Treatment of von Willebrand disease with a high-purity factor VIII/von Willebrand factor concentrate: a prospective, multicenter study

Among patients with von Willebrand disease (VWD) who are unresponsive to desmopressin therapy, replacement with plasma-derived concentrates is the treatment of choice. Because prospective studies are lacking, such treatment has been largely empirical. A multicenter, prospective study has been conducted in 81 patients with VWD (15 patients with type 1, 34 with type 2, and 32 with type 3 disease) to investigate the efficacy of a high-purity factor VIII/von Willebrand factor (FVIII/VWF) concentrate for treatment of bleeding and surgical prophylaxis. Two preparations of the concentrate-one virally inactivated with solvent detergent, the other with an additional heat-treatment step--were evaluated. Pharmacokinetic parameters were similar for both preparations. Using pre-established dosages based on the results of pharmacokinetic studies, 53 patients were administered either preparation for the treatment of 87 bleeding episodes, and 39 patients were treated prophylactically for 71 surgical or invasive procedures. Sixty-five (74.7%) and 10 (11.5%) of the bleeding episodes were controlled with 1 or 2 infusions, respectively. Patients with severe type 3 VWD typically required more infusions and higher doses, at shorter time intervals, than did patients with generally milder types 1 and 2. Among patients undergoing surgical procedures, blood loss was lower than that predicted prospectively, and losses exceeding the predicted value did not correlate with the postinfusion skin bleeding time. In conclusion, the concentrate effectively stopped active bleeding and provided adequate hemostasis for surgical or invasive procedures, even in the absence of bleeding time correction

Three-dimensional structure of fibrolase, the fibrinolytic enzyme from southern copperhead venom, modeled from the x-ray structure of adamalysin II and atrolysin C

The fibrinolytic enzyme from southern copperhead snake venom, fibrolase, contains 1 mole of zine per mole of protein, belongs to the major family of metalloproteinases known as the metzincins, and has been shown to degrade fibrin clots in vitro and in vivo. The purpose of this study was to develop a 3-dimensional model of fibrolase to investigate the geometry of conserved and variable sequences between members of the snake venom metalloproteinases. When compared to atrolysin C (form D) or adamalysin II (metzincins with completely different substrate specificity), fibrolase has approximately 60% overall sequence identity and nearly 100% sequence similarity in the active site. We used the crystal structure of adamalysin II to build a 3-dimensional homology model of fibrolase. Three disulfide bonds were constructed (the highly conserved disulfide bond [118–198] was maintained from the adamalysin II structure and 2 new disulfide bonds were introduced between residues 158–182 and 160–165). We used Sculpt 2.5 and HyperChem 5.0 to “dock” a substrate fragment octapeptide (HTEKLVTS), and a water molecule into the active site cleft. We calculated the differential average homology profile for fibrolase compared to 8 hemorrhagic and 5 nonhemorrhagic metzincins. We then determined the sequence regions that might be responsible for their substrate specificity. Our 3-dimensional homology model shows that the variable sequences lie on the periphery of the identified active site region containing the His triangle; this indicates that substrate specificity may depend on surface residues that are not directly associated with the active site