The rationale for this study is to further understand and describe the long-term prophylactic effectiveness of efanesoctocog alfa in preventing joint bleeds in a real-life setting.

This is a retrospective-prospective, low-interventional study to evaluate the long-term effectiveness of real-world prophylaxis with efanesoctocog alfa on joint health in people with haemophilia A. Participants in the study must be prescribed efanesoctocog alfa at the discretion of their physicians within 6 months prior to, or at the time of, enrolment. The decision to initiate treatment with efanesoctocog alfa shall be made independently from the decision to include the patients in the study. A broad haemophilia A population (e.g. all severities [mild to severe], all ages, patients with comorbidities and/or concomitant use of anticoagulant/antiplatelet drugs, patients with previous inhibitors to Factor FVIII [FVIII]) will be eligible to enrol. The study will require mandatory on-site visits with joint assessments. A retrospective data collection on patients' haemophilia, medical, and surgical history will be performed, including previous haemophilia treatment and treated bleeding episodes from 12 months prior to initiating treatment with efanesoctocog alfa until enrolment.

The study will start with the enrolment visit during a patient's routine visit to the hospital, to check whether the patient fulfils all the inclusion criteria and none of the exclusion criteria. Study participants will have yearly on-site visits for 24 months or 36 months, depending on the time of enrolment in relation to study closure. Patients will be followed in the study as long as they are treated with efanesoctocog alfa prophylaxis which would be at the physicians' discretion. Patients will also need to agree to document any bleeding episodes they may have during the study in a study-specific paper diary. Joint assessment, Haemophilia Joint Health Score (HJHS), and completion of Patient-reported outcomes (PROs) will be conducted during the on-site visits. For patients included in the Haemophilia Early Arthropathy Detection with Ultrasound (HEAD-US) group, ultrasound joint assessment will also be done at the yearly visits. The end of study (EoS) visit can be performed at the 24-month visit or the 36-month visit, depending on the time of enrolment.

The target is to enroll approximately 250 participants.

Inclusion Criteria:

1. Male or female patient with a diagnosis of haemophilia A.
2. Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol.
3. Prescribed with efanesoctocog alfa prophylactic treatment within 6 months prior to study enrolment or at the latest at the enrolment visit, in accordance with local regulations.
4. Must have received prophylactic treatment(s) with any haemophilia product(s) for at least 12 months prior to being prescribed with efanesoctocog alfa treatment.
5. Have documented pre-study treatment data on haemophilia prophylaxis prescriptions and on treated bleeding episodes from the 12-months prior to being prescribed efanesoctocog alfa treatment and until enrolment into this study.
6. Willing to adhere to the visit schedule and to undergo mandatory study assessment (HJHS, PROs).
7. Willingness and the ability of the patient or their legally designated representative to document all bleeding episodes, including any treatments for those episodes.
8. For HEAD-US subgroup: Accept to undergo annual ultrasound assessment on the index joints (ankles, elbows, knees).

Exclusion Criteria:

1. Acquired haemophilia A and other blood clotting disorders than hereditary haemophilia A.
2. Any positive FVIII inhibitor result (defined as inhibitor titre ≥0.6 Bethesda unit [BU]/mL) from the medical records in connection to the switch to efanesoctocog alfa until the enrolment visit.
3. Enrolment in a concurrent clinical interventional study, or intake of an investigational medicinal product (IMP), including for haemophilia prophylaxis, within 3 months prior to enrolment in this study.
4. Patient not suitable for participation, whatever the reason, as judged by the Investigator, e.g., patient is not able or willing to perform the study assessments.

Qualified researchers may request access to patient level data and related study documents. Patient level data will be anonymized and study documents, if applicable will be redacted to protect the privacy of trial participants.