Abstract Number: PB1079
Meeting: ISTH 2020 Congress
Background: Availability of new generation of extended half-life products is revolutionizing the care of hemophilia patients, however, their use in immune tolerance induction (ITI) in hemophilia-B is not well-established.
Aims: We report an Indigenous Canadians boy who was diagnosed with severe hemophilia B at the age of 20 months following prolonged oral cavity bleeding. Genetic studies revealed a large deletion in the FIX gene; his mother was a de-novo carrier.
Methods: Patient was subsequently started on weekly prophylaxis with Fc-fusion-protein rFIX, Alprolix with resolution of bleeding. To minimize the number of required infusions, Alprolix was chosen. Despite this, due to difficult venous access, after 7 exposure-days a Port-a-Cath was inserted. However, during the procedure he developed an anaphylactic reaction and was subsequently diagnosed to have an inhibitor (0.62 BU/ml). After a two-week “holiday” window in which no further infusions of Alprolix were given patient was started on ITI according to the Beutel protocol. Given some reports of successful ITI with Fc-fusion-protein rFVIII in hemophilia-A, Alprolix was chosen. Prior to starting ITI, patient’s peak inhibitor titer was 5.04 BU/ml. The boy was initially commenced on daily Alprolix (80 IU/kg). Over the next 24 weeks he was gradually weaned to every-3-days. Since the start of ITI, patient has had two infusion reactions, both episodes occurring after a >4 day gap between Alprolix infusions.
Results: Patient has achieved Bethesda negativity, a good recovery (47%) and an estimated half-life of ~36 hrs, 24 weeks following the start of ITI. Patient has not needed any bypassing agent, nor had any proteinuria since starting ITI.
Conclusions: To our knowledge this is the first reported case of the use of extended half-life product as “first-line” ITI in a hemophilia-B with inhibitor, and suggests that Alprolix may be a promising option to improve the outcome of ITI in this challenging group of patients.
To cite this abstract in AMA style:Amid A, Perkins H, Bonnefoy A, Gauthier J, Carcao M, Rivard GE, Klaassen R. Inhibitor Formation and Immune Tolerance Induction with Fc-fusion-Protein Recombinant Factor IX in Severe Hemophilia B [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/inhibitor-formation-and-immune-tolerance-induction-with-fc-fusion-protein-recombinant-factor-ix-in-severe-hemophilia-b/. Accessed September 27, 2023.
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