This page shows what was measured, who it was measured in, and what that does not settle.
What Fitusiran does in the body
Used to prevent bleeding in haemophilia A or B.
Blood clotting is a tug of war between proteins that build clots and proteins that hold them back. Haemophilia takes away one of the builders. Instead of replacing it, fitusiran removes one of the holders — a liver protein called antithrombin — so the remaining builders can do more. It works whichever factor is missing, and it works even when the immune system has learned to destroy replacement factor. The danger is obvious from the mechanism: take the brake off too far and clots form where they should not, which is exactly what happened at the original dose.
What happened in people
Monthly treatment cut bleeding roughly tenfold, and two thirds of participants had no treated bleeds.
✓ Reviewed first-read answer
Where this came from
A person wrote this and a reviewer approved it against this exact record. It carries no effect size.
A reviewer approved this against this record. The reviewed-claim record carrying the exact population and effect size does not exist yet.
No source is stored against this line.
The limit that matters most
It was compared with treating bleeds as they happened, not with the usual preventive treatments.
Where it acts
Hepatocyte cytoplasm (liver)
Kind of result
The kind of result is not recorded
Supervision
Professional supervision is normally required. It is a prescription or clinician-administered medicine where it is approved.
What the registries record it as
The substance registry classes this as nucleicacid.
FDA substance registry · SV9W47ZLE1 · read 2026-08-29
Where each sentence above came from
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 122 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Messenger RNA
Messenger RNA is a working copy of one gene, carried to where proteins are built.
A picture of it, and where the picture fails
It is like a photocopy of one plan page, taken to the workshop.
Where that stops being true. A photocopy lasts. This copy is destroyed soon after use, on purpose.
What people get wrong. It is often thought to change the gene. It is a copy, and it does not alter the original.
A single-stranded transcript of a gene that ribosomes translate into a protein.
Small interfering RNA
A small interfering RNA is a short piece that makes a cell destroy one working copy.
A picture of it, and where the picture fails
It is like a note telling the workshop to shred one plan page.
Where that stops being true. A note is read once. This keeps working for months after one injection.
What people get wrong. It is often described as gene editing. It leaves the gene untouched.
A short double-stranded RNA that directs the RNA-induced silencing complex to cleave a complementary transcript.
Absolute difference
An absolute difference is how many more people in a hundred were affected.
A picture of it, and where the picture fails
It is like counting heads in two rooms of a hundred.
Where that stops being true. Heads are easy to count. Study results carry a margin of error too.
What people get wrong. It is confused with a percentage change, which can look far larger.
The arithmetic difference in event rates between arms.
Confidence interval
A confidence interval is the range the true answer is likely to sit in.
A picture of it, and where the picture fails
It is like a weather forecast giving a range rather than one number.
Where that stops being true. A forecast range covers tomorrow. This one covers what the study could resolve.
What people get wrong. The middle number is read as the answer. A range crossing zero means no change is still possible.
An interval estimate that would contain the true parameter in a stated proportion of repeated studies.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Mean annualised bleeding rate over the 9-month efficacy period
✓ The study showed what it set out to show
Who was studied
ATLAS-INH (NCT03417102)
How many people
57
Study design
Phase 3, open-label
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
P < 0.0001
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Increased alanine aminotransferase in 32% of the fitusiran safety population and none in the comparator arm; suspected or confirmed thromboembolic events in 2 of 38 participants (5%). The 80 mg monthly regimen used here is no longer approved.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. GalNAc-conjugated siRNA, subcutaneous prefilled pen or vial
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
ATLAS-INH (NCT03417102) · a recorded source, not a stored snapshot
Annualised bleeding rate, intention-to-treat
✓ The study showed what it set out to show
Who was studied
ATLAS-A/B (NCT03417245)
How many people
120
Study design
Phase 3, open-label
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
P < 0.0001 (rate ratio 0.101, 95% CI 0.064 to 0.159)
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Increased alanine aminotransferase in 23% of the fitusiran safety population. No treatment-related thrombosis or deaths in this trial, though thrombosis appeared elsewhere in the programme.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. GalNAc-conjugated siRNA, subcutaneous prefilled pen or vial
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
ATLAS-INH (NCT03417102) · a recorded source, not a stored snapshot
What we know
RNAWiki holds 2 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Fitusiran
What a person takes: GalNAc-conjugated siRNA, subcutaneous prefilled pen or vial.
