Open-Label Single Ascending Dose of Adeno-associated Virus Serotype 8 Factor IX Gene Therapy in Adults With Hemophilia B

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