This clinical trial study uses a modified adeno-associated virus (AAV) to carry the human factor VIII gene to the liver. In the liver is where factor VIII protein is made. The study product, SPK-8011, is available only to participants in this research study. This product has not been approved yet for use in the general public. This will be the first hemophilia A gene transfer research study done in the United States. To learn more about the benefits and risks related to this study, please contact Dr. Lindsey George at (267) 425-0132.In order to participate in this study, you must be male, 18 years or older, have hemophilia A with FVIII activity levels less or equal to 2%, a history of bleeding that requires prophylaxis or on demand therapy, and no history of inhibitor to factor VIII. This study requires a number of visits over the course of 12 months. All costs related to participation in the study will either be covered or reimbursed by the Sponsor of the study, Spark Therapeutics, and participants will be compensated for their time.