Fitusiran

QFITLIA is a double-stranded siRNA that causes degradation of AT messenger RNA (mRNA) through RNA interference, reducing plasma AT levels.

• QFITLIA is indicated for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients aged 12 years and older with hemophilia A or B with or without factor VIII or IX inhibitors. QFITLIA is an antithrombin-directed small interfering ribonucleic acid indicated for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients aged 12 years and older with hemophilia A or B with or without factor VIII or IX inhibitors.

• None.contraindicated

For subcutaneous use only. Starting dose: 50 mg once every 2 months ( 2.1 ). Monitor AT activity using an FDA-cleared test. Maintain AT activity between 15–35% by adjusting the dose and/or frequency of administration ( 2.2 ). See Full Prescribing Information for important preparation and administration instructions ( 2.4 ). 2.1 Recommended Dosage For subcutaneous use only. Use of QFITLIA is recommended under the supervision of a healthcare professional experienced in the treatment of hemophilia or bleeding disorders. Measure AT activity prior to initiation of QFITLIA. Do not initiate QFITLIA dosing if AT activity is <60%. Monitor AT activity using an FDA-cleared test. Information on FDA-cleared tests for AT activity is available at http://www.fda.gov/CompanionDiagnostics. After QFITLIA is initiated, patients may continue their prior clotting factor concentrates (CFC) or bypassing agent (BPA) prophylaxis for the first 7 days of treatment. Discontinue CFC or BPA prophylaxis no later than 7 days after the initial dose of QFITLIA. The starting dose of QFITLIA is 50 mg once subcutaneously every two months. Adjust the dose and/or dosing interval, if needed, to maintain AT activity between 15–35% [see Boxed Warning , Dosage and Administration (2.2) and Warnings and Precautions (5.1) ] . 2.2 Dosage Modification Measure AT activity using an FDA-cleared test at Weeks 4 (Month 1), 12 (Month 3), 20 (Month 5) and 24 (Month 6) following the starting dose and after any dose modification. If any AT activity is <15%, a dose reduction is required.

Hepatotoxicity: Obtain liver tests at baseline and then monthly for at least 6 months after initiating QFITLIA and after dose increases, and periodically thereafter. Liver test elevations may require QFITLIA interruption or discontinuation ( 5.3 ). 5.1 Thrombotic Events Serious thrombotic events have been reported in QFITLIA-treated patients. Thrombotic events were reported in 2.6% of patients receiving the 80 mg once monthly dose (2.3 events per 100 person-years), including a fatal event of cerebral venous sinus thrombosis. The 80 mg once monthly dose is not approved or recommended for use. Thrombotic events were reported in 1.4% of patients receiving QFITLIA prophylaxis using the antithrombin-based dose regimen (AT-DR) that targeted AT activity 15-35% (0.8 events per 100 person-years). Participants with established thrombophilia or a history of thrombosis were generally excluded from studies with QFITLIA. The risk of thrombosis is greater in patients with persistent AT activity <15%, with comorbidities that predispose to thrombosis, when bleed management guidelines are not followed in the post-operative setting, when there is an indwelling venous catheter, and with use of the 80 mg once monthly (non-AT-based) dose. Treatment of breakthrough bleeding episodes with CFC or BPA at a dose greater or more frequent than recommended may also increase thrombotic risk [see Dosage and Administration (2.3) ] .

The following clinically significant adverse reactions are described elsewhere in the labeling: Thrombotic Events [see Boxed Warning and Warnings and Precautions (5.1) ] Acute and Recurrent Gallbladder Disease [see Boxed Warning and Warnings and Precautions (5.2) ] Hepatotoxicity [see Warnings and Precautions (5.3) ] Common adverse reactions (incidence >10%) are viral infection, nasopharyngitis, and bacterial infection ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Genzyme Corporation 1-800-745-4447 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The pooled safety population described in the WARNINGS AND PRECAUTIONS reflect exposure to QFITLIA as fixed doses and AT-DR (N=335). The safety of the QFITLIA AT-DR was assessed in 286 adult and pediatric male patients with hemophilia A or B with or without inhibitors [see Clinical Studies (14) ] . Among patients who received the AT-DR, 93% were exposed for 6 months or longer and 83% were exposed for 12 months or longer. The median duration of exposure across the studies was 674 days (with a maximum of 896 days). Serious adverse reactions occurred in 4/286 (1.4%) patients who received the AT-DR, two of whom had serious adverse reactions of cholecystitis.

