An Open-label Extension Study of an Investigational Drug, ALN-AT3SC, in Patients With Moderate or Severe Hemophilia A or B

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

- 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