Abstract
Abstract 237
Von Willebrand Disease (VWD) is an inherited rare bleeding disorder caused by a deficiency of von Willebrand factor (VWF). VWF is the largest soluble multimeric plasma glycoprotein, which facilitates platelet aggregation and stabilizes FVIII in the circulation. Patients with type 3 disease display severe hemorrhagic symptoms, mainly in mucosal tissues, muscle and joints. Replacement of VWF stabilizes endogenous FVIII to hemostatic levels within hours. Commercially available VWF/FVIII concentrates are plasma-derived (pd) and subject to limitations such as donor dependency, risk of blood-borne pathogen transmission, lack of high molecular weight VWF multimers, and variation in multimer composition. A novel recombinant human VWF (rhVWF) has been developed using a plasma-free method, which represents the largest protein ever produced using recombinant technology. Safety, tolerability and pharmacokinetics of the rhVWF combined at a fixed ratio with rFVIII were investigated in a Phase 1 multicenter, international clinical study in 31 patients with type 3 VWD and severe type 1 VWD. Four concentrations of rhVWF (2, 7.5, 20 and 50 IU VWF:RCo/kg) were administered in a dose-escalating manner in separate cohorts. rhVWF was well tolerated, and no thrombotic events, VWF inhibitors or other serious adverse reactions were observed. Pharmacokinetics of rhVWF/rhFVIII (50 IU VWF:RCo/kg and 38.5 IU FVIII/kg) compared with pdVWF/pdFVIII (50 IU VWF:RCo/kg and 21 IU/kg FVIII/kg) were evaluated in a sub-group of 8/31 patients using a randomized, crossover design (8-day minimum washout period). Interim data in 8 subjects show a higher degree of secondary FVIII activity with rhVWF/rhFVIII compared to pdVWF/pdFVIII (see Figure 1) that is not solely due the difference in the rhVVF:FVIII infusion ratio (1.3:1 rhVWF/rhFVIII vs. approximately 2:1 pdVWF/pdFVIII). The pharmacokinetics of the rhVWF:RCo and pdVWF:RCo were comparable and were also reflected in the VWF:Ag and collagen binding activity. Evidence is also provided for the in vivo cleavage of the ultra-high molecular weight multimers of rhVWF by endogenous ADAMTS13. In summary, interim data from the ongoing Phase 1 study, demonstrate that rhVWF is safe and well tolerated, has VWF:RCo pharmacokinetics that are comparable to pdVWF and enhances stabilization of endogenous FVIII. Multiple doses of rhVWF/rhFVIII would be expected to have beneficial effects in major surgery and severe mucosal bleeding events. These data would also support the treatment concept to administer rhVWF alone once a therapeutic baseline level of endogenous FVIII is achieved (after 1–2 doses).Figure 1:Preliminary PK data from 8 subjects post-infusion of either rhVWF/rhFVIII or pdVWF/pdFVIII. Endogenous FVIII activity reached a plateau after 6 hours and remained stable for at least 30 hours. FVIII was still elevated well above baseline at 96 hoursFigure 1:. Preliminary PK data from 8 subjects post-infusion of either rhVWF/rhFVIII or pdVWF/pdFVIII. Endogenous FVIII activity reached a plateau after 6 hours and remained stable for at least 30 hours. FVIII was still elevated well above baseline at 96 hours
Disclosures:
Suiter: Baxter BioScience: Employment. Laffan:Baxter BioScience: Consultancy. Mannucci:Baxter BioScience: Consultancy. Kempton:Baxter BioScience: Consultancy. Romond:Baxter BioScience: Consultancy. Shapiro: Baxter BioSci- ence: Consultancy. Birschmann:Baxter BioScience: Consultancy. Gill:Baxter BioScience: Consultancy. Ragni:Baxter BioScience: Consultancy. Turecek:Baxter BioScience: Employment. Ewenstein:Baxter Bioscience: Employment. Baxter BioScience:Baxter BioScience: Employment.
Phage Display Broadly Identifies Inhibitor-reactive Regions in von Willebrand Factor