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Emicizumab prophylaxis in people with severe haemophilia A without inhibitors: outcomes from the UK Haemophilia Centre Doctors’ Organisation

1Manchester Royal Infirmary, Manchester, England, United Kingdom, 2National Haemophilia Database, Manchester, England, United Kingdom, 3Royal Free Hospital, London, England, United Kingdom, 4Medical School of Cardiff University, Cardiff, Wales, United Kingdom, 5Oxford Haemophilia and Thrombosis Centre, Oxford, England, United Kingdom, 6Great Ormond Street Hospital for Children, NHS Foundation Trust, London, England, United Kingdom, 7University Hospitals Birmingham NHS Foundation Trust, Birmingham, England, United Kingdom, 8Oxford University Hospitals NHS Foundation Trust, Oxford, England, United Kingdom, 9East Kent Hospitals University NHS Trust, Faculty of Health and Wellbeing, Canterbury Christ Church University, Canterbury, England, United Kingdom, 10Newcastle Haemophilia Comprehensive Care Centre, Royal Victoria Infirmary, Newcastle upon Tyne, England, United Kingdom

Abstract Number: OC 30.1

Meeting: ISTH 2022 Congress

Theme: Hemophilia and Rare Bleeding Disorders » Hemophilia - Clinical

Background: The uptake of emicizumab in persons with severe haemophilia A (pSHA) without inhibitors is heterogeneous. We present UK outcomes since its introduction in 2019.

Aims: To determine bleeding outcomes in pSHA treated with emicizumab in UK clinical practice

Methods: An observational study was conducted of 673 pSHA who switched from FVIII prophylaxis to emicizumab between 01/08/19 and 30/09/21. A within-person comparison of annualised bleed (ABR) and joint-bleed rate (AJBR) with prior FVIII prophylaxis was conducted in people with ≥6 months pre and post-switch Haemtrack home-therapy data using Wilcoxon signed rank test. Change in proportion reporting zero-treated bleeds was analysed using the McNemar test.

Results: Emicizumab was prescribed to 673 non-inhibitor pSHA, 36.9% of the UK-registered cohort, including 85 (12.6%) with an inhibitor history. A within-person comparison with previous FVIII prophylaxis was conducted in 401 pSHA broken down by age (table 1). A within-person sub-analysis of 144 people reporting bleeding (table 2) showed that 73% (105/144) had a reduced bleeding after switching (p < 0.001). Relatively few subjects had target joints using ISTH criteria; 35 switchers had 51 target joints and 45 non-switchers had 69 target joints. After a median 21 months follow-up, 74% of emicizumab switchers experienced fewer and 6% more target joints versus 42% fewer and 33% more target joints in non-switchers (p = 0.004). Recurrent FVIII inhibitors were reported in 4/85 (4.7%) people at risk. One person (0.15%) developed a low level anti-drug antibody (ADA).

Conclusion(s): Switching to emicizumab resulted in significantly improved bleed control in all age groups (p < 0.001) and in 65-80% no treated bleeds were reported. In subjects who reported bleeding, clinically and statistically significant reductions in ABR were observed. Target joints resolved more frequently than in people who continued FVIII prophylaxis. ADAs were uncommon and recurrent FVIII inhibitors occurred in ~5% of those at risk.

To cite this abstract in AMA style:

Wall C, Xiang H, Palmer B, Chowdary P, Collins P, Hall G, Mathias M, Percy C, Sartain P, Shapiro S, Stephensen D, Talks K, Hay C. Emicizumab prophylaxis in people with severe haemophilia A without inhibitors: outcomes from the UK Haemophilia Centre Doctors’ Organisation [abstract]. https://abstracts.isth.org/abstract/emicizumab-prophylaxis-in-people-with-severe-haemophilia-a-without-inhibitors-outcomes-from-the-uk-haemophilia-centre-doctors-organisation/. Accessed November 30, 2023.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/emicizumab-prophylaxis-in-people-with-severe-haemophilia-a-without-inhibitors-outcomes-from-the-uk-haemophilia-centre-doctors-organisation/