This study is an international, multicenter, open-label, single arm, prospective clinical trial and will evaluate the efficacy of prophylactic emicizumab administered on a scheduled basis to prevent bleeds in patients with acquired hemophilia A (AHA).

Inclusion Criteria:

• Patients diagnosed with AHA based on a reduced FVIII activity (<50 %) and positive FVIII inhibitor (>0.6 BU/ml) (local laboratory) at time of diagnosis
• Signed informed consent form by the participant or a Person who is legally authorized to sign on behalf of the participant before any study specific tests or procedures are done
• Male or female patients aged 18 years or older at the time of informed consent
• Ability to understand and follow study-related instructions
• Current bleeds due to AHA at the time of screening

Exclusion Criteria:

• Congenital hemophilia A

• Partial or complete remission of AHA (defined as FVIII activity ≥ 50 % and no bleeding and no hemostatic therapy) at the time of screening

• Treatment with aPCC within the last 48 h before first study treatment or planned treatment with aPCC during the course of the study

• Treatment of AHA within the days before study enrollment with more than 100 mg prednisolone (or equivalent) per day or prednisolone for more than 2 days or with other immunosuppressive drugs (e.g. rituximab, cyclophosphamide). IST for other concomitant disorders (e.g. autoimmune disorders) is not an exclusion criterion and can be continued at the investigator's discrétion

• Therapy (current or planned during the emicizumab treatment period) with immunosuppressive or immune modulating drugs that were not already given on a regular basis before first diagnosis of AHA

• Positive lupus anticoagulant at the time of screening

• Severe uncontrolled infection at the time of screening

• Signs of active disseminated intravascular coagulation at the time of screening

• Current treatment for thromboembolic disease or signs of current thromboembolic disease at time of screening

• Patients who are at high risk for TMA (e.g., have a previous medical or family history of TMA), in the investigator's judgment

• Known severe congenital or acquired thrombophilia

• Life expectancy <3 months at the time of screening

• Other conditions that substantially increase risk of bleeding or thrombosis by the discretion of the investigator

• Contraindications according to the local SmPC of emicizumab (see 16.1 Appendix I)

• Current treatment with emicizumab at time of screening

• History of clinically significant hypersensitivity associated with monoclonal antibody therapies or components of the emicizumab injection by the discretion of the investigator

• Concurrent disease, treatment, or abnormality in clinical laboratory tests that could interfere with the conduct of the study, may pose additional risk, or would, in the opinion of the local investigator, preclude the patient's safe participation in and completion of the study

• Addiction or other diseases that preclude the patient from appropriately assessing the nature and scope as well as possible consequences of the clinical study by the discretion of the investigator

• Pregnant or breast-feeding women

• Women of childbearing potential unless women who meet the following criteria:

  1. Post-menopausal (12 months natural amenorrhea or 6 months amenorrhea with serum FSH > 40 U/mL)
  2. Postoperatively (six weeks after bilateral ovariectomy with or without hysterectomy)
  3. Regular and correct use of a contraceptive method with error rate <1% per year such as implants, depot injections, oral contraceptives or intrauterine devices
  4. Sexual abstinence
  5. Vasectomy of the partner

• Men of sexual activity with women of childbearing potential who are not willing to use an effective barrier method of contraception during and up to 3 months after the end of therapy

• Subject is in custody by order of an authority or a court of law

• Receipt of an investigational drug concurrently or within 5 half-lives before administration of the study drug