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Fitusiran

Phase 3

Hemophilia | Small molecule | Hematology |Sanofi|Last Updated: Sep 8, 2026

Target and mechanism

Molecular targetSERPINC1
Target classRnai Inhibitor
ModalitySmall molecule

Success Probability

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Market & Valuation

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Trial Design

CONTROLLEDDMC
Total Trials5
Total Enrollment569

FDA Designations

No designations recorded

Clinical trial landscape

Fitusiran · 8 trials · 3 indications

Phase 3 7Phase 1 1
NCT07285460A Study to Investigate the Efficacy and Safety of Fitusiran Prophylaxis in Male Participants Aged 1 to Less Than 12 Years With Hemophilia A or BHemophilia
RECRUITING85 Analytics
NCT05662319A Study to Test a Medicine (Fitusiran) Injected Under the Skin for Preventing Bleeding Episodes in Male Adolescent or Adult Participants With Severe HemophiliaHemophilia
ACTIVE NOT_RECRUITING91 Analytics
NCT03974113Fitusiran Prophylaxis in Male Pediatric Subjects Aged 1 to Less Than 12 Years With Hemophilia A or BHemophilia
COMPLETED32 Analytics
NCT03754790Long-term Safety and Efficacy Study of Fitusiran in Patients With Hemophilia A or B, With or Without Inhibitory Antibodies to Factor VIII or IXHemophilia
ACTIVE NOT_RECRUITING281 Analytics
NCT03549871A Study of Fitusiran in Severe Hemophilia A and B Patients Previously Receiving Factor or Bypassing Agent ProphylaxisHemophilia
COMPLETED80 Analytics
NCT03417245A Study of Fitusiran (ALN-AT3SC) in Severe Hemophilia A and B Patients Without InhibitorsHemophilia A
COMPLETED120 Analytics
NCT03417102A Study of Fitusiran (ALN-AT3SC) in Severe Hemophilia A and B Patients With InhibitorsHemophilia A
COMPLETED60 Analytics
PHASE3RECRUITING
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
HemophiliaUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
A Study to Test a Medicine (Fitusiran) Injected Under the Skin for Preventing Bleeding Episodes in Male Adolescent or Adult Participants With Severe Hemophilia
HemophiliaUnlock trial analytics
PHASE3COMPLETED
Fitusiran Prophylaxis in Male Pediatric Subjects Aged 1 to Less Than 12 Years With Hemophilia A or B
HemophiliaUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
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
HemophiliaUnlock trial analytics
PHASE3COMPLETED
A Study of Fitusiran in Severe Hemophilia A and B Patients Previously Receiving Factor or Bypassing Agent Prophylaxis
HemophiliaUnlock trial analytics
PHASE3COMPLETED
A Study of Fitusiran (ALN-AT3SC) in Severe Hemophilia A and B Patients Without Inhibitors
Hemophilia AUnlock trial analytics
PHASE3COMPLETED
A Study of Fitusiran (ALN-AT3SC) in Severe Hemophilia A and B Patients With Inhibitors
Hemophilia AUnlock trial analytics

Study Endpoints

Primary Endpoints

Annualized treated bleeding rate (ABR) 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)

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

Annualized bleeding rate (ABR) in the fitusiran primary efficacy period
Day 169 to Day 505 (since the first dose of fitusiran)

A bleeding episode is defined as any occurrence of hemorrhage that requires administration of CFCs or BPAs, e.g., hemarthrosis, muscle, or mucosal bleeding.

Plasma antithrombin (AT) activity levels
Day 1 to the AT analysis time point at the optimal therapeutic dose (approximately 256 weeks)

Characterize the AT activity at the optimal therapeutic dose

Number of participants with treatment emergent adverse events (TEAEs)
from study baseline (day 1) up to maximum 88 months

The number of participants experiencing any TEAEs, serious TEAEs, discontinuation due to TEAEs and death will be reported

Estimated Annualized Bleeding Rate (ABR)
Factor/BPA prophylaxis period: Day -168 to Day -1 or up to last day of bleeding follow up (any day up to Day -1); 6-month fitusiran efficacy period: Day 29 to Day 190 or up to last day of bleeding follow up (any day up to Day 190), whichever was earliest

Bleeding episodes (BE): any occurrence of hemorrhage might require administration of factor/BPA. BE start time: time at which 1st BE symptoms develop; bleeding/any symptoms at same location occurred within 72 hours of last injection used to treat BE at that location was considered part of original BE and counted as 1 BE towards ABR. Bleeding began after 72 hours of last injection at that location was considered as a new event. ABR = total number of qualifying BE/total number of days in the respective period\*365.25. Estimated data were derived by using repeated measures negative binomial (NB) regression model.

