Concizumab is a once-daily prophylactic treatment in development for haemophilia A or B with or without inhibitors, and it is potentially the first treatment for haemophilia patients to be delivered subcutaneously using a prefilled, multi-dose pen-injector with a 4 mm, 32 G needle. Aims: To assess handling of the concizumab pen-injector and to assess the patient and caregiver preference of the concizumab pen-injector compared with current injection systems used to administer treatment for haemophilia. Methods: Adult and adolescent patients with haemophilia A or B with or without inhibitors and caregivers currently administering factor replacement or factor VIII (FVIII) mimetic therapy were included. After being trained, participants independently prepared and performed all injection steps and administered an injection into an injection pad. Time to train, time to prepare and inject, and the number of complete injections were measured. Participants evaluated handling and preference via the Haemophilia Device Handling and Preference Assessment Questionnaire (HDHPA).

80 participants were included (44 adults, 21 adolescents, and 15 caregivers; 51% factor, 49% FVIII mimetic therapy). The average time to train was 7min49s, the average time to prepare and inject was 1min21s, and 96% complete injections were achieved. 98% (95% confidence interval [CI] 91–100%) of participants found the concizumab pen-injector ‘easy'or ‘very easy'to use. 96% (95% CI 89–99%) reported that the concizumab pen-injector was ‘easier'or ‘much easier'to use compared to their existing device. 88% (95% CI 78–94%) reported a preference for the concizumab pen-injector, 4% (n = 3) reported a preference for their existing device, and 9% (n = 7) reported ‘no preference’. Discussion/Conclusion(s): Patients and caregivers found the concizumab pen-injector easy to learn how to use and easy to use. Most participants reported a preference for the pen-injector compared with their current injection system.