A Gene Transfer Study for Hemophilia A

Inclusion Criteria: * Males age 18 years or older * Confirmed diagnosis of hemophilia A as evidenced by their medical history with baseline FVIII activity levels \<=2% * Have received \>150 exposure days (EDs) to FVIII concentrates or cryoprecipitate * Have no prior history of allergic reaction to any FVIII product * Have no measurable inhibitor against FVIII as assessed by the central laboratory and have no prior history of inhibitors to FVIII protein and no clinical signs or symptoms of decreased response to FVIII administration * Agree to use reliable barrier contraception Exclusion Criteria: * Evidence of active hepatitis B or C * Currently on antiviral therapy for hepatitis B or C * Have significant underlying liver disease * Have serological evidence\* of HIV-1 or HIV-2 with CD4 counts ≤200/mm3 and who are on an antiretroviral drug regimen (\* participants who are HIV+ and stable with CD4 count \>200/mm3 and undetectable viral load are eligible to enroll) * Have detectable antibodies reactive with AAV-Spark200 capsid * 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