Observed Annualized Bleeding Rate (ABR)
Factor/BPA prophylaxis period: Day -168 to Day -1 or up to last day of bleeding follow up (any day up to Day -1); 6-month fitusiran efficacy period: Day 29 to Day 190 or up to last day of bleeding follow up (any day up to Day 190), whichever was earliest

A bleeding episode (BE): any occurrence of hemorrhage might require administration of factor/BPA. BE start time: time at which 1st BE symptoms develop; bleeding/any symptoms at same location that occurred within 72 hours of last injection used to treat BE at that location was considered a part of original BE and counted as 1 BE towards ABR. Any bleeding that began after 72 hours of last injection at that location was considered as a new event. ABR = total number of qualifying BE/number of days in the respective period \*365.25.

Estimated Annualized Bleeding Rate (ABR) for Treated Bleeds During the Efficacy Period
From Day 29 up to Day 246 or up to the last day of bleeding follow up (any day up to Day 246), whichever was the earliest

ABR for a participant during efficacy period (EP) was defined as annualized number of bleeding episodes during EP annualized to a 1-year interval of time. Treated Bleeding episode: any occurrence of hemorrhage that required administration of by-passing agents (BPA) or factor. It started from first sign of a bleed and ended no more than 72 hours after last treatment for bleed, within which any symptoms of bleeding at same location or injections less than or equal to (\<=) 72 hours apart were considered the same bleeding episode. EP was defined as time duration starting from Day 29 when antithrombin (AT) lowering capacity of fitusiran had achieved therapeutic target range to the earliest of Day 246 or last day of bleeding follow up (maximum duration of EP: from Day 29 to Day 246). This outcome measure (OM) presents estimated results (i.e., results received by applying negative binomial \[NB\] regression model on data collected during EP).

Observed Annualized Bleeding Rate (ABR) for Treated Bleeds During the Efficacy Period
From Day 29 up to Day 246 or up to the last day of bleeding follow up (any day up to Day 246), whichever was the earliest

ABR for a participant during EP was defined as annualized number of bleeding episodes during EP annualized to a 1-year interval of time. ABR= number of bleeding episodes during EP divided by total number of days during EP\*365.25. A bleeding episode was defined as any occurrence of hemorrhage that required administration of BPA or factor. It started from the first sign of a bleed and ended no more than 72 hours after the last treatment for the bleed, within which any symptoms of bleeding at the same location or injections \<=72 hours apart were considered the same bleeding episode. EP was defined as time duration starting from Day 29 when the AT lowering capacity of fitusiran had achieved therapeutic target range to the earliest of Day 246 or the last day of bleeding follow up (maximum duration of EP: from Day 29 to Day 246). This OM presents observed results (i.e., descriptive statistics values based on the data collected during EP).

Number of Participants With Treatment Emergent Adverse Events (TEAEs) and Treatment Emergent Serious Adverse Events (SAEs)
From first dose of study drug (Day 1) up to end of the study (SAS 1: up to 76 months and SAS 2: up to 40 months)

An adverse event (AE) is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and which does not necessarily have to have a causal relationship with the treatment. An SAE is any untoward medical occurrence that results: death or life-threatening or inpatient hospitalization or prolongation of existing hospitalization or persistent or significant disability or congenital anomaly or medically important event. All AEs collected in LTE14762 were considered TEAE because all participants received dose in the parent study. AEs of special interest (AESI) are alanine aminotransferase (ALT) or aspartate aminotransferase (AST) elevations \>3× upper limit of normal (ULN) or suspected or confirmed thromboembolic events or severe or serious injection site reactions or systemic injection associated reactions or cholecystitis or cholelithiasis.

Number of Participants With Potentially Clinically Significant Abnormality (PCSA): Hematology
From first dose of study drug (Day 1) up to end of the study (SAS 1: up to 76 months and SAS 2: up to 40 months)

Blood samples were collected to determine the hematology laboratory significant abnormalities. Here, DFB = decrease from baseline, NB = non-black, and B = black.