The measurement behind this step
A 50 mg single-dose prefilled pen delivering 0.5 mL, and a 20 mg single-dose vial delivering 0.2 mL, for subcutaneous use under the supervision of a clinician experienced in bleeding disorders. Antithrombin activity is measured before initiation and monitored on an FDA-cleared test thereafter.
Getting in
Subcutaneous injection, dosed to a laboratory target
An injection under the skin every two months for most people, but the amount is set by a blood test rather than fixed, because the whole treatment is a balancing act.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
A triantennary GalNAc conjugate binds hepatocyte ASGPR. Uniquely among the drugs on this page, the label ties dosing to a pharmacodynamic measurement — antithrombin activity, maintained between 15% and 35% using an FDA-cleared assay — rather than to body weight or a fixed schedule.
Liver cells recognise the sugar tag and internalise the drug, holding a reservoir that releases over weeks.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
ASGPR-mediated endocytosis delivers the conjugate to the endosome; the receptor recycles and a fraction of the duplex escapes into the cytoplasm, with the endolysosomal depot supporting a two-monthly interval.
One strand is loaded into the cell's gene-silencing machinery; the other is discarded.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
The antisense strand loads into Argonaute 2 within RISC. No nucleotide sequence has been published for fitusiran, so this page records the chemistry from the label formula — twenty-one fluorines and six phosphorothioate sulfurs — and does not assert a sequence.
SERPINC1 messenger RNA is cut and antithrombin production falls
The complex destroys the instructions for antithrombin, the protein that restrains clotting. With less of it, the clotting that remains goes further.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Argonaute 2 cleaves SERPINC1 mRNA, reducing hepatic antithrombin synthesis. Antithrombin is the principal physiological inhibitor of thrombin and factor Xa, so lowering it increases thrombin generation independently of which coagulation factor is deficient — the reason the drug covers haemophilia A and B, with or without inhibitors.
Bleeding falls sharply. Push antithrombin too low and the balance tips the other way into dangerous clots, which is why the dose is chased to a target rather than fixed.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Increased thrombin generation reduced the annualised bleeding rate by 90.8% against on-demand bypassing agents and gave a rate ratio of 0.101 against on-demand factor. The therapeutic window is defined by antithrombin activity: persistent activity below 15% is a named risk factor for thrombosis in the boxed warning, and the target band is 15% to 35%.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
People aged 12 and over with haemophilia A or B, with or without inhibitors, on routine prophylaxis. Antithrombin activity is measured before and during treatment and the dose is adjusted to keep it inside a defined band.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What the label states about particular groups
On pediatric, the label states: “The safety and effectiveness of QFITLIA have not been established in pediatric patients below 12 years of age.”
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-30
On older people, the label states: “Clinical studies of QFITLIA did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.”
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-30
On people who are pregnant, the label states: “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.”
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-30
On people who are breastfeeding, the label states: “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.”
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-30
On people with reduced liver function, the label states: “Serum transaminase elevations have been observed in the clinical studies [see Warnings and Precautions (5.3) ] .”
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-30
Where the result stopped carrying
The 80 mg once-monthly regimen used throughout the phase 3 programme, now explicitly not approved or recommended in the FDA label
Dosing to a fixed amount at all: the regimen was rebuilt around a target antithrombin activity band of 15% to 35%
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Given by a clinician
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
GalNAc-conjugated siRNA, subcutaneous prefilled pen or vial
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Professional supervision is normally required. It is a prescription or clinician-administered medicine where it is approved.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
The identity record classes it as siRNA (Small Interfering RNA).
No source is stored against this line.
