HemophiliaPhase 3ATLAS-KIDSNCT07285460
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
A Phase 3 study testing Fitusiran, Clotting factor concentrates (CFC) or bypassing agents (BPA) and Antithrombin concentrate (ATIIIC) in people with Hemophilia, run by Sanofi at 41 sites in 13 countries.
Trial 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. Read more about this study
- Who is it for?
- Ages 1 year to 11 years, men only
- Conditions the study is for
- Hemophilia
- What is being tested?
- Fitusiran, Clotting factor concentrates (CFC) or bypassing agents (BPA) and Antithrombin concentrate (ATIIIC)
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 85 participants
- Where
- 41 sitesin 13 countries
- Study dates
- 18 Dec 2025to 30 Dec 2031
- Phase
- Phase 3
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 1 year to 11 years
- Men only
- No healthy volunteers
- Child
Who may be able to join
- 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:
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- 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.
- Capable of giving signed informed consent/assent. A signed written informed consent must be obtained from parent(s)/legal guardian (hereafter referred to as the "parent"), as well as a written or oral assent obtained from participant, per local and national requirements.
Who cannot join
- 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.
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- 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.
- AT activity <60% at screening, as determined by central laboratory analysis.
- Co-existing thrombophilic disorder.
- Presence of an active Hepatitis C virus infection
- Presence of acute hepatitis A or Hepatitis E virus infection.
- Presence of acute or chronic hepatitis B virus infection.
- Platelet count ≤100 000/μL.
- Presence of acute infection at screening.
- Human immunodeficiency virus (HIV) positive with a CD4 count of <400 cells/μL.
- Estimated glomerular filtration rate ≤45 mL/min/1.73 m2 (using the Schwartz formula).
- The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.
Trial locations and contacts
41 sites in 13 countries. Contact the study team or a site near you to ask about taking part.
Trial Transparency email recommended (Toll free for US & Canada) contact
41 sites in 13 countries
United States10 sites, 10 recruiting
- Recruiting
University of Michigan Health System - Ann Arbor- Site Number : 8400003
Ann Arbor, Michigan, 48109
- Recruiting
University of Texas - Southwestern Medical Center- Site Number : 8400015
Dallas, Texas, 75390
- Recruiting
Hackensack Meridian Health - Hackensack University Medical Center- Site Number : 8400008
Hackensack, New Jersey, 07601
- Recruiting
Cure 4 The Kids Foundation- Site Number : 8400001
Las Vegas, Nevada, 89147
- Recruiting
The Luskin Orthopaedic Institute for Children- Site Number : 8400013
Los Angeles, California, 90007
- Recruiting
Children's Hospital Los Angeles- Site Number : 8400002
Los Angeles, California, 90027
- Recruiting
University of Miami Hospital- Site Number : 8400005
Miami, Florida, 33136
- Recruiting
Tulane University School of Medicine- Site Number : 8400026
New Orleans, Louisiana, 70112
- Recruiting
The Center for Inherited Blood Disorders- Site Number : 8400009
Orange, California, 92868
Suzette David, 714-221-1224
Vanessa Salinas
- Recruiting
UCLA Medical Center - Harbor- Site Number : 8400011
Torrance, California, 90509
India4 sites, 4 recruiting
- Recruiting
Investigational Site Number : 3560004
Bengaluru, 560034
- Recruiting
Investigational Site Number : 3560002
Mumbai, 400022
- Recruiting
Investigational Site Number : 3560001
Pune, 411004
- Recruiting
Investigational Site Number : 3560003
Vellore, 632004
Brazil3 sites, 3 recruiting
- Recruiting
Universidade Estadual de Campinas (UNICAMP)- Site Number : 0760001
Campinas, São Paulo, 13084-225
- Recruiting
Hospital das Clinicas da Faculdade de Medicina de Ribeirao Preto- Site Number : 0760003
Ribeirão Preto, São Paulo, 14049-900
- Recruiting
Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo- Site Number : 0760004
São Paulo, 05403-000
Canada3 sites, 3 recruiting
- Recruiting
Investigational Site Number : 1240001
Hamilton, Ontario, L8N 3Z5
- Recruiting
Investigational Site Number : 1240003
Montreal, Quebec, H3T 1C5
- Recruiting
Investigational Site Number : 1240005
Toronto, Ontario, M5G 1X8
Italy3 sites, 3 recruiting
- Recruiting
Investigational Site Number : 3800002
Florence, Firenze, 50134
- Recruiting
Investigational Site Number : 3800001
Milan, Milano, 20122
- Recruiting
Investigational Site Number : 3800003
Rozzano, Milano, 20089
Poland3 sites, 3 recruiting
- Recruiting
Investigational Site Number : 6160003
Poznan, Greater Poland Voivodeship, 60-572
- Recruiting
Investigational Site Number : 6160001
Warsaw, Masovian Voivodeship, 02-091
- Recruiting
Klinika Transplantacji Szpiku, Onkologii i Hematologii Dziecięcej - Uniwersytecki Szpital Kliniczny im. Jana Mikulicza-Radeckiego we Wrocławiu-Site Number: 6160002
Wroclaw, Lower Silesian Voivodeship, 50-556
Marta Hetman, +48 530060737, martha.hetman@gmail.com
Elzbieta Latos-Grazynska
Spain3 sites, 3 recruiting
- Recruiting
Investigational Site Number : 7240001
Esplugues de Llobregat, Barcelona [Barcelona], 08950
- Recruiting
Investigational Site Number : 7240002
Madrid, Madrid, Comunidad de, 28046
- Recruiting
Investigational Site Number : 7240003
Zaragoza, Aragon, 50009
Belgium2 sites, 2 recruiting
- Recruiting
Investigational Site Number : 0560002
Brussels, 1020
