This study is focused on males who have Hemophilia B and who need regular preventive treatment with factor IX protein (FIX) replacement therapy to prevent and also to control their bleeding events. The aim of the study is to gather at least 6 months of information on bleeding events for each individual participant while they continue to use their usual FIX replacement therapy. There is no experimental treatment being tested in this study. The study is informational, and part of a larger program to understand and treat Hemophilia B with a potential experimental new therapy in the future. After you complete this research study, should you be interested and eligible, you may be offered the opportunity to take part in a future study with this new therapy. There is no obligation to agree to taking part in this future study. The study is looking to answer several other research questions to help understand each participant's individual disease characteristics, including: - How often you use FIX replacement therapy, both on a regular basis (prophylaxis) and as needed to treat bleeding events - Measurement of FIX activity (factor IX is a clotting factor) by different laboratories using different types of tests in Hemophilia B patients - Possible complications from the FIX replacement therapy you receive (you will continue to use your usual standard of care FIX prophylaxis for Hemophilia B during the study) - How your quality of life is affected by Hemophilia B - How your joint health is affected by Hemophilia B - How often you visit the emergency room, urgent care center, physician's office, hospital, or have a telemedicine visit as a result of bleeding events - Whether the body makes antibodies (a protein produced by the body's immune system) against the FIX replacement therapy you receive, which could make the drug less effective or could lead to side effects



Eligible Ages
Between 16 Years and 65 Years
Eligible Genders
Accepts Healthy Volunteers

Inclusion Criteria

  1. Previous experience with FIX therapy (≥50 documented exposure days to a FIX protein product such as recombinant, plasma-derived or extended half-life FIX product) with a current stable prophylaxis regimen for >2 months prior to enrollment and intention to use FIX replacement therapy for the duration of the study 2. No known hypersensitivity to FIX replacement product 3. Willing to be contacted about a potential future clustered regularly interspaced short palindromic repeats (CRISPR)-based Factor 9 (F9) gene insertion clinical trial in which they may have the opportunity to screen for enrollment

Exclusion Criteria

  1. Requires anticoagulant therapy 2. Lack of adherence with documentation of bleeds and/or prophylaxis replacement therapy administration in the opinion of the investigator 3. History of FIX inhibitor (clinical or laboratory-based assessment) on 2 or more occasions, as defined in the protocol 4. Bethesda inhibitor titer greater than the upper limit of normal (ULN) at screening 5. Pre-existing antibodies to the Adeno-associated virus serotype 8 (AAV8) capsid 6. Active hepatitis B or C at screening, as defined in protocol 7. If any of the following pre-existing diagnoses are documented: - Cholestatic liver disease - Liver cirrhosis - Portal hypertension; or - Splenomegaly; or - Hepatic encephalopathy 8. History of arterial or venous thrombo-embolic events, as defined in the protocol 9. Any concurrent clinically significant major disease or condition that the investigator deems unsuitable for participation or other acute or chronic medical or psychiatric condition including recent (within the past year) or active suicidal ideation or behavior or laboratory abnormality that may increase the risk associated with study participation or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the participant inappropriate for entry into this study 10. Previous receipt of any AAV-gene based therapy or intent to receive AAV-gene based therapy during the study period NOTE: Other Inclusion/Exclusion Protocol Defined Criteria Apply

Study Design

Study Type
Observational Model
Time Perspective

Arm Groups

ArmDescriptionAssigned Intervention
Cohort 1 Male patients with Hemophilia B on current FIX Replacement Therapy prophylaxis
  • Other: Non-Interventional
    No study treatment will be administered in this study.

Recruiting Locations

University of Texas Health Science Center at Houston
Houston, Texas 77030

More Details

Regeneron Pharmaceuticals

Study Contact

Clinical Trials Administrator


Study information shown on this site is derived from ClinicalTrials.gov (a public registry operated by the National Institutes of Health). The listing of studies provided is not certain to be all studies for which you might be eligible. Furthermore, study eligibility requirements can be difficult to understand and may change over time, so it is wise to speak with your medical care provider and individual research study teams when making decisions related to participation.