Mass General - Division of Clinical Research

• Have a diagnosis of hemophilia A - Patients starting efanesoctocog alfa treatment as per standard of care no more than one month prior to the enrollment date, for either on demand or prophylaxis. Patients starting efanesoctocog alfa treatment for a surgery event may also be enrolled only if the treatment is prescribed at enrollment. - Physician's decision to treat the patient with efanesoctocog alfa is made prior to and independently of participation in the study. - Signed and dated informed consent provided by the patient, or by the patient's legally acceptable representative for patients under the legal age before any study-related activities are undertaken. Assent should be obtained for pediatric patients according to local regulations.

Diagnosed with other known bleeding disorder - Participation in an investigational medicinal product trial at enrollment visit, or intake of an Investigational Medicinal Product within 3 months prior to inclusion in this study - Current diagnosis of a FVIII inhibitor, defined as inhibitor titer ≥0.60 BU/mL "The above information is not intended to contain all considerations relevant to a potential participation in a clinical trial."