Monitoring of Hemlibra Prophylaxis in Children - Real World Data

A. Barg^1,2, T. Livnat^1,2, I. Budnik³, E. Avishai^1,2, I. Tamarin¹, T. Barazani-Brutman^1,2, M. Misgav^1,2, A. Lubetsky^1,2, G. Kenet^1,2

¹Sheba Medical Center, The Israeli National Hemophilia Center and Thrombosis Unit, and The Amalia Biron Research Institute of Thrombosis and Hemostasis, Tel Hashomer, Israel, ²Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel, ³Sechenov First Moscow State Medical University, Department of Pathophysiology, Moscow, Russian Federation

Abstract Number: PB0973

Meeting: ISTH 2020 Congress

Theme: Hemophilia and Rare Bleeding Disorders » Hemophilia - Clinical

Background: Hemlibra, the bispecific monoclonal antibody bridging activated factor (F)IX and FX, is approved as prophylaxis for Hemophilia A (HA) patients with and without inhibitors. Real world data regarding its use in children are scarce.

Aims: To evaluate safety, efficacy and laboratory monitoring in a real world pediatric cohort receiving Hemlibra prophylaxis.

Methods: Plasma samples testing Hemlibra levels, aPTT and Thrombin generation (TG) parameters were obtained before therapy initiation, at weeks 2, 5 and every 3 months.

Results: Forty severe HA children, (median age: 5.5 years, range: 1 month- 18.5 y, including 11 infants) were enrolled, of whom 22 had no inhibitors. Patients were followed for a median of 42 weeks (range 6-100weeks). Twenty patients (50%) experienced zero bleeds. Hemarthroses occurred mostly following trauma. Eight minor surgeries were safely performed in 7 children, yet another procedure (circumcision) was complicated by major bleeding. Bleeding rate was not different between infants (0-1 y) and older children. Positive correlation was found between the length of period treated with Hemlibra and any treated bleeds. Logistic regression indicated that presence of inhibitor significantly reduced bleeding risk .Neither thrombotic complications nor TMA were encountered.
Laboratory analyses disclosed statistically significant increase of Hemlibra plasma levels between week 2 and week 5. The extended aPTT values measured before treatment normalized at week 2 with additional significant shortening at week 5. Both ETP and peak height significantly increased from baseline after 5 weeks; however, TG did not reach the levels of normal controls. No differences were detected between inhibitor and non- inhibitor patients following loading period. Hemlibra levels, aPTT and TG parameters correlated positively. Notably lower TG was observed in very young infants.

Conclusions: Hemlibra prophylaxis was well tolerated in pediatric HA patients. TG interpretation in infants requires caution.

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To cite this abstract in AMA style:

Barg A, Livnat T, Budnik I, Avishai E, Tamarin I, Barazani-Brutman T, Misgav M, Lubetsky A, Kenet G. Monitoring of Hemlibra Prophylaxis in Children – Real World Data [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/monitoring-of-hemlibra-prophylaxis-in-children-real-world-data/. Accessed November 29, 2023.

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