The purpose of this study is to evaluate the safety of single ascending IV doses of a Factor IX (FIX) Gene Therapy in up to 16 Adults with Hemophilia B.

Hemophilia B is a genetic X-linked bleeding disorder caused by a deficiency in blood-clotting Factor IX (FIX) activity. FIX is synthesized in the liver and circulates in the blood as a proenzyme. Current treatment for hemophilia B is based on replacement of the deficient FIX with IV injections of recombinant FIX protein prophylactically or as needed to treat bleeding episodes. This clinical program will test a gene transfer approach involving the use of a gene delivery vector carrying a FIX gene. This first-in-humans study is intended to evaluate the safety, kinetics, and if possible, the dose of AskBio009 required to achieve stable plasma FIX activity between 10% and 40% of normal activity.

Inclusion Criteria:

• Males age 18-75 years, inclusive
• Established hemophilia B with ≥3 hemorrhages per year requiring treatment with exogenous FIX OR use of FIX prophylaxis because of history of frequent bleeding episodes
• Plasma FIX activity ≤2% (<1% for first cohort; then per protocol)
• Negative for active Hepatitis C virus (HCV), defined as Hepatitis C virus antibody negative and negative (undetectable) PCR test for plasma Hepatitis C virus ribonucleic acid (RNA) OR if Hepatitis C virus antibody positive must have ≥2 consecutive negative (undetectable) PCR tests for plasma HCV RNA at least 3 months apart, and negative at screening

Exclusion Criteria:

• Family history of inhibitor to FIX protein or personal laboratory evidence of having developed inhibitors to FIX protein at any time (>0.6 Bethesda Units on any single test)

• Documented prior allergic reaction to any FIX product

• Detectable AAV8 neutralizing antibodies

• Markers of hepatic inflammation or overt or occult cirrhosis as evidenced by one or more of the following:

  • Platelet count <175,000/μL
  • Albumin ≤3.5 g/dL
  • Total bilirubin >1.5 x ULN and direct bilirubin ≥0.5 mg/dL
  • Alkaline phosphatase >2.0 x ULN
  • ALT or AST >2.0 x ULN (except for subjects who are HIV infected)
  • Liver biopsy in the past indicating moderate or severe fibrosis (Metavir staging of 2 or greater)
  • History of ascites, varices, variceal hemorrhage or hepatic encephalopathy

Takeda provides access to the de-identified individual participant data (IPD) for eligible studies to aid qualified researchers in addressing legitimate scientific objectives (Takeda's data sharing commitment is available on https://clinicaltrials.takeda.com/takedas-commitment?commitment=5). These IPDs will be provided in a secure research environment following approval of a data sharing request, and under the terms of a data sharing agreement.

IPD from eligible studies will be shared with qualified researchers according to the criteria and process described on https://vivli.org/ourmember/takeda/. For approved requests, the researchers will be provided access to anonymized data (to respect patient privacy in line with applicable laws and regulations) and with information necessary to address the research objectives under the terms of a data sharing agreement.