A Study to Investigate the Efficacy and Safety of Fitusiran Prophylaxis in Male Participants Aged 1 to Less Than 12 Years With Hemophilia A or B

NCT07285460 | Recruiting Phase 3 DMC FDA Drug

• 3 other identifiers: EFC17905U1111-1280-70282025-521858-42
• Study Type: interventional
• Target: 85
• Locations: 11 countries
• Sites: 24

Brief Summary

This is a parallel, Phase 3, two-arm, open-label study to evaluate the efficacy and safety of treatment with fitusiran prophylaxis administered to male pediatric participants (aged 1 to \<12 years) who have severe hemophilia A or B, with or without inhibitory antibodies to FVIII or FIX. Number of participants: Approximately 85 participants will be enrolled into the study:

• Approximately 60 fitusiran-naïve participants with severe hemophilia A or B, with or without inhibitors (fitusiran-naïve arm), and
• Approximately 25 participants with severe hemophilia A or B with inhibitors rolling over from the EFC15467\* dose confirmation study (roll-over arm).
• Fitusiran has been investigated in the pediatric population in study EFC15467, which enrolled male participants aged 1 to \<12 years with hemophilia A or B with inhibitors to examine the safety and tolerability of fitusiran in the pediatric population. Participants will be enrolled into 1 of 2 arms:
• Fitusiran-naïve: these participants have not previously received fitusiran, and they will undergo screening and study eligibility assessments. Once enrolled, they will go through a 24-week standard of care (SOC) period before starting fitusiran prophylaxis.
• Roll-over participants from the EFC15467 study: only participants who are still on active treatment in study EFC15467 and consenting to study EFC17905 will be eligible to roll over. They will not need to undergo screening or further eligibility assessments. They will directly enroll into the fitusiran treatment period and continue treatment on their current fitusiran dose. The duration of fitusiran treatment will be up to 160 weeks for the fitusiran-naïve arm and up to 60 weeks for the roll-over arm.

Conditions

Hemophilia

Outcome Measures

Primary Outcomes (1)

• Annualized treated bleeding rate (ABR) in the fitusiran primary efficacy period and in the SOC period

  A bleeding episode is defined as any occurrence of hemorrhage that requires administration of CFCs or BPAs

  Day 85 to Day 421 (fitusiran primary efficacy period); Day -168 to Day -1 (SOC period)

Secondary Outcomes (10)

• Annualized spontaneous bleeding rate (AsBR) in the fitusiran primary efficacy period and in the SOC period

  Day 85 to Day 421 (fitusiran primary efficacy period); Day -168 to Day -1 (SOC period)

• Annualized joint bleeding rate (AjBR) in the fitusiran primary efficacy period and in the SOC period

  Day 85 to Day 421 (fitusiran primary efficacy period); Day -168 to Day -1 (SOC period)

• ABR in the fitusiran treatment period (160 weeks) for fitusiran-naïve participants

  Day 1 to Day 1121

• ABR in the fitusiran treatment period (60 weeks) for rolled-over participants

  Day 1 to Day 421

• Change in physical activity

  From Day 1 to Day 421; From Week -24 to Day -1

Study Arms (2)

Fitusiran-naïve arm

EXPERIMENTAL

Participants will go through a 24-week standard of care (SOC) period before receiving a selected dose of fitusiran at regular interval. If a fitusiran dose adjustment is needed during the study, participants will follow a specific dosing regimen as per study protocol.

Drug: Fitusiran; Biological: Clotting factor concentrates (CFC) or bypassing agents (BPA); Biological: Antithrombin concentrate (ATIIIC)

EFC15647 roll-over arm

EXPERIMENTAL

Participants will continue receiving their current fitusiran dose from EFC15467. If a fitusiran dose adjustment is needed during the study, participants will follow a specific dosing regimen as per study protocol.

Drug: Fitusiran; Biological: Clotting factor concentrates (CFC) or bypassing agents (BPA); Biological: Antithrombin concentrate (ATIIIC)

Interventions

Fitusiran DRUG

Pharmaceutical form: solution for injection in PBS Route of administration: subcutaneous

Also known as: SAR439774, Qfitlia™

EFC15647 roll-over arm; Fitusiran-naïve arm

Clotting factor concentrates (CFC) or bypassing agents (BPA) BIOLOGICAL

Pharmaceutical form: solution for injection Route of administration: intravenous injection

EFC15647 roll-over arm; Fitusiran-naïve arm

Antithrombin concentrate (ATIIIC) BIOLOGICAL

Pharmaceutical form: solution for injection Route of administration: intravenous injection

EFC15647 roll-over arm; Fitusiran-naïve arm

Eligibility Criteria

• Age: 1 Year - 11 Years
• Sex: male
• Healthy Volunteers: No
• Age Groups: Child (0-17)

You may qualify if:

• Participants not previously exposed to fitusiran are eligible to be included in the study only if all of the following criteria apply:
• Participant must be 1 to \<12 years of age at the time of enrollment.
• Participants must have severe hemophilia A or B (FVIII \<1% or FIX ≤2%) as evidenced by a central laboratory measurement at screening or documented medical record evidence.
• Participants must meet inhibitor or non-inhibitor status as defined below:
• Inhibitor:
• Requiring use of BPA for prophylaxis or BPA as on-demand therapy for any bleeding episodes for at least the last 3 months prior to screening, and meet one of the following Nijmegen-modified Bethesda assay results criteria:
• Inhibitor titer of ≥0.6 BU/mL at screening, OR
• Inhibitor titer of \<0.6 BU/mL at screening with medical record evidence of 2 consecutive titers ≥0.6 BU/mL, OR
• Inhibitor titer of \<0.6 BU/mL at screening with medical record evidence of 1 inhibitor titer ≥0.6 BU/mL and a history of anamnestic response, or severe allergic reaction (eg, anaphylaxis) or nephrotic syndrome
• Non-inhibitor:
• Requiring use of clotting factor concentrates (CFCs) for prophylaxis or CFCs as on-demand therapy for any bleeding episodes for at least the last 3 months prior to screening, and meet each of the following criterion:
• Nijmegen-modified Bethesda assay inhibitor titer of \<0.6 BU/mL at screening, AND
• No use of BPA to treat bleeding episodes for at least the last 3 months prior to screening
• Participants must have adequate peripheral venous access, as determined by the Investigator, to allow the blood draws required by the study protocol.
• Male: There are no contraceptive requirements for this study except where required by local regulations.

