasis. Type 3 Von Willebrand's Disease (VWD3) is due to virtually complete deficiency of VWF and, for this reason, has been also described as "severe VWD". Recurrent Gastro-Intestinal Bleeds (GIB) is one of the most challenging complications encountered in the management of patients with VWD. The commonest cause is angiodysplasia (ANGDYS), but often no cause is identified due to the difficulty in making the diagnosis. In recent years, research from several laboratories has identified multiple roles for VWF in the control of vascular function. Globally, these findings provide the first possible explanation for the presence of ANGDYS in patients with VWD. These vascular malformations in the gastrointestinal (GI) tract are characterized by fragile, leaky mucosal vessels. Combined with the hemostatic dysfunction, these can lead to severe intractable bleeding including GIB. VWD3 is inherited as a recessive trait and heterozygous relatives have mild or no bleeding symptoms. Even if the prevalence of VWD3 is very low, the highest rate is found in Iran and the lowest in southern Europe. However, the actual prevalence of VWD3 is still unknown in most countries, due to the lack of retrospective or prospective studies. Although rare, VWD3 is of major interest because of its severe clinical presentation, the need for replacement therapy with plasma-derived and/or recombinant VWF concentrates and the risk of occurrence of anti-VWF inhibitors after the infusion of VWF concentrates, for which risk factors have not been systematically determined.

The major objectives of the study are: to create an international network among European and Iranian Centers (ratio 1:1), the prospective enrollment of at least 250 VWD3 patients using a common database online, the collection of detailed information about previous bleedings and exposure to plasma-derived and/or recombinant VWF concentrates, the use of bleeding severity score of VWD3 calculated with a common questionnaire, the collection of plasma and DNA samples from all the identified VWD3 patients enrolled for centralized analyses, the confirmation of the local VWD3 diagnosis using centralized tests, Evaluation of VWF gene defects, VWF phenotype and risk of anti-VWF inhibitors through common methods, the evaluation of potential correlations between phenotypic results (including markers of angiogenesis) and GIB occurrence, the objective evaluation of severity of GIB in VWD3 patients, the assessment of frequency and sites of bleeding in VWD3 patients followed-up for 2 prospective observation periods (2 years each: 2017-2018 and 2020-2022), the efficacy assessment of the plasma-derived and/or recombinant VWF concentrates used to treat VWD3 (on demand versus prophylaxis) using the most objective criteria for efficacy during 2 prospective observation periods (2 years each: 2017-2018 and 2020-2022), the evaluation of the efficacy and safety of plasma-derived and/or recombinant VWF concentrates in the treatment of GIB during 2 prospective observation periods (2 years each: 2017-2018 and 2020-2022), in comparison to the use of anti-angiogenetic agents within the standard clinical setting.

To these purposes, a cohort of at least 250 patients with diagnosis of VWD3 will be enrolled using homogenous and standardized criteria.

The work planned to achieve the objectives of the project will be divided in three parts:

• the first part deals with standardized criteria for enrolment and collection of retrospective clinical and laboratory data, to be confirmed by centralized laboratories;
• the second part involves a further characterization of clinical and laboratory parameters, collected in the retrospective phase, including prevalence of anti-VWF inhibitors, advanced laboratory tests to further identify VWD3, mutations analyses of the VWF gene;
• the third part of the study is divided in two parts: a first prospective observation and a second prospective observation. The third part for the first time deals with the prospective clinical observation in a large cohort of VWD3 patients all previously well characterized by an international panel of experts.

Inclusion criteria

• Male and female of any age, including infants, children, adolescent and adults
• Informed Consent obtained (parents should sign for patients < 18 y.o.)
• Previous Diagnosis of VWD3 (VWF Antigen: undetectable or <5 U/dL)
• Detailed information on inherited pattern, history of bleeding, previous exposure to blood products
• Availability of plasma and DNA samples

Exclusion criteria

• VWD3 patients who may not be available for follow-up