This page shows what was measured, who it was measured in, and what that does not settle.
What Emicizumab does in the body
A subcutaneous injection, given as rarely as monthly, that stops the joint and muscle bleeds of haemophilia A without replacing the missing clotting factor
Clotting depends on two proteins meeting each other at the right moment. Factor VIII is the clamp that holds them together, and in haemophilia A the clamp is missing. Emicizumab is an antibody built with two different arms: one grabs the first protein, the other grabs the second, and by holding both it does the clamp’s job. It is not factor VIII and looks nothing like it, so the antibodies that destroy factor VIII in some patients simply do not recognise it.
What happened in people
Annualised bleeding rate of 2.9 against 23.3 events with no prophylaxis in haemophilia A with inhibitors, an 87% reduction (p<0.001)
✎ 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 recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
The limit that matters most
That an 87% reduction in bleeding over a year translates into preserved joint function over decades — the outcome that actually defines life with haemophilia and one that no trial has yet run long enough to measure
Where it acts
The surface of activated platelets at a site of injury, where the two clotting factors must be brought together
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 protein.
FDA substance registry · 7NL2E3F6K3 · 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.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 132 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.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
Randomisation
Randomisation means chance decides who gets which treatment.
A picture of it, and where the picture fails
It is like a coin toss deciding the groups.
Where that stops being true. A coin toss is fair once. Fairness here comes from doing it for everyone.
What people get wrong. It is thought to make groups identical. It makes them similar on average, including on things nobody measured.
Allocation of participants to arms by a chance process, so that unmeasured factors are balanced in expectation.
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.
Difference in treated bleeding rate between emicizumab prophylaxis and no prophylaxis
✓ The study showed what it set out to show
Who was studied
HAVEN 1 (NCT02622321) — emicizumab prophylaxis in haemophilia A with inhibitors
How many people
109
Study design
Phase 3 multicentre randomised open-label trial with an intra-individual comparison cohort
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Annualised bleeding rate 2.9 (95% CI 1.7 to 5.0) versus 23.3 (95% CI 12.3 to 43.9), an 87% reduction, p < 0.001
Repeated elsewhere
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. Thrombotic microangiopathy and thrombosis in 2 participants each, all of whom had received multiple infusions of activated prothrombin complex concentrate for breakthrough bleeding. The control arm was no prophylaxis, which was the standard of care in this population but is a low bar.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Subcutaneous injection, weekly, fortnightly or every four weeks
Interval reported. 95% CI 1
Written into the record, not signed off as a reviewed claim.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
HAVEN 3 — emicizumab prophylaxis in haemophilia A without inhibitors (NCT02847637) · a recorded source, not a stored snapshot
Difference in treated bleeding rate between each emicizumab schedule and no prophylaxis
✓ The study showed what it set out to show
Who was studied
HAVEN 3 (NCT02847637) — emicizumab prophylaxis in haemophilia A without inhibitors
How many people
152
Study design
Phase 3 multicentre randomised trial, 2:2:1, with an intra-individual comparison cohort
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
1.5 events (95% CI 0.9 to 2.5) weekly and 1.3 events (95% CI 0.8 to 2.3) fortnightly versus 38.2 events (95% CI 22.9 to 63.8), reductions of 96% and 97%, p < 0.001 for both
Repeated elsewhere
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. No thrombotic or thrombotic microangiopathy events, no antidrug antibodies and no new factor VIII inhibitors in this trial. The comparison against no prophylaxis in a population for whom factor VIII prophylaxis already existed is a weaker control than the intra-individual analysis.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Subcutaneous injection, weekly, fortnightly or every four weeks
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
HAVEN 3 — emicizumab prophylaxis in haemophilia A without inhibitors (NCT02847637) · a recorded source, not a stored snapshot
Annualised bleeding rate on emicizumab against the same patient’s previous factor VIII prophylaxis
✓ The study showed what it set out to show
Who was studied
HAVEN 3 intra-individual comparison against prior factor VIII prophylaxis
How many people
48
Study design
Within-patient comparison in participants from a prior non-interventional study
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
68% lower annualised bleeding rate on emicizumab, p < 0.001
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. Not randomised. Each patient is their own control, which removes between-patient variation but not the effect of time, of changing adherence, or of the difference between a non-interventional observation period and a trial.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Subcutaneous injection, weekly, fortnightly or every four weeks
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
HAVEN 3 — emicizumab prophylaxis in haemophilia A without inhibitors (NCT02847637) · a recorded source, not a stored snapshot
Incidence of thrombotic microangiopathy and thrombotic events with concomitant activated prothrombin complex concentrate
✗ The study did not show it
Who was studied
Pooled clinical trial safety experience for thrombotic microangiopathy with concomitant activated prothrombin complex concentrate
How many people
391
Study design
Pooled safety analysis across the emicizumab clinical programme
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Thrombotic microangiopathy in 3 of 391 patients (0.8%) overall and 3 of 37 (8.1%) of those receiving at least one dose of activated prothrombin complex concentrate
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. The denominator that matters is 37, not 391. Presentations were thrombocytopenia, microangiopathic haemolytic anaemia and acute kidney injury without severe ADAMTS13 deficiency, improving within a week of stopping the concentrate.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Subcutaneous injection, weekly, fortnightly or every four weeks
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
HAVEN 3 — emicizumab prophylaxis in haemophilia A without inhibitors (NCT02847637) · a recorded source, not a stored snapshot
What we know
RNAWiki holds 4 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
Emicizumab
What a person takes: Subcutaneous injection, weekly, fortnightly or every four weeks.
