Abstract Number: PB0234
Meeting: ISTH 2020 Congress
Background: The effect of Von Willebrand factor (VWF) on immune tolerance induction (ITI) in severe hemophilia A patients with inhibitor had not been clearly unveiled. Clinical observations also could not demonstrate ITI outcome is better when using concentrates containing VWF than avoiding VWF.
Aims: To describe the relationship between baseline VWF: Ag and ITI outcome under low-dose ITI/immunosuppression (IS) strategy.
Methods: A total of 38 pediatric study subjects (age, 0.8 to 13.2) with severe hemophilia A was recruited from Beijing Children’s hospital in China between September 2016 to July 2019. Subjects had a high titer inhibitor and carrying high inhibitor risk of F8 mutation. VWF: Ag was tested before ITI initiated. Subjects received ITI at ~50 FVIII IU/kg (domestic pdFVIII/VWF) every-other-day alone, or in combination with IS (rituximab and prednisone).
Results: In these subjects, baseline VWF: Ag was median 105.7% (range 63.8-229.1%) and peak historic inhibitor titer of was median 28.4 (range 6.8-416) BU. Seventeen subjects with O type blood group, 21 subjects with non-O type blood group. ITI-alone treatment was given to 19 subjects, ITI-IS to another 19 subjects. The overall success (negative inhibitor) rate was 89.5% in median 8.7 months, no significant difference between two treatment groups. We observed that only baseline VWF: Ag (≥or < 110.5%, HR=0.451, P=0.035) was the predictor of ITI outcome in multivariate analysis rather than inhibitor titer and age. The baseline VWF:Ag also correlated with time to ITI success in patients with non-O blood type (r= 0.723, P＜0.001), but no correlation was observed for type O patients.
Conclusions: Baseline VWF:Ag is a regulator of ITI outcome in low-dose ITI/IS strategy using pdFVIII/VWF concentrate especially when modified by the ABO blood group.
To cite this abstract in AMA style:Li Z, Chen Z, Cheng X, Wu X, Li G, Zhen Y, Cai S, Poon M-, Wu R. Baseline VWF Antigen Level Is Associated with the Outcome of Immune Tolerance Induction Using pdFVIII/VWF Concentrate in Hemophilia A with Inhibitor [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/baseline-vwf-antigen-level-is-associated-with-the-outcome-of-immune-tolerance-induction-using-pdfviii-vwf-concentrate-in-hemophilia-a-with-inhibitor/. Accessed May 18, 2021.
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