Prophylactic treatment with the extended half-life recombinant factor IX Fc fusion protein (rFIXFc) prolongs the time to first spontaneous bleeding events and reduces the frequency of first bleeding events compared to on-demand treatment in previously untreated patients with hemophilia B, according to results from the PUPs B-LONG clinical trial.

“Although these results are limited to a small patient group, they suggest that the type of treatment regimen impacts bleed pattern in pediatric [previously untreated participants],” the researchers said.

To investigate the effect of prophylaxis vs on-demand treatment with rFIXFc on spontaneous bleeding events in previously untreated patients with hemophilia B, a team of researchers led by Amy D. Shapiro, MD, conducted a post hoc analysis of the PUPs B-LONG study. The results were presented at the 63rd American Society of Hematology Annual Meeting & Exposition.


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The phase 3, open-label, multicenter study recruited 33 boys with hemophilia B, aged 0 to 2 years who were not previously treated. The primary outcome measure was the percentage of participants with confirmed inhibitor development. 

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Secondary outcome measures were annualized bleeding rates, annualized number of spontaneous joint bleeding episodes, the number of rFIXFc injections with excellent or good, moderate or no treatment response, the total number of exposure days, the total annualized rFIXFc consumption per participant for the prevention and treatment of bleeding episodes, the number of injections and average dose per injection of rFIXFc required to resolve a bleeding episode, and the changes from baseline in rFIXFc incremental recovery.

The results showed that 24 spontaneous bleeding events occurred during the study. Participants receiving prophylaxis had a lower frequency of bleeding events and a longer time to first spontaneous bleeding events compared to those receiving on-demand therapy.

The median time to the first spontaneous bleeding event was 341.5 days for patients being treated with prophylaxis, compared to 183 days for those being treated on-demand.  

Among patients being treated prophylactically, 4 had the first spontaneous bleeding event in a joint, skin, or mucosa. This number was 9 for patients being treated on-demand.

Participants on primary prophylaxis had a lower frequency and longer time to first spontaneous bleeding events compared to participants who switched to prophylaxis from on-demand treatment.

References

Nolan B, Recht M, Rendo P, et al. Prophylaxis with rFIXFc reduces the frequency and delays time to first spontaneous bleed event in previously untreated patients with hemophilia B: a post hoc analysis of the PUPs B-LONG trial. Poster presented at: 63rd American Society of Hematology Annual Meeting & Exposition: December 12, 2021; Atlanta, Georgia.

Study to determine the safety and efficacy of rFIXFc in previously untreated males with severe hemophilia B (PUPs B-LONG). US National Library of Medicine. Last updated July 31, 2020. Accessed December 21, 2021.