The measurement behind this step
A ready-to-use solution in single-dose vials at several strengths, injected under the skin of the abdomen, upper arm or thigh, and self-administered or given by a carer. The schedule is chosen by the patient and clinician; all three maintenance regimens were evaluated in the trial programme. No intravenous access is needed, which for infants and small children is the practical difference between the treatment being feasible and not.
Getting in
An injection under the skin, as rarely as once a month
Given subcutaneously, weekly, fortnightly or monthly depending on the schedule chosen. For a family used to finding a vein in a small child several times a week, that is the headline change.
╌╌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
Supplied as single-dose vials at 12 mg/0.4 mL, 30 mg/mL, 60 mg/0.4 mL, 105 mg/0.7 mL, 150 mg/mL and 300 mg/2 mL. Subcutaneous administration is possible because the molecule is a stable IgG4 with antibody pharmacokinetics, unlike factor VIII, which has a half-life measured in hours and must be given intravenously.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
Reaching the cell
It circulates for weeks and works in the plasma
The antibody stays in the bloodstream for a long time, which is why dosing can be so infrequent. It never enters a cell; the whole reaction it enables happens on surfaces in the blood.
╌╌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 145.6 kDa IgG4 with neonatal Fc receptor recycling gives a half-life of several weeks. The consequence appears twice on this page: it permits monthly dosing, and it means the interaction with activated prothrombin complex concentrate persists for weeks after the last injection.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
What it acts on
One arm grabs factor IXa, the other grabs factor X
Ordinary antibodies have two identical arms. This one was built with two different arms, each recognising a different clotting protein, so a single molecule can hold both at once.
╌╌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 humanised modified IgG4 bispecific antibody binding factor IXa and factor X. The label notes it has no structural relationship or sequence homology to factor VIII and therefore does not induce or enhance the development of direct inhibitors to factor VIII — which is the entire reason it works in the inhibitor population.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
The change it makes
Held together, the two proteins can finally react
Factor IXa can cut factor X, but only if something holds them in position. That is all factor VIII ever did. The antibody does the same job by geometry rather than by chemistry.
╌╌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 label describes it as bridging activated factor IX and factor X to restore the function of missing activated factor VIII. Affinity for both arms is deliberately modest: an antibody that bound either factor tightly would sequester it, and the molecule had to be engineered away from maximum affinity to work as a catalyst rather than an inhibitor.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
What that does for a person
Factor Xa appears, thrombin follows, and bleeds stop happening
The cascade runs at something approaching normal speed. Spontaneous bleeds into joints and muscles largely stop: nearly two in three patients with inhibitors had none at all over the trial.
╌╌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
Annualised bleeding rate 2.9 against 23.3 in the inhibitor population, an 87% reduction, with 63% having zero bleeds against 6%. In the non-inhibitor population 1.5 and 1.3 against 38.2, reductions of 96% and 97%, with 56% and 60% having no treated bleeds against 0%.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
What that does for a person
And the clotting tests stop telling the truth
Because the drug restores the very reaction the standard clotting test measures, that test now reads normal no matter what. Every assay built on it, including the one that detects inhibitors, becomes unusable.
