Drug Trials Snapshots: QFITLIA

QFITLIA (fitusiran) 
kew-fit-lee-ah
Genzyme Corporation
Original Approval date: March 28, 2025 

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DRUG TRIALS SNAPSHOT SUMMARY:

What is the drug for?

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. 

Hemophilia A and hemophilia B are inherited blood-clotting disorders that affect primarily males. Hemophilia is caused by a missing or abnormal clotting protein (factor VIII in hemophilia A or factor IX in hemophilia B) that make it more difficult to stop bleeding. Many patients with hemophilia A or B will develop an immune response known as factor VIII or factor IX inhibitors or antibodies.

How is this drug used?

QFITLIA is a preventative (prophylactic) treatment injected under the skin (subcutaneous injection), with initial dosing of 50 mg every two months. The dose should be adjusted, if needed, to maintain antithrombin activity levels between 15% to 35%. 

Who participated in the clinical trials?

The FDA approved QFITLIA based on evidence from a clinical trial, ATLAS-OLE (NCT03754790) which included 177 adult and pediatric patients 12 years of age and older with hemophilia A (congenital factor VIII deficiency) without factor VIII inhibitors (n=93), hemophilia A with factor VIII inhibitors (n=38), hemophilia B (congenital factor IX deficiency) without factor IX inhibitors (n=27), and hemophilia B with factor IX inhibitors (n=19). The trial was conducted at 79 sites in 31 countries including the United States, Canada, Colombia, Mexico, Bulgaria, Denmark, France, Germany, Hungary, Italy, Spain, Turkey, Ukraine, the United Kingdom, Ireland, Switzerland, Russia, Croatia, Poland, China, India, Japan, South Korea, Malaysia, Taiwan, Hong Kong, Thailand, Singapore, Australia, South Africa, and Israel. There were 13 patients from the United States. 

How were the trials designed?

ATLAS-OLE enrolled patients 12 years of age and older, with hemophilia A or hemophilia B, with or without inhibitors, who had previously participated in ATLAS trials (ATLAS-INH, ATLAS-A/B, ATLAS-PPX). ATLAS-OLE was an open label extension trial where QFITLIA dose followed the antithrombin dose regimen (AT-DR). In the AT-DR, the QFITLIA starting dose was 50 mg every two months, and dosing was individually adjusted based on anti-thrombin activity targeted to 15% to 35%. The efficacy of QFITLIA AT-DR in ATLAS-OLE was evaluated for a duration of seven months.

The benefit of QFITLIA was assessed in ATLAS-OLE by comparing the number of bleeding episodes that required treatment when receiving QFITLIA compared to the number of bleeding episodes that required treatment when receiving factor or bypassing agents, either on-demand or prophylaxis, during the ATLAS-INH, ATLAS-A/B, or ATLAS-PPX trials. 

DEMOGRAPHICS SNAPSHOT

All patients enrolled in the ATLAS-OLE trial were male.

Figure 1 summarizes how many patients by race were enrolled in the ATLAS-OLE trial used to evaluate the efficacy of QFITLIA AT-DR.

Figure 1. Baseline Demographics by Race 

_{Source: Adapted from FDA Review}

Figure 2 summarizes how many patients by age were enrolled in the ATLAS-OLE trial used to evaluate the efficacy of QFITLIA AT-DR.

Figure 2. Baseline Demographics by Age 

_{Source: Adapted from FDA Review}

Figure 3 summarizes how many patients by ethnicity were enrolled in the ATLAS-OLE trial used to evaluate the efficacy of QFITLIA AT-DR.

Figure 3. Baseline Demographics by Ethnicity 
 

_{Source: Adapted from FDA Review}

What are the benefits of this drug? 

Patients with hemophilia A or B with inhibitors treated with QFITLIA had a 73% reduction in bleeding events (estimated per year) compared to when they were receiving bypassing agents on-demand (estimated per year).
Patients with hemophilia A or B without inhibitors had a 71% reduction in bleeding events (estimated per year) compared to when they were receiving factor on-demand (estimated per year).

Were there any differences in how well the drug worked in clinical trials among sex, race, and age? 

• Sex: All patients were males; therefore, differences in how QFITLIA worked between females and males could not be determined.
• Race: The observed effect of QFITLIA was similar for Asian or White patients. The number of patients in other races was limited; therefore, differences in how QFITLIA worked in other races could not be determined. 
• Age: There were few participants <18 years of age and >65 years of age; therefore, differences in how QFITLIA worked among age groups could not be determined.

What are the possible side effects?

The safety of QFITLIA was evaluated in 286 adolescent and adult patients with severe hemophilia A or B with and without inhibitors who enrolled in the ATLAS-INH, ALTAS-A/B, and ATLAS-PPX trials. Patients received QFITLIA prophylaxis 50 mg dose every other month and had dose adjustments to target antithrombin levels 15% to 35% (AT-DR). Among patients receiving QFITLIA AT-DR, 93% were exposed for six months or longer and 83% were exposed for at least one year.

QFITLIA can cause thrombotic events (blood clots), acute and recurrent gallbladder disease, and hepatotoxicity (elevated liver enzymes).

The most common adverse reactions (≥5% of participants) are viral infection, nasopharyngitis, bacterial infection, hepatic injury, arthralgia, prothrombin fragment 1.2 increased, injection site reaction, headache, and cough.

Were there any differences in side effects among sex, race, and age?

• Sex: All participants were male; therefore, differences in side effects between sexes could not be determined.
• Race: The majority of participants were Asian (59%) and White (36%). The occurrence of side effects was similar between White and Asian. The number of participants in other races was limited; therefore, differences in side effects among races could not be determined.
• Age: Almost all participants were younger than 65 years of age; therefore, differences in side effects in participants younger and older than 65 years of age could not be determined.

GLOSSARY

CLINICAL TRIAL: Voluntary research studies conducted in people and designed to answer specific questions about the safety or effectiveness of drugs, vaccines, other therapies, or new ways of using existing treatments.

COMPARATOR: A previously available treatment or placebo used in clinical trials that is compared to the actual drug being tested.

EFFICACY: How well the drug achieves the desired response when it is taken as described in a controlled clinical setting, such as during a clinical trial.

PLACEBO: An inactive substance or “sugar pill” that looks the same as, and is given the same way as, an active drug or treatment being tested. The effects of the active drug or treatment are compared to the effects of the placebo.

SUBGROUP: A subset of the population studied in a clinical trial. Demographic subsets include sex, race, and age groups.

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