An Open-label Extension Study of an Investigational Drug, Fitusiran, in Patients With Moderate or Severe Hemophilia A or B

An Open-label Extension Study of Subcutaneously Administered Fitusiran in Patients With Moderate or Severe Hemophilia A or B Who Have Participated in a Previous Clinical Study With Fitusiran

Primary Objective:

To evaluate the long-term safety and tolerability of fitusiran in male patients with moderate or severe hemophilia A or B

Secondary Objectives:

• To investigate the long-term efficacy of fitusiran
• To characterize the safety and efficacy of concomitantly administered Factor VIII (FVIII), Factor IX (FIX) or bypassing agents (BPA) and fitusiran for treatment of bleeding episodes
• To assess changes in health-related quality of life (QOL) over time
• To characterize antithrombin (AT) reduction and thrombin generation (TG) increase
• To characterize the pharmacokinetics (PK) of fitusiran

It is anticipated that patients in this study will receive treatment with open label fitusiran for approximately 7 years or until fitusiran becomes commercially available, whichever occurs first.

Inclusion Criteria:

• Completed and tolerated study drug dosing in study TDR14767 (ALN-AT3SC-001)
• Male aged ≥18 years
• Moderate or severe, clinically stable hemophilia A or B as evidenced by a laboratory FVIII or FIX level ≤5% at screening. Patients with a FVIII or FIX level >5% at screening will be eligible on provision of a historic laboratory report indicating a trough level ≤5%
• Willing and able to comply with the study requirements and provide written informed consent

Exclusion Criteria:

• Clinically significant liver disease
• Patients known to be human immunodeficiency virus seropositive and have a CD4 count <200 cells/μL
• History of venous thromboembolism
• Current serious mental illness that, in the judgment of the Investigator, may compromise patient safety, ability to participate in all study assessments, or study integrity
• Clinically relevant history or presence of cardiovascular, respiratory, gastrointestinal, renal, neurological, inflammatory, or other diseases that, in the judgment of the Investigator, precludes study participation