Those in the B-YOND extension trial did not develop an immune response against Alprolix. Adults and adolescents were treated for three years, and children under 12 for 18 months.
“These results come from the longest-term study of an extended half-life therapy for hemophilia B and provide physicians across the globe with important insights and information about the treatment of hemophilia B,” John Pasi, lead investigator of the study, said in a press release.
Results of the study were published in the journal Thrombosis and Haemostasis under the title “Long-term safety and efficacy of extended-interval prophylaxis with recombinant factor IX Fc fusion protein (rFIXFc) in subjects with haemophilia B.”
Alprolix, a recombinant human coagulation factor IX fusion protein (rFIXFc), is an artificial clotting factor therapy that was engineered to be more stable, so it would stay in the body longer. Sobi and Bioverativ are the first companies to use the technology, which is based on human antibody sequencing, to treat hemophilia.
Overall, 116 patients with severe hemophilia were enrolled in the study. The 93 who were older than 12 completed B-LONG. The 23 under 12 completed Kids B-LONG.
Four treatment regimens were used in the trials. Some patients received a preventive dose of Alprolix once a week, and others a preventive dose every eight to 16 days. Still others had a more personalized preventive dosage regimen. And some were given Alprolix only when they had a bleeding episode.
The median number of bleeding episodes per year was low across all treatment regimens — between 2.3 and 2.7. Only patients receiving on-demand therapy had a slightly higher annualized bleeding rate, or ABR — 11.3.
One or two infusions of Alprolix were enough to control bleeding episodes in 97 percent of adults and adolescents, and 95 percent of children, the researchers said.
The B-YOND trial has generated relatively few adverse events, and has been well tolerated, researchers said. The most common events have been headache and the common cold. Twenty of the participants experienced 39 serious events, however.
Investigators said the mild and serious events reported are typical of hemophilia B populations and unrelated to Alprolix treatment. These results were consistent with data from the B-LONG and Kids B-LONG trials, the team said.
“Together with Bioverativ, we remain focused on advancing research to better understand the underlying science and potential benefits of ALPROLIX for people with hemophilia B,” said Krassimir Mitchev, vice president and head of hemophilia therapy efforts at Sobi.