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Baseline VWF Antigen Level Is Associated with the Outcome of Immune Tolerance Induction Using pdFVIII/VWF Concentrate in Hemophilia A with Inhibitor

Z. Li1, Z. Chen1, X. Cheng1, X. Wu1, G. Li1, Y. Zhen1, S. Cai2, M.-C. Poon3, R. Wu1

1Beijing Children's Hospital Hematology Oncology Center, Beijing, China, 2Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China, 3University of Calgary Cumming School of Medicine, Alberta, Canada

Abstract Number: PB0234

Meeting: ISTH 2020 Congress

Theme: Coagulation and Natural Anticoagulants » Coagulation Factors and Inhibitors

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 September 27, 2023.

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