Sustained Improvement in Health-Related Quality of Life in Patients with Hemophilia A with or without Inhibitors Treated with Fitusiran Prophylaxis
Authors: Cano Viridiana , Bartelt-Hofer José , Hu Wenruo , Andersson Shauna R. , Dasmahapatra Pronabesh , Von Mackensen Sylvia 
Published: November 2021

Abstract
BACKGROUND
Fitusiran is an investigational, subcutaneous (SC), prophylactically administered small interfering RNA (siRNA) therapeutic. It targets antithrombin and restores thrombin generation sufficient to rebalance hemostasis in people with hemophilia A or B, with or without inhibitors. Long-term exposure to fitusiran is being studied in a Phase 1/2, 6-year open-label extension study (NCT02554773) in patients with hemophilia (PwH) A or B with or without inhibitors. Improvement in the health-related quality of life (HRQoL) as measured by Haemophilia Quality of Life Questionnaire for Adults (Haem-A-QoL) total score, and specifically in the physical health domain was previously reported by von Mackensen et al. for PwHA with inhibitors (NCT02554773, N=17, von Mackensen et al. Blood 2020;136(1):23-24). This analysis aimed to present HRQoL changes from baseline to last available measure (LAM), as measured by the Haem-A-QoL total score and domains (filtered by actual treatment exposure following 2 voluntary dosing holds) in PwHA, with or without inhibitors, who continued into the Phase 2 open-label extension study.
METHODS
Participants who completed the Phase 1 study (NCT02035605) were eligible to participate in Phase 2 long-term exposure study (NCT02554773). All participants received fixed monthly doses of 50 mg (N=9) or 80 mg (N=18) of fitusiran. HRQoL data were collected in 3-month lapse periods. Mean changes from baseline to LAM were calculated for the Haem-A-QoL (total score and domains).
RESULTS
As of February 2021, 26 severe and 1 moderate PwHA (13 with, 14 without inhibitors) with mean baseline age (SD) 37.3 (9.7) were treated for up to mean (SD) 33.32 (17.06) months. For the total Haem-A-QoL score and each of 10 domains, mean improvements from baseline to LAM (lower scores denoting better HRQoL) were consistently observed in PwHA (except for the sport & leisure domain that was higher in the non-inhibitor group). Mean estimated reductions (SD) in the Haem-A-QoL total score were -8.33 (13.84) and -9.16 (14.55) while that in the physical health domain score were -13.21 (25.07) and -7.14 (22.80), for PwHA with and without inhibitors respectively (Table 1). When comparing Haem-A-QoL domains in inhibitor to non-inhibitor participants, results suggest a modest favorable trend for non-inhibitor patients (greater reductions in 4 vs 6 domains, respectively).
CONCLUSIONS
Mean improvements in the Haem-A-QoL total scores and 9 out of 10 domains suggest sustained HRQoL improvements in PwHA. Small sample size and outlying results might limit the interpretation. Further research in HRQoL for fitusiran will include a larger population on the new 50 mg every other month dose regimen, and notably Phase III results from NCT03549871 (open-label study in patients switching to fitusiran from previous prophylaxis or bypassing agents) and NCT03754790 (open-label, long-term safety and efficacy study of fitusiran) in various subpopulations.
Figure 1 Figure 1.

Disclosures
Cano: Sanofi Genzyme: Current Employment, Current equity holder in publicly-traded company; Takeda: Ended employment in the past 24 months. Bartelt-Hofer: Sanofi: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company. Hu: Sanofi: Current Employment. Andersson: Sanofi: Current Employment, Current equity holder in publicly-traded company; WEST advisory committee member: Membership on an entity's Board of Directors or advisory committees. Dasmahapatra: Sanofi: Current Employment, Current equity holder in publicly-traded company. Von Mackensen: Biomarin: Speakers Bureau; Novo Nordisk: Consultancy; Sanofi: Consultancy; Sobi: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; University Medical Centre Hamburg-Eppendorf: Current Employment; CSL Behring: Speakers Bureau; Chugai/Roche: Membership on an entity's Board of Directors or advisory committees.