Presentation Details
| Real-World Use of Recombinant Factor IX Fusion Protein in Previously Untreated Patients with Congenital Hemophilia B from the ATHN 8 Study Courtney D.Thornburg1, Martin Chandler2, Lynn Malec3, Matthew Manuel2, Carrie O'Neill2, Michael Recht4, 5, Elizabeth Taggart2, Hongseok Kim6, Vidhi Desai6, Hiren Shah6, Shannon L.Carpenter7. 1Rady Children’s Hospital San Diego, San Diego, CA, USA.2American Thrombosis and Hemostasis Network, Rochester, NY, USA.3Versiti Blood Research Institute, Waukesha, WI, USA.4Yale University School of Medicine, New Haven, CT, USA.5National Bleeding Disorders Foundation, New York, NY, USA.6CSL Behring, King of Prussia, PA, USA.7Children’s Mercy Hospital, Kansas City, MO, USA |
Abstract
Background: People with hemophilia are at risk of developing neutralizing inhibitors to factor products. Previously untreated patients (PUPs) are particularly vulnerable, and development of inhibitors is most likely to occur within 20 exposure days (EDs). Recombinant factor IX fusion protein (rIX-FP) was shown to be safe and efficacious in preventing bleeding episodes among 12 PUPs with hemophilia B (NCT02053792); 1 of the 12 participants, an 11-year-old male with deletion of exons 7 and 8 of the FIX gene, developed factor IX (FIX) inhibitors. Large gene deletions are a known risk factor for inhibitor development. While some risk factors for inhibitor development are known, the ability to accurately predict who is at the highest risk for inhibitor development remains a challenge. To address this knowledge gap, a study was conceptualized to understand the variables contributing to inhibitor development. The American Thrombosis and Hemostasis Network (ATHN) ATHN 8 study is a US-based longitudinal cohort study of PUPs with moderate or severe hemophilia A or B (ATHN 8; NCT03818529). In the ATHN 8 study, 3 of 39 participants with hemophilia B developed inhibitors within the first 50 EDs. Here we present a subset of PUPs with hemophilia B from the ATHN8 study who received rIX-FP. Objectives: This report evaluates inhibitor development in PUPs with congenital hemophilia B who received rIX-FP in the real-world setting. Methods: Data were collected for a subset of PUPs from ATHN 8 with hemophilia B who were born between January 2010 and September 2021 and received rIX-FP. Participants were enrolled at ATHN-affiliated sites until 50 clotting factor EDs, development of a confirmed neutralizing inhibitor, or study closure. Results were summarized descriptively. Results: The study enrolled 10 males with moderate-to-severe hemophilia B who received rIX-FP. Among these 10 participants, none developed an inhibitor during the study. Of these, 60% (6/10) had at least 50 EDs. Mean FIX EDs was 45 days. Eight participants (80%) had severe hemophilia and were less than 1 month old (60%) at the time of their first bleed (Table 1 shows additional baseline demographics). Conclusions: In the subanalysis of participants with hemophilia B who received rIX-FP, none developed inhibitors. This included 7 participants with more than 20 EDs, of whom 6 had more than 50 EDs. This is consistent with what was seen in the clinical trial.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.