Lead-in Study to Collect Prospective Efficacy and Safety Data of Current FVIII Prophylaxis Replacement Therapy in Adult Hemophilia A Participants

Open to males ages 18 years and up

1. Able and willing to provide written informed consent.
2. Males ≥18 years of age.
3. Clinically severe hemophilia A
4. Previous exposure to FVIII therapy
5. No prior history of hypersensitivity or anaphylaxis associated with an FVIII or intravenous immunoglobulin administration.
6. No measurable inhibitor against FVIII
7. Willing to participate and receive treatment in a future Spark hemophilia A gene therapy study.

1. Documented active hepatitis B or C within the past 12 months of Screening
2. Currently on antiviral therapy to treat hepatitis B or C;
3. Documented significant liver disease within the past 6 months of Screening
4. Have serological evidence of HIV-1 or HIV-2
5. Anti-AAV-Spark 200 neutralizing titers ≥1:1
6. Previously received SPK-8011;
7. Previously dosed with any investigational or approved gene therapy product at any time or treated with an investigational drug within the last 12 weeks;
8. Planned surgical procedure in the next 12 months requiring FVIII prophylactic treatment.

9. Any history of chronic infection or other chronic disease, concurrent clinically significant major disease (such as liver abnormalities or type I diabetes) including active malignancy, except for non-melanoma skin cancer, any other condition or any other unspecified reasons that, in opinion of the Investigator or Sponsor, makes the participant unsuitable for participation and dosing in a future clinical study for Spark's hemophilia A gene therapy.

   10. Unable or unwilling to comply with the schedule of visits and/or study assessments

   described in the protocol.