For Healthcare Professionals

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


About the study

Primary Objective: To characterize the long-term safety and tolerability of fitusiran Secondary Objectives: To characterize the efficacy and long-term efficacy of fitusiran as assessed by the frequency of: Bleeding episodes Spontaneous bleeding episodes Joint bleeding episodes To characterize the effects of fitusiran on health-related quality of life (HRQOL) measures in participants ≥17 years of age

Who can take part

You may be eligible to participate in the study if you meet the following criteria:


Inclusion criteria :

  1. Participant must be at least 12 years of age inclusive, at the time of signing the informed consent
  2. Participants with severe hemophilia A or B who have completed a Phase 3 fitusiran clinical trial
  3. Male
  4. 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:

  1. Completion of a surgical procedure within 14 days prior to screening, or currently receiving additional factor concentrate or BPA infusion for postoperative hemostasis
  2. Current participation in immune tolerance induction treatment (ITI)
  3. Current use of factor concentrates or bypassing agents (BPAs) as regularly administered prophylaxis designed to prevent spontaneous bleeding episodes except for participants requiring factor concentrates or BPAs prophylaxis during the study dosing pause period
  4. Use of compounds other than factor concentrates or BPAs for hemophilia treatment
  5. Current or prior participation in a gene therapy trial
  6. 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

Additional exclusions for participants not currently participating in a fitusiran trial at the time of enrollment in the lower dose cohort:

  1. Clinically significant liver disease
  2. History of arterial or venous thromboembolism

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

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Study Locations

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How to Apply

Contact the study center to learn if this study is a good match for you.

Study’s details



Age (in years)



Phase 3

Participants needed


Est. Completion Date

Dec 18, 2026

Treatment type



Sanofi identifier


Study number


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