Study to Test the Safety and How Well Patients With Severe Hemophilia A Respond to Treatment With BAY 2599023 (DTX 201), a Drug Therapy That Delivers a Healthy Version of the Defective Factor VIII Gene Into the Nucleus of Liver Cells Using an Altered, Non-infectious Virus (AAV) as a "Shuttle"

Prior treatment

• Current evidence of measurable inhibitor against factor VIII, prior history of inhibitors to FVIII protein or clinical history suggestive of inhibitor.
• Currently on antiviral therapy for hepatitis B or C.
• Detectable antibodies reactive with AAVhu37capsid.
• Participated in a gene transfer trial within the last 52 weeks or in a clinical trial with an investigational product within the last 12 weeks.

Other illness

• History of allergic reaction to any FVIII product.
• Evidence of active hepatitis B or C.
• Significant underlying liver disease.
• Participant with another bleeding disorder that is different from hemophilia A (e.g., von Willebrand disease, hemophilia B).
• Known or suspected hypersensitivity or allergic reaction to trial product(s) or related FVIII products or any component of BAY2599023 (DTX201), or a contraindication to prednisolone

Lab values

• Serological evidence of HIV-1 or HIV-2 with CD4 counts ≤200/mm\*3; HIV+ and stable participants with CD4 count \>200/mm\*3 and undetectable viral load are eligible to enroll.

Other

• Clinically relevant findings in the physical examination considered critical by the treating physician, including obesity with BMI \> 35 kg/m\*2

• Males age 18 years or older.
• Confirmed diagnosis of hemophilia A as evidenced by their medical history with plasma FVIII activity levels \< 1% of normal or at screening.
• Have \>150 exposure days (EDs) to FVIII concentrates (recombinant or plasma-derived).
  • If on prophylaxis, are required to be willing to stop prophylactic treatment at specified time points throughout the study or If on-demand: should have had \> 4 bleeding events in the last 52 weeks
  • \- Agree to use reliable barrier contraception.