• Signed Informed Consent/Assent Form

• Age ≥18 years at time of signing Informed Consent Form

• Ability to comply with the study protocol, in the investigator's judgment

• Diagnosis of AHA based on a reduced FVIII activity (\<50 %) and positive FVIII inhibitor (\>0.6 BU/ml) at screening (local laboratory)

• Current bleeding due to AHA at the time of screening

• Plan to be adherent to emicizumab prophylaxis during the study

• For women of childbearing potential who meet the following criteria:

• Refrain from heterosexual intercourse or use contraceptive methods that result in a failure rate of \<1% per year during the study period A woman with ≥ 12 continuous months of amenorrhea with no identified cause other than menopause and has not undergone surgical sterilization (removal of ovaries and/or uterus). use of combined oral or injected hormonal contraceptive, bilateral tubal ligation, male sterilization, hormone- releasing intrauterine devices, and copper intrauterine devices.