A Study of Fitusiran (ALN-AT3SC) in Severe Hemophilia A and B Patients Without Inhibitors

Inclusion Criteria:

- Males, ≥12 years of age

- Severe hemophilia A or B without inhibitors

- (Severity confirmed by a central laboratory where FVIII level is <1% or FIX level
is ≤2% at Screening; Inhibitors defined as Nijmegen modified Bethesda assay
inhibitor titer of <0.6 BU/mL at Screening)

- A minimum of 6 bleeding episodes requiring factor concentrate treatment within the
last 6 months prior to Screening.

- Willing and able to comply with the study requirements and to provide written informed
consent and assent

Exclusion Criteria:

- Known co-existing bleeding disorders other than hemophilia A or B

- Antithrombin (AT) activity <60% at Screening

- Co-existing thrombophilic disorder

- Clinically significant liver disease

- Active HCV infection

- HIV positive with a CD4 count of <200 cells/μL

- History of arterial or venous thromboembolism

- Inadequate renal function

- History of multiple drug allergies or history of allergic reaction to an
oligonucleotide or N-Acetylgalactosamine (GalNAc)

- History of intolerance to SC injection(s)

- Any other conditions or comorbidities that would make the patient unsuitable for
enrollment or could interfere with participation in or completion of the study, per
Investigator judgment