Abstract Number: PB0551
Meeting: ISTH 2021 Congress
Theme: Hemophilia and Rare Bleeding Disorders » Hemophilia - Clinical
Background: The current standard of care for patients with moderate and severe haemophilia B (HB) is prophylactic treatment with factor IX (FIX). In Sweden, patients with haemophilia are provided centralized care at one of the three centers in Gothenburg, Malmö or Stockholm. All centers are using a web-based national quality registry for bleeding disorders.
Aims: To use real-world data to describe HB patients being on prophylaxis and to compare treatment and outcomes in patients before and after switching from a standard half-life (SHL) FIX product to extended half-life recombinant FIX Fc fusion protein (rFIXFc).
Methods: Patient characteristics and treatment data from the Swedish haemophilia registry were collected and assessed for all HB patients aged ≥13 years being treated prophylactically for ≥6 months at the cut-off date (November 18, 2020). A retrospective within-patient comparison of prescribed dose, patient-reported factor consumption, number of injections, and annualised bleeding rate (ABR) of patients who switched from SHL FIX to rFIXFc, with ≥6 months documented prophylactic treatment pre- and post-switch was performed.
Results: Out of 38 HB patients receiving rFIXFc treatment the majority (35 patients; 92%) were on prophylactic treatment (Figure 1). In within-patient analyses before and after switching to rFIXFc median (IQR) follow-up time was 609.0 (426.5-657.5) days (n=19); median (IQR) prescribed dose decreased by 42% from 77.4 (42.5-82.0) to 45.0 (37.0-63.4) IU/kg/week (n=14); median (IQR) patient-reported factor consumption decreased by 37% from 68.1 (45.9-91.2) to 42.8 (37.8-50.7) IU/kg/week (n=16); median (IQR) number of injections per week decreased from 2.0 (2.0-3.2) to 1.0 (1.0-1.0) (n=17); median (IQR) ABR was 0.0 (0.0-1.0) on SHL FIX and 0.0 (0.0-0.0) on rFIXFc (n=18) (Table 1).
Study population
| Patient characteristics | SHL FIX (n=25) | rFIXFc (n=21) |
| Severity of haemophilia; n (%) Severe Moderate |
22 (88.0) 3 (12.0) |
13 (61.9) 8 (38.1) |
| Age (years) Mean (SD) Median (IQR) |
46.3 (22.7) 48.0 (24.0-65.0) |
39.5 (18.9) 34.0 (26.0-53.7) |
| Age distribution (years); n (%) 13-17 years 18-49 years ≥50 years |
0 (0.0) 13 (52.0) 12 (48.0) |
2 (9.5) 13 (61.9) 6 (28.6) |
| Within-patient comparison | SHL FIX (n=19) | rFIXFc (n=19) |
| Prescribed prophylactic dose; IU/kg/week Mean (SD) Median (IQR) Missing; n |
69.8 (27.5) 77.4 (42.5-82.0) 5 |
51.8 (20.1) 45.0 (37.0-63.4) 5 |
| Patient-reported consumption; IU/kg/week Mean (SD) Median (IQR) Missing; n |
67.5 (34.3) 68.1 (45.9-91.2) 3 |
46.9 (15.2) 42.8 (37.8-50.7) 3 |
| Number of injections per week; n Mean (SD) Median (IQR) Missing; n |
2.3 (0.8) 2.0 (2.0-3.2) 2 |
1.1 (0.3) 1.0 (1.0-1.0) 2 |
| Annualized bleeding rates (ABRs) Mean (SD) Median (IQR) Missing; n |
1.1 (2.1) 0.0 (0.0-1.0) 1 |
0.2 (0.7) 0.0 (0.0-0.0) 1 |
Analyses of the haemophilia B population aged ≥13 years treated prophylactically for ≥6 months
Conclusions: Swedish real-world data suggest that patients on prophylaxis switching from a SHL FIX product to rFIXFc reduced factor consumption and injection frequency with an at least maintained level of bleed protection.
To cite this abstract in AMA style:
Olsson A, Myrin-Westesson L, Baghaei F, Holmström M, Olsson E, Magnusson M, Ranta S, Astermark J, Gretenkort Andersson N, Thanner J, Szamosi J, Sennfält K. Real-world Usage of rFIXFc in Sweden: A Report from the Swedish National Registry for Bleedings Disorders [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/real-world-usage-of-rfixfc-in-sweden-a-report-from-the-swedish-national-registry-for-bleedings-disorders/. Accessed May 20, 2022.« Back to ISTH 2021 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/real-world-usage-of-rfixfc-in-sweden-a-report-from-the-swedish-national-registry-for-bleedings-disorders/