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Bleeding Disorder Drug Has 100% Success Rate in Late-Stage Study

FDA considers therapy for von Willebrand disease

Additional data have been reported from a phase III clinical trial of BAX 111 (Baxter International Inc.), the first highly-purified recombinant von Willebrand factor (rVWF) in clinical development as a treatment for patients with von Willebrand disease (VWD), the most common type of inherited bleeding disorder.

The new findings were presented at the 2015 scientific symposium of the Hemostasis and Thrombosis Research Society (HTRS) in New Orleans, Louisiana. The trial met its primary efficacy endpoint, defined as the number of patients who achieved treatment success for the control of bleeding episodes.

All 22 patients treated in the full analysis set experienced a 100% treatment success rate based on a four-point efficacy rating scale, which compared the estimated number of infusions needed to treat the bleeding episodes with the number of infusions administered.

Efficacy for all treated bleeds (n = 192) was rated “excellent” (96.9%) or “good” (3.1%), including major bleeds (six “excellent” and one “good”). The median number of infusions required to treat bleeding events in the trial was one, and most of the events (81.8%) were resolved with a single infusion.

The open-label study was designed to assess the safety, efficacy, and pharmacokinetic (PK) characteristics of BAX 111 in patients 18 to 65 years of age with severe VWD. Bleeding events that occurred during the study were initially treated with rVWF (40 to 60 IU/kg; up to 80 IU/kg for major bleeds) together with rFVIII and subsequently alone if hemostatic FVIII levels were maintained. rVWF PK parameters were determined with and without rFVIII and were repeated after 6 months for rVWF; these analyses found that the PK characteristics of rVWF were not affected by administration with rFVIII.

According to Baxter, the recombinant technology used to produce BAX 111 avoids certain protein-maturation processes that typically occur with plasma fractionation. This preserves large functional units, known as ultra-large multimers, which have been shown to be efficient in clot formation and FVIII stabilization.

No patients developed inhibitors or binding antibodies to the treatment, and there were no reports of thrombotic events or severe allergic reactions. Eight adverse events (AEs) were considered causally related to BAX 111: six nonserious AEs occurred in four patients, and two serious AEs (chest discomfort and increased heart rate) occurred in one patient.

The new data support the application that Baxter submitted to the FDA in late 2014 for the approval of BAX 111.

VWD is an autosomal genetic disorder related to quantitative deficits and/or qualitative defects of VWF, the result of which is impaired hemostasis. VWD is the most common hereditary coagulation disorder, occurring in approximately 1% to 2% of the general population. Many patients with VWD may experience mild symptoms, but some patients can experience severe bleeding events similar to those seen in patients with hemophilia.

Source: Baxter; April 17, 2015.

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