BT200 in Hereditary Bleeding Disorders

BT200 is a PEGylated aptamer that binds to the A1 domain of human von Willebrand factor (VWF). At low doses, BT200 blocks the clearance of VWF antigen (VWF Ag) from the circulation and causes an increase in concentrations of both VWF Ag and Factor VIII (FVIII), but has negligible effect on the activity of either. At higher doses, BT200 blocks clearance of VWF and also inhibits its activity, but still does not inhibit FVIII activity. Therefore, low dose BT200 could potentially be used to correct deficiency of VWF and/or FVIII in patients with hereditary bleeding disorders. This study is designed as a "basket design" pilot study to determine the relevant dose and pharmacological activity of BT200 in such patients. In this open basket study up to 25 patients with the following congenital blood-clotting disorders are to be included: Patients with hemophilia A, heterozygous carriers of hemophilia A with subnormal FVIII levels; patients with von Willebrand syndrome (VWD) type 1, "Vicenza type", and with VWD type 2b. Participants will receive BT200 subcutaneously on day 0, day 4 and day 7 in the first week and then once a week for a total of five weeks - initially in a dose of 3 mg, then in week 3 individually after response in a dose of 3 to 9 mg. Subsequently, blood samples are taken once a week for a further three weeks (wash-out phase). Patients may be enrolled in an additional pharmacokinetics sub-study. For this purpose, approximately three blood samples are taken to estimate the half-life of substituted FVIII under the influence of BT200. The primary objective of this study is to obtain clinical proof of mechanism for BT200 in one or more hereditary bleeding disorders.