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Recombinant Factor IX Fc fusion protein reduced bleeding in hemophilia B
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Patients with hemophilia B who were treated with prophylactic recombinant Factor IX Fc fusion protein demonstrated reduced annualized bleeding rates, according to phase 3 study results.
The novel recombinant Factor IX Fc fusion protein (rFIXFc) has a prolonged half-life and was developed to reduce the number of necessary injections.
The analysis included 123 male patients with severe hemophilia B — defined as endogenous Factor IX level of ≤2 IU/dL or ≤2% of normal levels — who had been previously treated. Patients were aged at least 12 years.
The study consisted of four arms.
Researchers assigned 63 patients weekly dose-adjusted prophylaxis of 50 IU/kg body weight. Twenty-two patients in this arm received sequential doses of rFIXFc with recombinant Factor IX for comparison.
The second arm comprised 29 patients who received interval-based prophylaxis of 100 IU/kg every 10 days.
In the third arm, 27 patients received 20 IU/kg to 100 IU/kg as needed.
In the fourth arm, 12 patients received perioperative management in doses ranging from 40 IU/kg to 100 IU/kg. Of them, eight returned to one of the other arms after completing surgical rehabilitation.
RFIXFc demonstrated a terminal half-life of 82.1 hours, which was significantly longer than the half-life with recombinant Factor IX (P<.001).
The median annualized bleeding rate was 3 for patients in the weekly dosing arm, 1.4 for patients in the interval-based arm and 17.7 for patients in the as-needed arm. Among patients in these arms, 90.4% experienced bleeding episodes that resolved after one injection.
In the interval-based arm, the dosing intervals extended to 14 days or more in 53.8% of patients during the last 3 months of the study.
Adverse events occurred in 73.9% of patients in the first three arms. Serious adverse events occurred in 10.9% of patients. Researchers noted that these adverse events were typical for patients with hemophilia.
Researchers observed no inhibitor formation in patients and rated hemostasis as excellent or good during all major surgeries.
“This study showed that rFIXFc is safe and effective for the treatment and prevention of bleeding events, including those incurred during major surgeries, in previously treated adolescents and adults with hemophilia B,” the researchers concluded. “The prolonged half-life of rFIXFc allowed for effective prophylaxis, with injections every 1 to 2 weeks. The potential for higher trough levels of rFIXFc or longer intervals between doses may lead to greater use of prophylaxis among patients with hemophilia B.”
Disclosure: See the study for a full list of the researchers’ relevant financial disclosures.
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