Long-term Safety and Efficacy Study of Fitusiran in Patients With Hemophilia A or B, With or Without Inhibitory Antibodies to Factor VIII or IX

The estimated total time on study for each participant is up to 55 months which consists of a
screening period of up to 30 days, an open label treatment period of up to 48 months and a
follow up period of up to 6-month after the last dose of fitusiran

Inclusion criteria :

- Participant must be at least 12 years of age inclusive, at the time of signing the
informed consent

- Participants with severe hemophilia A or B who have completed a Phase 3 fitusiran
clinical trial

- Male

- Capable of giving signed informed consent which includes compliance with the
requirements and restrictions listed in the informed consent form (ICF) and in the
protocol. In countries where legal age of majority is above 18 years, a specific ICF
must also be signed by the participant's legally authorized representative

Exclusion criteria:

- Completion of a surgical procedure within 14 days prior to screening, or currently
receiving additional factor concentrate or BPA infusion for postoperative hemostasis

- Current participation in immune tolerance induction treatment (ITI)

- Current use of factor concentrates or bypassing agents (BPAs) as regularly
administered prophylaxis designed to prevent spontaneous bleeding episodes

- Use of compounds other than factor concentrates or BPAs for hemophilia treatment

- Current or prior participation in a gene therapy trial

- Alanine aminotransferase (ALT) and/or Aspartate aminotransferase (AST) >1.5 × upper
limit of normal reference range (ULN) for patients who are naïve to fitusiran at study
start; ALT and/or AST > 5 x ULN for patients who were in the fitusiran arm in the
parent study

The above information is not intended to contain all considerations relevant to a patient's
potential participation in a clinical trial.