Ixinity safely controls bleeds in young children with hemophilia B
FDA reviewing request to expand Ixinity's approval to children younger than 12
Treatment with Ixinity (trenonacog alfa) can safely control bleeds in children younger than 12 with severe or moderately severe hemophilia B.
That’s according to data from a Phase 3/4 clinical trial that Medexus Pharmaceuticals, the company that markets Ixinity, presented at the National Hemophilia Foundation’s recent Bleeding Disorders Conference 2023.
The findings “demonstrated the efficacy of Ixinity in the prevention and control of bleeding episodes in pediatric subjects while providing a favorable safety profile,” Johnny Mahlangu, MD, principal investigator of the trial, said in a company press release.
Hemophilia B is caused by the lack or dysfunction of a clotting protein called factor IX (FIX). Ixinity is a replacement therapy containing a lab-made version of this clotting protein.
Ixinity approved in US for hemophilia B patients, 12 and older
Ixinity is approved in the U.S. to prevent or control bleeds in people, 12 and older, with hemophilia B. The U.S. Food and Drug Administration (FDA) is currently reviewing an application requesting the therapy’s approval for younger children.
Medexus sponsored a Phase 3/4 clinical trial (NCT03855280) to test Ixinity in children younger than 12. The study enrolled 21 children. Eight of them had moderately severe hemophilia B, defined as FIX activity levels of at least 1% of normal, but lower than 2% of normal. The other 13 children had severe hemophilia B, with FIX activity levels lower than 1% of normal.
All of the patients had previously been on FIX replacement therapies. In the trial, they all were given prophylactic (preventive) treatment with Ixinity, at doses of 35-75 international units per kilogram of body weight twice weekly. The therapy was also used on demand for bleeding episodes.
Subject to FDA approval of the pediatric indication, the accumulated data should give clinicians greater confidence in administering Ixinity to maintain reliably high factor IX levels long-term, for all patients of all ages with hemophilia B.
Results showed the mean annual bleeding rate while children were on Ixinity was 2.34 bleeds per year. The mean rate of spontaneous bleeds was 0.63 per year.
Seven of the 21 children had no bleeds over the course of the trial, and more than half (61.9%) had no spontaneous bleeds.
In general, the investigators rated Ixinity prophylaxis as “effective,” with three instances where treatment was rated as “partially effective.”
The vast majority (83.8%) of bleeding episodes that occurred in the study resolved after one or two infusions of Ixinity.
Participants rated the therapy’s efficacy as “excellent” or “good” in 78.8% of the episodes where Ixinity was used on demand to control bleeding. All investigators rated the therapy as “effective” for controlling bleeds.
Ixinity generally well-tolerated in study
Ixinity was generally tolerated well in the study. One side effect possibly related to treatment was reported, which was an allergic reaction, judged moderate in severity, resulting in the affected child withdrawing from the study.
No clinically meaningful differences were observed in results for children younger than 6 compared with older children, according to Medexus. Pharmacological data from the trial showed some expected differences in the way the therapy is processed in younger patients compared with adolescents or adults.
Overall, “the results bolster the overall utility of this recombinant [man-made] factor IX agent in the treatment of individuals with hemophilia B,” Mahlangu said.
Mark Fosdal, director of scientific communications at Medexus and co-author of the study, said: “Subject to FDA approval of the pediatric indication, the accumulated data should give clinicians greater confidence in administering Ixinity to maintain reliably high factor IX levels long-term, for all patients of all ages with hemophilia B.”
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