Number of Participants With Potentially Clinically Significant Abnormality: Clinical Chemistry
From first dose of study drug (Day 1) up to end of the study (SAS 1: up to 76 months and SAS 2: up to 40 months)

Blood samples were collected to determine the clinical chemistry laboratory abnormalities. Here, mmol/L = millimoles per liter, LLN = lower limit of normal, mg/L = milligram per liter, umol/L = micromoles per liter, mL/min = milliliter per minute, m\^2 = meter square, CB = conjugated bilirubin, and DB = direct bilirubin.

Number of Participants With Potentially Clinically Significant Abnormality: Urinalysis
From first dose of study drug (Day 1) up to end of the study (SAS 1: up to 76 months and SAS 2: up to 40 months)

Urine samples collected to determine the significant abnormalities in urine.

Number of Participants With Potentially Clinically Significant Abnormality: Vital Signs
From first dose of study drug (Day 1) up to end of the study (SAS 1: up to 76 months and SAS 2: up to 40 months)

Participants vital signs were examined to determine the abnormalities. Vital signs included weight, supine systolic blood pressure (SSBP) and supine diastolic blood pressure (SDBP). Here, mmHg = millimeter of mercury, and IFB = increase from baseline.

Number of Participants With Potentially Clinically Significant Abnormality: Electrocardiogram (ECG)
From first dose of study drug (Day 1) up to end of the study (SAS 1: up to 76 months and SAS 2: up to 40 months)

Standard 12-lead ECGs were recorded after at least 15 minutes in the supine position using an electrocardiographic device. The following were assessed: heart rate, rhythm, interval between the peaks of successive QRS complexes (RR), interval from the beginning of the P wave until the beginning of the QRS complex (PR), interval from start of the Q wave to the end of the S wave (QRS), interval between the start of the Q wave and the end of the T wave (QT), QT interval corrected for heart rate (QTc) automatic correction evaluation, QRS axis, left ventricular hypertrophy criteria, right ventricular hypertrophy criteria, repolarization charges, and overall cardiac impression for each participant. Here, msec = milliseconds.

Number of Participants With Potentially Clinically Significant Abnormality: Physical Examination
From first dose of study drug (Day 1) up to end of the study (SAS 1: up to 76 months and SAS 2: up to 40 months)

Physical examination included, at a minimum, an assessment of the participant's general appearance; skin; head, eyes, ears, nose, and throat; examinations of lymph nodes, abdomen, extremities/joints, neurological and mental status; heart and respiratory auscultation; peripheral arterial pulse; and pupil, knee, achilles, and plantar reflexes.

Secondary Endpoints

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
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Study Design & Arms

AllocationNA
MaskingNONE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Fitusiran-naïve armEXPERIMENTALParticipants 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.
EFC15647 roll-over armEXPERIMENTALParticipants 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.
All participantsEXPERIMENTALIn standard of care (SOC) period, participants will receive on-demand or prophylactic treatment with clotting factor concentrates (CFCs) or bypassing agents (BPAs) for 6 months (from Day -168 to Day -1). In fitusiran treatment period, participants will receive subcutaneous fitusiran prophylaxis once every other month (Q2M) or once monthly (QM) for 36 months (from Day 1 to Day 1009). In case of bleeding events participants will receive IV CFCs or BPAs. Participants may receive Antithrombin concentrate (ATIIIC) as rescue medicine. .
FitusiranEXPERIMENTALParticipants will receive a selected dose of fitusiran at regular intervals, as per study protocol
Factor On-demandEXPERIMENTALParticipants received on-demand factor concentrates (as needed, for episodic bleeding episodes, and not on a regular regimen intended to prevent spontaneous bleeding) per Investigator discretion for the treatment of breakthrough bleeding episodes from Day 1 up to a total of 9 months.
Fitusiran 80 mg ProphylaxisEXPERIMENTALParticipants received open-label fitusiran 80 milligram (mg) administered subcutaneously (SC) as prophylaxis once monthly from Day 1 up to a total of 9 months. Participants received on-demand factor concentrates (per investigator's discretion and within bleeding dosing guidelines) for the treatment of breakthrough bleeding episodes.
Bypassing Agents (BPA) On-demandACTIVE_COMPARATORParticipants received On-demand BPAs (use of these agents, as needed, for episodic bleeding episodes, and not on a regular regimen intended to prevent spontaneous bleeding) per Investigator discretion from Day 1 for treatment of breakthrough bleeding episodes, up to a total of 9 months.