What is in the pack
2 mL, for subcutaneous use under the supervision of a clinician experienced in bleeding disorders. Antithrombin activity is measured before initiation and monitored on an FDA-cleared test thereafter.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Boxed warning for thrombotic events and for acute and recurrent gallbladder disease. Additional warning for hepatotoxicity, with liver tests required at baseline, monthly for at least six months after initiation and after dose increases, and periodically thereafter. Common adverse reactions above 10% are viral infection, nasopharyngitis and bacterial infection.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
GalNAc-conjugated siRNA, subcutaneous prefilled pen or vial
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
L, for subcutaneous use under the supervision of a clinician experienced in bleeding disorders. Antithrombin activity is measured before initiation and monitored on an FDA-cleared test thereafter.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
What is recorded as being sold
4 products list this as an active ingredient in the United States drug directory. 4 of them contain it and nothing else.
FDA National Drug Code directory · 58468-0347 · read 2026-08-29
They are sold as injection, solution and solution, taken subcutaneous.
FDA National Drug Code directory · 58468-0347 · read 2026-08-29
The regulator's established pharmacologic class for it is antithrombin-directed rna interaction [epc], decreased rna integrity [pe] and increased rna degradation [pe].
FDA National Drug Code directory · 58468-0347 · read 2026-08-29
1 published label names it as an active ingredient. 1 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-29
Qfitlia is subcutaneous at 3 DOSAGE FORMS AND STRENGTHS QFITLIA is a clear, colorless to pale yellow solution in a single-dose: Injection: 50 mg/0.5 mL prefilled pen Injection: 20 mg/0.2 mL vial Injection: 50 mg/0.5 mL (100 mg/mL) in a single-dos…, recorded as fda label in effect 2025-09-16 in the United States.
US prescribing information · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · read 2026-08-30
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Fitusiran studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That fitusiran is better than factor prophylaxis or emicizumab — neither was a randomised comparator
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That the trial bleeding rates transfer to the approved regimen, which is a different dose on a different schedule
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That an open-label, patient-reported bleeding count is free of expectation effects in either direction
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
How much did people take in the studies?
The sources RNAWiki checked hold nothing for this field.
Why it matters. A result belongs to an amount. Without the amount the result floats free.
What would answer it
A stored source that records it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Fitusiran are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
ATLAS-INH: 90.8% lower annualised bleeding rate in patients with inhibitors
In plain words
In people whose immune systems destroy replacement factor, monthly fitusiran cut the bleeding rate roughly tenfold, and two-thirds had no treated bleeds at all.
What was measured
Mean annualised bleeding rate over the 9-month efficacy period
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Open-label, randomised 2:1, 57 participants aged 12 and over with haemophilia A or B with inhibitors, previously on on-demand bypassing agents. Negative binomial model-based mean annualised bleeding rate 1.7 (95% CI 1.0 to 2.7) with fitusiran prophylaxis versus 18.1 (95% CI 10.6 to 30.8) with on-demand bypassing agents, a 90.8% reduction (95% CI 80.8 to 95.6; P<0.0001). 25 of 38 (66%) had zero treated bleeds versus 1 of 19 (5%).
Written into the record, not signed off as a reviewed claim
ATLAS-A/B: bleeding rate ratio of 0.101 without inhibitors
In plain words
In haemophilia without inhibitors, the bleeding rate on fitusiran was about a tenth of the on-demand rate, and half the treated group had no bleeds at all.
What was measured
Annualised bleeding rate, intention-to-treat
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Open-label, randomised 2:1, 120 participants across 45 sites in 17 countries. Estimated mean annualised bleeding rate 3.1 (95% CI 2.3 to 4.3) with fitusiran versus 31.0 (95% CI 21.1 to 45.5) with on-demand clotting factor concentrates; rate ratio 0.101 (95% CI 0.064 to 0.159; P<0.0001). 40 of 79 treated participants (51%) had no treated bleeds versus 2 of 40 (5%). No treatment-related thrombosis or deaths were reported in this trial.