- Recruiting
Investigational Site Number : 0560001
Brussels, 1200
China2 sites, 2 recruiting
- Recruiting
Investigational Site Number : 1560001
Beijing, 100045
- Recruiting
Investigational Site Number : 1560002
Wuhan, 430030
Romania2 sites, 2 recruiting
- Recruiting
Spitalul Clinic De Urgenta Pentru Copii Sfanta Maria Iasi, Department: St. Mary Children's Emergency Clinical Hospital-Site Number : 6420001
Iași, 700309
Ingrith Miron, 0372 309 695, spitalcopii@sfmaria-iasi.com
Ingrith Miron
- Recruiting
Spitalul Clinic De Urgenta pentru Copii "Louis Turcanu"-Site Number : 6420003
Timișoara, 300011
Andreea Pascalau, pascalau_andreea@yahoo.com
Cristina Emilia Ursu
Saudi Arabia2 sites, 2 recruiting
- Recruiting
Investigational Site Number : 6820002
Dammam, 34212
- Recruiting
Investigational Site Number : 6820001
Riyadh, 12746
Taiwan2 sites, 2 recruiting
- Recruiting
Department of pediatrics, Chung Shan University Hospital-Site Number : 1580002
Taichung, 40201
Shu-Hui Kao, shuhui540727@gmail.com
TeFu Weng
- Recruiting
The division of Hematology, National Taiwan University Hospital-Site Number : 1580001
Taipei City, Taipei, 100
Yu-Shan Huang, yushanh0211@gmail.com
Sheng-Chieh Chou
Turkey (Türkiye)2 sites, 2 recruiting
- Recruiting
Investigational Site Number : 7920001
Istanbul, 34093
- Recruiting
Investigational Site Number : 7920002
Izmir, 35100
About this study
Official title: An Open-label, Parallel, Phase 3, Two-arm 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 With or Without Inhibitory Antibodies to Factors VIII or IX
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:
Read more
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.
Read the detailed description
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
- Being tested
- Fitusiran, Clotting factor concentrates (CFC) or bypassing agents (BPA), Antithrombin concentrate (ATIIIC)
- Medical subject headings
- Hemophilia A
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
FitusiranDrug
Also called SAR439774, Qfitlia™
Pharmaceutical form: solution for injection in PBS Route of administration: subcutaneous
Clotting factor concentrates (CFC) or bypassing agents (BPA)Biological
Pharmaceutical form: solution for injection Route of administration: intravenous injection
Antithrombin concentrate (ATIIIC)Biological
Pharmaceutical form: solution for injection Route of administration: intravenous injection
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: 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. Receives: Drug: Fitusiran; Biological: Clotting factor concentrates (CFC) or bypassing agents (BPA); Biological: Antithrombin concentrate (ATIIIC) |
What is being measured
The primary outcome is the main question the study is designed to answer.
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
Measured: 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
A spontaneous bleeding episode is a bleeding event that occurs for no apparent or known reason, particularly into the joints, muscles, and soft tissues
Measured: 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
A joint bleeding episode is characterized by an unusual sensation in the joint ("aura") in combination with 1) increasing swelling or warmth over the skin over the joint, 2) increasing pain, or 3) progressive loss of range of motion or difficulty in using the limb as compared with baseline
Measured: 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
A bleeding episode is defined as any occurrence of hemorrhage that requires administration of CFCs or BPAs
Measured: Day 1 to Day 1121
ABR in the fitusiran treatment period (60 weeks) for rolled-over participants
A bleeding episode is defined as any occurrence of hemorrhage that requires administration of CFCs or BPAs
Measured: Day 1 to Day 421
Change in physical activity
Change in physical activity as measured via the PROMIS questionnaire
Measured: From Day 1 to Day 421; From Week -24 to Day -1
Change in pain intensity
Change in pain intensity as measured via the PROMIS questionnaire
Measured: From Day 1 to Day 421; From Week -24 to Day -1
Change in HRQoL
Change in HRQoL as measured by the EuroQoL 5-dimension questionnaire
Measured: From Day 1 to Day 421; From Week -24 to Day -1
Incidence, severity, seriousness, and relatedness of adverse events (AEs)
All AEs are collected from the signing of the informed consent form (ICF) until last AT follow up visit
Measured: Date of signed ICF (Day -228 to Day -169) until last AT follow-up visit (Day 1121 + approximately 24 weeks)
Change in total score and domain scores
Change in total score and domain scores is assessed by the Hemophilia Joint Health Score
Measured: From Day 1 to Day 421; From Week -24 to Day -1
Target joints resolution
Target joints resolution assessed per ISTH criteria
Measured: At Day 421
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Dec 2025
- Study start18 Dec 2025
- Primary completion4 Aug 2029 (estimated)
- Study completion30 Dec 2031 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HemophiliaStudies of the same condition, open and under way.
- More trials run by SanofiThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 85 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Sanofi
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07285460
- Sponsor's protocol ID
- EFC17905
- Other IDs
- U1111-1280-7028, 2025-521858-42, 2025
- Acronym
- ATLAS-KIDS
- Status last verified
- Oct 2026
- First submitted
- 9 Dec 2025
- Last updated
- 19 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org