You may not qualify if:

• Participants not previously exposed to fitusiran are excluded from the study if any of the following criteria apply:
• Known co-existing bleeding disorders other than hemophilia A or B.
• Presence of clinically significant liver disease.
• History of antiphospholipid antibody syndrome.
• History of arterial or venous thromboembolism, unrelated to an indwelling venous access
• Any condition (eg, medical concern), which in the opinion of the Investigator, would make the participant unsuitable for dosing or which could interfere with the study compliance, the participant's safety and/or the participant's participation in the completion of the treatment period of the study.
• History of multiple drug allergies or history of allergic reaction to an oligonucleotide or GalNAc.
• Subjects with a central or peripheral indwelling catheter, with a history of venous access complications (such as infections, thrombosis) leading to hospitalization and/or systemic anticoagulation therapy in the last 12 months.
• At screening, anticipated need of surgery during the study or planned surgery scheduled to occur during the study.
• Completion of a surgical procedure within 14 days prior to screening, or currently receiving additional BPA infusion for postoperative hemostasis.
• History of intolerance to SC injection(s).
• Current participation in ITI therapy.
• The use of emicizumab (Hemlibra®) or any non-factor bleed management treatment within 6 months prior to screening
• Prior gene therapy
• Current or future participation in another clinical study, scheduled to occur during this study, involving an investigational product other than fitusiran or an investigational device.

Sponsors & Collaborators

• Sanofi: lead

Study Sites (24)

The Luskin Orthopaedic Institute for Children- Site Number : 8400013

Los Angeles, California, 90007, United States

RECRUITING

The Center for Inherited Blood Disorders- Site Number : 8400009

Orange, California, 92868, United States

RECRUITING

Cure 4 The Kids Foundation- Site Number : 8400001

Las Vegas, Nevada, 89147, United States

RECRUITING

Hackensack Meridian Health - Hackensack University Medical Center- Site Number : 8400008

Hackensack, New Jersey, 07601, United States

RECRUITING

Investigational Site Number : 0560002

Brussels, 1020, Belgium

RECRUITING

Investigational Site Number : 0560001

Brussels, 1200, Belgium

RECRUITING

Hospital das Clinicas da Faculdade de Medicina de Ribeirao Preto- Site Number : 0760003

Ribeirão Preto, São Paulo, 14049-900, Brazil

RECRUITING

Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo- Site Number : 0760004

São Paulo, 05403-000, Brazil

RECRUITING

Investigational Site Number : 1240003

Montreal, Quebec, H3T 1C5, Canada

RECRUITING

Investigational Site Number : 3560002

Mumbai, 400022, India

RECRUITING

Investigational Site Number : 3560001

Pune, 411004, India

RECRUITING

Investigational Site Number : 3800002

Florence, Firenze, 50134, Italy

RECRUITING

Investigational Site Number : 3800001

Milan, Milano, 20122, Italy

RECRUITING

Investigational Site Number : 3800003

Rozzano, Milano, 20089, Italy

RECRUITING

Investigational Site Number : 6160002

Wroclaw, Lower Silesian Voivodeship, 50-556, Poland

RECRUITING

Investigational Site Number : 6420001

Iași, 700309, Romania

RECRUITING

Investigational Site Number : 6420003

Timișoara, 300011, Romania

RECRUITING

Investigational Site Number : 7240001

Esplugues de Llobregat, Barcelona [Barcelona], 08950, Spain

RECRUITING

Investigational Site Number : 7240002

Madrid, 28046, Spain

RECRUITING

Investigational Site Number : 7240003

Zaragoza, 50009, Spain

RECRUITING

Investigational Site Number : 1580002

Taichung, 402, Taiwan

RECRUITING

Investigational Site Number : 1580001

Taipei, 100, Taiwan

RECRUITING

Investigational Site Number : 7920001

Istanbul, 34093, Turkey (Türkiye)

RECRUITING

Investigational Site Number : 7920002

Izmir, 35100, Turkey (Türkiye)

RECRUITING

Related Links

• EFC17905 Plain Language Results Summary
• EFC17905 (ATLAS-KIDS) website for potential participants

MeSH Terms

Conditions

Hemophilia A

Interventions

fitusiran

Condition Hierarchy (Ancestors)

Blood Coagulation Disorders, Inherited; Blood Coagulation Disorders; Hematologic Diseases; Hemic and Lymphatic Diseases; Coagulation Protein Disorders; Hemorrhagic Disorders; Genetic Diseases, Inborn; Congenital, Hereditary, and Neonatal Diseases and Abnormalities

Central Study Contacts

Trial Transparency email recommended (Toll free for US & Canada)

CONTACT

800-633-1610; Contact-US@sanofi.com

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: December 9, 2025
• First Posted: December 16, 2025
• Study Start: December 18, 2025
• Primary Completion (Estimated): August 4, 2029
• Study Completion (Estimated): December 30, 2031
• Last Updated: May 5, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will share

Locations

IN (2); TW (2); CA (1); IT (3); PL (1); US (4); BR (2); ES (3); RO (2); BE (2); TU (2)