Avoid use in patients with established hepatic impairment (Child-Pugh Class A, B and C) ( 8.6 ). To report SUSPECTED ADVERSE REACTIONS, contact Genzyme Corporation 1-800-745-4447 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 8.1 Pregnancy Risk Summary There are no available data on QFITLIA use in pregnant women to evaluate for a drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes. Reproduction studies in pregnant animals have not been conducted with fitusiran. It is not known whether QFITLIA can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. QFITLIA should be used during pregnancy only if the potential benefit justifies the potential risks, including those to the fetus. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2–4% and 15–20%, respectively. 8.2 Lactation Risk Summary There are no data on the presence of fitusiran or its metabolite in human milk, the effects on the breastfed child, or the effects on milk production. It is not known whether QFITLIA is safe for use during breastfeeding.

Metabolism

The pharmacokinetic (PK) properties of fitusiran were evaluated following administration of QFITLIA in patients with hemophilia A or B, with or without inhibitors as summarized in Table 4. QFITLIA PD is driven by liver PK rather than plasma PK.

• Mar 28, 2025NDANDA219019Genzyme Corp

1. 1Haemorrhage828%
2. 2Arthralgia414%
3. 3Chest Pain414%
4. 4Off Label Use310%
5. 5Abdominal Pain Lower26.9%
6. 6Condition Aggravated26.9%
7. 7Contusion26.9%
8. 8Fall26.9%
9. 9Spontaneous Haemorrhage26.9%
10. 10Abdominal Distension13.4%
11. 11Abdominal Pain13.4%
12. 12Abdominal Pain Upper13.4%
13. 13Accidental Exposure To Product13.4%
14. 14Antithrombin Iii Decreased13.4%
15. 15Arteriosclerosis Coronary Artery13.4%

The 9 most recently updated of 9 ClinicalTrials.gov registrations naming Fitusiran as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• A Study to Test a Medicine (Fitusiran) for Preventing Bleeds in People With Severe Hemophilia Who Previously Received Preventive Treatment With Emicizumab
  Recruiting · Phase 4 · Interventional · 20 enrolled · Sanofi
  NCT06145373updated 2026-06-02
• 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
  Recruiting · Phase 3 · Interventional · 85 enrolled · Sanofi
  NCT07285460updated 2026-05-26
• A Study to Test a Medicine (Fitusiran) Injected Under the Skin for Preventing Bleeding Episodes in Male Adolescent or Adult Participants With Severe Hemophilia
  Active not recruiting · Phase 3 · Interventional · 91 enrolled · Sanofi
  NCT05662319updated 2026-02-04
• 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
  Active not recruiting · Phase 3 · Interventional · 281 enrolled · Genzyme, a Sanofi Company
  NCT03754790updated 2025-12-17
• Fitusiran Prophylaxis in Male Pediatric Subjects Aged 1 to Less Than 12 Years With Hemophilia A or B
  Active not recruiting · Phase 3 · Interventional · 32 enrolled · Genzyme, a Sanofi Company
  NCT03974113updated 2025-08-08
• An Open-label Extension Study of an Investigational Drug, Fitusiran, in Patients With Moderate or Severe Hemophilia A or B
  Completed · Phase 1 · Phase 2 · Interventional · 34 enrolled · Genzyme, a Sanofi Company
  NCT02554773updated 2024-06-05
• A Study of Fitusiran in Severe Hemophilia A and B Patients Previously Receiving Factor or Bypassing Agent Prophylaxis
  Completed · Phase 3 · Interventional · 80 enrolled · Genzyme, a Sanofi Company
  NCT03549871updated 2023-02-06
• A Study of Fitusiran (ALN-AT3SC) in Severe Hemophilia A and B Patients Without Inhibitors
  Completed · Phase 3 · Interventional · 120 enrolled · Genzyme, a Sanofi Company
  NCT03417245updated 2022-03-28
• A Study of Fitusiran (ALN-AT3SC) in Severe Hemophilia A and B Patients With Inhibitors
  Completed · Phase 3 · Interventional · 60 enrolled · Genzyme, a Sanofi Company
  NCT03417102updated 2022-03-28

Frequently asked questions

How does Fitusiran work?

QFITLIA is a double-stranded siRNA that causes degradation of AT messenger RNA (mRNA) through RNA interference, reducing plasma AT levels.

What is Fitusiran used for?

According to FDA labeling, Fitusiran carries indications including: QFITLIA is indicated for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients aged 12 years and older with hemophilia A or B with or without factor VIII or IX inhibitors. QFITLIA is an antithrombin-directed small interfering ribonucleic acid indicated for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients aged 12 years and older with hemophilia A or B with or without factor VIII or IX inhibitors.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Fitusiran?

Fitusiran is classified as Other systemic hemostatics, Antithrombin-directed RNA Interaction, Small Interfering RNA, Decreased Protein Synthesis, Decreased RNA Integrity, Increased RNA Degradation.

What are the brand names for Fitusiran?

Fitusiran is marketed under brand names including Qfitlia.

What are the contraindications for Fitusiran?

Fitusiran labeling lists contraindications including: None.. Always consult the full prescribing information and a clinician.