A Research Study Investigating Denecimig (Mim8) in Adults With Acquired Haemophilia A

• Denecimig (Drug): Participants will receive subcutaneous (s.c.) injections of denecimig.

Primary outcomes

• Number of treated bleeds [From treatment initiation (week 0) until end of main part (week 12)]: Measured as count of treated bleeds.

Secondary outcomes

• Number of treated bleeds [From initiation of extension part (week 13) up until end of treatment (week 52)]: Measured as count of treated bleeds.
• Number of clinically relevant new bleeds [From treatment initiation (week 0) up until end of treatment (week 52)]: Measured as count of new bleeds.
• Days of treatment with bypassing agent (BPAs) or coagulation factor VIII (FVIII) products for management of bleeding episodes [From treatment initiation (week 0) up until end of treatment (week 52)]: Measured as count of bleeds.
• Occurrence of infections [From treatment initiation (week 0) up until end of study (week 73)]: Measured as count of infections.
• Occurrence of antidrug antibodies [From treatment initiation (week 0) up until end of study (week 73)]: Measured as count of antidrug antibodies.
• Denecimig plasma concentration [From treatment initiation (week 0) up until end of treatment (week 52)]: Measured as microgram per milliliter (μg/mL).

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Informed consent obtained before any study-related activities. Study-related activities are any procedures that are carried out as part of the study, including activities to determine suitability for the study.
* Male or female participants (sex assigned at birth, inclusive of all gender identities) newly diagnosed with acquired haemophilia A (AHA) prior to signing the informed consent form, with AHA diagnosis (FVIII activity lesser than (<) 50 percentage (%) and FVIII inhibitors greater than (>) 0.6 Bethesda units \[BU\]) confirmed at screening.
* Treatment-requiring bleed(s) due to AHA from diagnosis and until screening.
* The participant is capable of following study procedures and able to seek medical attention when needed.

Exclusion Criteria:

* Female who is pregnant, breast-feeding or intends to become pregnant or is of childbearing potential and not using an adequate and highly effective contraceptive method.
* Previous or current thromboembolic disease or eventsa (with the exception of previous catheter associated thrombosis for which anti-thrombotic treatment is not currently ongoing) or risk of thromboembolic disease.
* Life expectancy <3 months at the time of screening, as evaluated by the investigator.
* Therapy with immunosuppressive or immune modulating drugs for treatment of AHA (other than less than or equal to (≤) 2 days of prednisolone (or equivalent) for AHA at a dose ≤100 mg per day) prior to screening.
* Immunosuppressive therapy (IST) initiated prior to AHA diagnosis for other medical conditions (e.g., other autoimmune disorders) is permitted, provided it was initiated greater than or equal to (≥) 6 months prior to screening, has been maintained at a stable dose and regimen since initiation, and is expected to remain at a stable dose and regimen at least during the main treatment period (Weeks 0-12).

• Clinical Transparency (dept. 2834), Study director, Novo Nordisk A/S