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    Poster Networking

    Hemophilia and Rare Bleeding Disorders

    Poster Networking Session

    PB0658 - Low-dose immune tolerance induction in patients with hemophilia A and inhibitor receiving emicizumab prophylaxis: preliminary results of the Brazilian experience

    Monday, June 26, 2023
    18:30 – 19:30 ET
    Room: Exhibition
    Background: The development of inhibitors against factor VIII (FVIII) is the most serious complication of FVIII prophylaxis for patients with hemophilia A. Immune tolerance induction (ITI) is the treatment of choice to eradicate inhibitors. Low-dose ITI has proved to be as efficient as high-dose regimens, but usually takes longer to completely eradicate FVIII inhibitor and presents with a higher frequency of bleeds while inhibitor is still active.

    Aims: This prospective study aims to evaluate the efficacy of low-dose ITI along with emicizumab prophylaxis.

    Methods: Patients with prior high-titer FVIII inhibitors and no previous ITI treatment were included in this study. After the weekly loading dose of emicizumab 3mg/kg for 4 weeks, low-dose ITI (FVIII 50IU/kg 3x/week) was started, along with maintenance emicizumab (1.5mg/kg/week). After immunotolerance is achieved, patients remain on emicizumab prophylaxis for another year, along with FVIII 25IU/kg 1x/week.

    Results: In this preliminary analysis, ten patients (1 adult and 9 children) have enrolled in the study, but only 9 have started ITI (table 1). Four (50%) out of 8 who completed at least 12 weeks of treatment already achieved negative inhibitor. Three patients have already reached success criteria in ITI, while one has a confirmed negative inhibitor assay but no recovery criteria for response. In this group, the median time to reach a negative inhibitor was 6 weeks (range: 2-60 weeks). Three patients have a low-titer positive FVIII inhibitor ( < 2BU/ml) after 2, 65, and 68 weeks of ITI. Three patients remain on ITI, with time on ITI ranging from 1-65 weeks (figure 1). No bleeding episodes were reported under emicizumab prophylaxis.

    Conclusion(s): Preliminary results of this prospective low-dose ITI protocol with emicizumab prophylaxis showed that 50% of patients who completed at least 12 weeks of the first ITI attempt already achieved negative inhibitor. No patient reported bleeding episodes since emicizumab prophylaxis was started.