The B-team: Equal but different?

As a person with haemophilia B, I have known there are differences between haemophilia A and haemophilia B and their respective treatment throughout my life – though I was shocked when I learnt about the impact inhibitors can have when it comes to bleeding. Despite being very rare, as well as difficult to manage, in a recent survey reported by Chaplin et al., many nurses had experience in managing haemophilia B inhibitors. Nurses in the survey also thought extended half-life (EHL) factor products would remain the optimal treatment for haemophilia B in 2025. Ongoing clinical trials for novel molecules like concuzimab and fitusiran signal the start of more treatment options for haemophilia B, and the development of gene therapy has focused on haemophilia B in the first instance. But the fact remains that the pharmaceutical industry has focused on developing treatments for the larger haemophilia A market. Could this have distorted perceptions around treatment? In a further ‘perception bias’ that impacts management, some nurses feel there are differences in bleeding phenotype between haemophilia A and B. Garner et al.'s paper discussing rIX-FX, suggests that treatment adherence is better in haemophilia B due to lower dosing frequency, making it an easier treatment option than for haemophilia A. The patient perception may be somewhat different. While dosing schedules in haemophilia B have been more consistent for longer, there has been less pharmacokinetic modelling in haemophilia B and, arguably, less opportunity for truly tailored treatment. Gene therapy has been shown to be more ‘successful’ for haemophilia B than haemophilia A, but emicizumab has raised questions about the need for gene therapy in haemophilia A. Having an ‘emi-equivalent’ for haemophilia B will raise the same questions and may give people haemophilia B and inhibitors an effective treatment that is as transformative as emicizumab has been in the haemophilia A population.