Written into the record, not signed off as a reviewed claim
The original 80 mg monthly dose caused fatal thrombosis and is no longer approved
In plain words
The dose used in both pivotal trials is not the dose on the label. It caused clots, including a fatal one in the brain, and the FDA label now says it must not be used.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The QFITLIA boxed warning states that thrombotic events were reported in 2.6% of patients receiving the 80 mg once-monthly dose, at 2.3 events per 100 person-years, including a fatal event of cerebral venous sinus thrombosis, and that "the 80 mg once monthly dose is not approved or recommended for use". Thrombotic events were reported in 1.4% of patients on the approved prophylaxis regimen. Named risk factors are persistent antithrombin activity below 15%, an indwelling venous catheter and the post-operative setting when bleed-management guidelines were not followed.
Source
QFITLIA US prescribing information, boxed warning and section 5.1
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
Dosing was rebuilt around a lab value after the programme was paused
In plain words
After clots appeared, dosing stopped being a fixed monthly amount and became a target: keep antithrombin activity between 15% and 35%, and adjust the dose until it is.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The original dose regimen of 80 mg monthly was replaced by an antithrombin-based dose regimen targeting antithrombin activity of 15% to 35%, starting at 50 mg once every two months and adjusted individually. ATLAS-OLE evaluated this regimen; at interim data cut-off 213 participants were on it, 78% on a two-monthly schedule, with integrated safety analysed across 286 participants. The approved label requires antithrombin measurement before initiation, forbids starting if antithrombin activity is below 60%, and requires monitoring with an FDA-cleared test.
Written into the record, not signed off as a reviewed claim
Both pivotal trials compared fitusiran against on-demand treatment, not prophylaxis
In plain words
The tenfold bleeding reduction is against treating bleeds as they happen. It is not a comparison against the preventive treatments most patients would otherwise be on.
What was measured
That fitusiran prophylaxis is superior to established factor or emicizumab prophylaxis
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
ATLAS-INH randomised against on-demand bypassing agents and ATLAS-A/B against on-demand clotting factor concentrates. Neither randomised against factor prophylaxis or against emicizumab. Both were open-label, and the annualised bleeding rate depends on participant reporting of bleeds, which is not blinded in either direction.
Written into the record, not signed off as a reviewed claim
Liver enzyme elevation was the most common adverse event in both trials
In plain words
About a third of patients with inhibitors and about a quarter without had raised liver enzymes on treatment, and the label requires monthly liver testing for the first six months.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Increased alanine aminotransferase was the most frequent treatment-emergent adverse event in ATLAS-INH, in 13 of 41 safety-population participants (32%), with none in the comparator arm, and in 18 of 79 (23%) in ATLAS-A/B. The label requires liver tests at baseline, monthly for at least six months after initiation and after any dose increase, and periodically thereafter. Acute and recurrent gallbladder disease shares the boxed warning with thrombosis.
This order is fixed in code and does not count clicks or time on the page.
What is not here
7 questions this page could not answer
These sections were prepared and left out because there was nothing to put in them. They are listed rather than hidden, so the gaps in this record are visible.
What was measured, goal by goal — found nothing in the sources checked.
How close this is to real life — found nothing in the sources checked.
Felt, measured, or meaningful — found nothing in the sources checked.
How long anything takes — found nothing in the sources checked.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
The record as stored
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
Silences antithrombin to release the brake on clotting rather than replacing the missing factor, cutting the annualised bleeding rate by 90.8% against on-demand treatment in patients with inhibitors — and carrying a boxed warning for thrombosis written from its own trial data.
Recorded evidence blocks (3)
Q1
On the Fitusiran label: indicated for what?
"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…": indications and usage on Fitusiran's label. DailyMed label · 6dd2f8ac-6f90-4cbf-b197-97d74964135c · 2025-09-16
Q2
9 registered trials of Fitusiran — at which phases?
ClinicalTrials.gov — US Government work · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 4 source rows
✓ no critical contamination: no quarantine open
✓ canonical metadata passed: slug and display name present
✓ no raw internal fields: enforced by the copy-contract test over the rendered page
This is a record of evidence. It is not medical advice, and it does not say this substance suits you. Nothing here says any substance on RNAWiki is appropriate for a child.