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Real-world Usage of rFIXFc in Sweden: A Report from the Swedish National Registry for Bleedings Disorders

A. Olsson1, L. Myrin-Westesson1, F. Baghaei1, M. Holmström2,3, E. Olsson2, M. Magnusson2,4,5, S. Ranta4, J. Astermark6, N. Gretenkort Andersson7, J. Thanner8, J. Szamosi8, K. Sennfält8

1Region Västra Götaland, Sahlgrenska University Hospital, Department of Medicine, Gothenburg, Sweden, 2Coagulation Unit, Department of Hematology, Karolinska University Hospital, Stockholm, Sweden, 3Dept of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden, 4Pediatric Coagulation Unit, Astrid Lindgren Children´s hospital, Karolinska University hospital, Stockholm, Sweden, 5MMK and CLINTEC, Karolinska Institutet, Stockholm, Sweden, 6Department of Translational Medicine and Department of Hematology, Oncology and Radiation Physics, Lund University, Skåne University Hospital, Lund, Sweden, 7Department for Paediatric Haematology and Oncology, Children´s Hospital, University Hospital Skåne and Department of Clinical Sciences, Paediatrics, Lund University, Lund, Sweden, 8Swedish Orphan Biovitrum AB, Stockholm, Sweden

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.

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