Interventions

NameTypeDescription
FitusiranDRUGPharmaceutical form: solution for injection in PBS Route of administration: subcutaneous
Clotting factor concentrates (CFC) or bypassing agents (BPA)BIOLOGICALPharmaceutical form: solution for injection Route of administration: intravenous injection
Antithrombin concentrate (ATIIIC)BIOLOGICALPharmaceutical form: solution for injection Route of administration: intravenous injection
BPA prophylaxisDRUGPharmaceutical form: solution for injection Route of administration: Intravenous
Factor (FVIII or FIX) prophylaxisDRUGPharmaceutical form: solution for injection Route of administration: Intravenous
factor concentratesDRUGby intravenous (IV) injection
Bypassing agentsDRUGsolution for injection; by intravenous (IV) injection
Fitusiran (SAR439774)DRUGPharmaceutical form: solution for injection Route of administration : subcutaneous (sc)
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Eligibility Criteria

Age Range1 Year to 11 Years
SexMALE
Healthy VolunteersNo
Study Sites30

Inclusion Criteria: 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...

Countries:United StatesBelgiumBrazilCanadaChinaIndiaItalyPolandRomaniaSaudi ArabiaSpainTaiwanTurkey (Türkiye)FranceGermanyGreeceJapanMexicoSouth AfricaSouth KoreaAustraliaDenmarkHungaryIrelandIsraelMalaysiaUkraineUnited KingdomBulgariaRussiaSwitzerland
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Recent Changes (Last 90 Days)

HIGHSep 8, 2026NCT03974113Status: ACTIVE_NOT_RECRUITING → COMPLETED
HIGHSep 8, 2026NCT03974113Status: ACTIVE_NOT_RECRUITING → COMPLETED
LOWAug 17, 2026NCT07285460lastUpdatePostDate: changed
LOWAug 17, 2026NCT07285460lastUpdatePostDate: changed
LOWJun 25, 2026NCT07285460lastUpdatePostDate: changed
LOWJun 25, 2026NCT07285460lastUpdatePostDate: changed
LOWJun 25, 2026NCT07285460lastUpdatePostDate: changed
LOWJun 22, 2026NCT03974113Phase: PHASE3 → PHASE2
LOWJun 22, 2026NCT03974113Phase: PHASE3 → PHASE2

Frequently asked questions about Fitusiran

What is Fitusiran used for in hemophilia?

Fitusiran is an investigational small molecule being developed for the treatment of hemophilia, including hemophilia A. It is designed to prevent bleeding episodes in patients with hemophilia A or B, with or without inhibitory antibodies to factor VIII or IX. The drug is administered as a subcutaneous injection.

What does Fitusiran target?

Fitusiran targets SERPINC1, which encodes antithrombin, a protein that inhibits blood clotting. By reducing antithrombin production through RNA interference, Fitusiran aims to promote thrombin generation and restore hemostasis in patients with hemophilia. This mechanism is classified as an RNAi inhibitor approach.

Who makes Fitusiran?

Fitusiran is being developed by Sanofi, a global biopharmaceutical company listed on the stock exchange under the ticker symbol SNY. Sanofi is conducting clinical trials to evaluate the safety and efficacy of Fitusiran in patients with hemophilia.

What phase is Fitusiran in?

Fitusiran is currently in Phase 3 clinical development. It is an investigational drug and has not been approved by regulatory authorities. Several Phase 3 trials are ongoing or completed, including studies in severe hemophilia A and B patients and a long-term safety and efficacy study.

What clinical trials is Fitusiran in?

Fitusiran has been studied in multiple clinical trials, including NCT03549871 (Phase 3, completed), NCT03754790 (Phase 3, active), NCT03974113 (Phase 2, active), and NCT05662319 (Phase 3, active). These trials enroll male patients with hemophilia, ranging from pediatric to adult populations, across numerous countries.

Is Fitusiran the same as fitusiran sodium?

Fitusiran is sometimes referred to by its chemical name, fitusiran sodium, which is the salt form of the drug. In clinical trial records and scientific literature, the drug is commonly listed as fitusiran. Both names refer to the same investigational compound being developed by Sanofi for hemophilia.