From the Journals

Recombinant factor IX fusion protein benefited untreated patients with hemophilia B



Recombinant factor IX Fc fusion protein was effective, both as prophylaxis and in the treatment of bleeding episodes in previously untreated boys (< 18 years of age) with hemophilia B, according to Beatrice Nolan, MD, of Children’s Health Ireland at Crumlin, Dublin, and colleagues.

PUPs B-LONG is an open-label, single-arm, multicenter, phase 3 trial ( NCT02234310) of rFIXFc in 33 previously untreated patients (PUPs) with hemophilia B; 79% of the patients were younger than 1 year of age at study entry. The primary endpoint was occurrence of inhibitor development, with a secondary endpoint of annualized bleed rate, according to the results of the study, published online in Blood Advances.

At the onset of the study, 22 patients (67%) received on-demand treatment and 11 (33%) started with a prophylactic regimen. Seventeen (77%) of 22 patients who initially received on-demand treatment subsequently switched to prophylaxis, for a total of 28 patients receiving prophylaxis during the study, according to the researchers. Twenty-seven patients (82%) completed the study, and six (18%) discontinued early.

Promising results

The median patient annualized bleeding rate was 1.24 for patients receiving prophylaxis. Most (85%) bleeding episodes required only one infusion for bleed resolution, according to the researchers.

One patient developed a low-titer inhibitor after 11 exposure days to rFIXFc; no high-titer inhibitors were detected. However, 23 patients (70%) had 58 treatment-emergent serious adverse events, of which 2 were assessed as related to treatment (FIX inhibition and hypersensitivity in 1 patient, resulting in withdrawal).

“rFIXFc was generally well tolerated. The incidence of inhibitor development was consistent with other FIX products, with 1 low-titer inhibitor and no high-titer inhibitors detected. In addition, rFIXFc was effective, both as prophylaxis and in the treatment of bleeding episodes,” the researchers concluded.

The PUPs B-LONG study was sponsored by Sanofi and Sobi. Dr. Nolan reported personal fees from Sobi and sponsorship from Sanofi and several other pharmaceutical companies. The other authors reported financial support from a variety of pharmaceutical companies.

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