╌╌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 label directs that intrinsic pathway clotting-based laboratory tests should not be used, listing activated clotting time, aPTT, one-stage aPTT-based single-factor assays, aPTT-based activated protein C resistance and clotting-based Bethesda assays. Monitoring requires a chromogenic factor VIII assay using bovine reagents, which the antibody does not bind.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 6 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.
Adults and children from birth with haemophilia A, with or without inhibitors, as continuous prophylaxis. It does not treat a bleed that is already happening — that still needs factor concentrate or a bypassing agent.
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: “All clinical trials included pediatric patients in the following age group: 47 adolescents (12 years up to less than 18 years).”
US prescribing information · 2483adba-fab6-4d1b-96c5-c195577ed071 · read 2026-08-30
On older people, the label states: “Clinical studies of HEMLIBRA did not include a sufficient number of patients aged 65 and over to determine whether they respond differently from younger patients.”
US prescribing information · 2483adba-fab6-4d1b-96c5-c195577ed071 · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary There are no available data on HEMLIBRA use in pregnant women to inform a drug-associated risk of major birth defects and miscarriage.”
US prescribing information · 2483adba-fab6-4d1b-96c5-c195577ed071 · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary There is no information regarding the presence of emicizumab-kxwh in human milk, the effects on the breastfed child, or the effects on milk production.”
US prescribing information · 2483adba-fab6-4d1b-96c5-c195577ed071 · read 2026-08-30
Where the result stopped carrying
Thrombotic microangiopathy and thrombosis appeared in the pivotal trial in patients given activated prothrombin complex concentrate for breakthrough bleeding, producing the boxed warning
The drug abolishes the usability of every aPTT-based coagulation test, including the assay used to detect factor VIII inhibitors, so patients on it cannot be monitored by conventional means
Anti-emicizumab antibodies including neutralising antibodies have developed in treated patients despite none being detected in the pivotal trials
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
Subcutaneous injection, weekly, fortnightly or every four weeks
✎ 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 Monoclonal Antibody (mAb).
No source is stored against this line.
What is in the pack
A ready-to-use solution in single-dose vials at several strengths, injected under the skin of the abdomen, upper arm or thigh, and self-administered or given by a carer. The schedule is chosen by the patient and clinician; all three maintenance regimens were evaluated in the trial programme. No intravenous access is needed, which for infants and small children is the practical difference between the treatment being feasible and not.
✎ 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
Carries a boxed warning for thrombotic microangiopathy and thromboembolism when a cumulative average of more than 100 U/kg per 24 hours of activated prothrombin complex concentrate is given for 24 hours or more to a patient on emicizumab; the label directs that the concentrate be stopped and emicizumab suspended if symptoms occur. Thrombotic microangiopathy occurred in 8.1% of trial patients who received at least one dose of the concentrate. Anti-emicizumab antibodies including neutralising antibodies have developed in treated patients, and loss of efficacy should prompt investigation. The drug interferes with the activated clotting time, the aPTT and every assay derived from it, including clotting-based Bethesda assays for factor VIII inhibitor titre; those tests must not be used. The commonest adverse event in trials was a low-grade injection-site reaction.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
HAVEN 1 — emicizumab prophylaxis in haemophilia A with inhibitors (NCT02622321) · a recorded source, not a stored snapshot
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
Subcutaneous injection, weekly, fortnightly or every four weeks
✎ 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
The schedule is chosen by the patient and clinician; all three maintenance regimens were evaluated in the trial programme. No intravenous access is needed, which for infants and small children is the practical difference between the treatment being feasible and not.
✎ 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
15 products list this as an active ingredient in the United States drug directory. 15 of them contain it and nothing else.
FDA National Drug Code directory · 71124-0012 · read 2026-08-29
They are sold as injection, solution, liquid and solution, taken subcutaneous.
FDA National Drug Code directory · 71124-0012 · 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 · 2483adba-fab6-4d1b-96c5-c195577ed071 · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 2483adba-fab6-4d1b-96c5-c195577ed071 · read 2026-08-29
Hemlibra is subcutaneous at 3 DOSAGE FORMS AND STRENGTHS HEMLIBRA is available as a colorless to slightly yellow solution in single-dose vials., recorded as fda label in effect 2025-07-11 in the United States.
US prescribing information · 2483adba-fab6-4d1b-96c5-c195577ed071 · 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 Emicizumab 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 an 87% reduction in bleeding over a year translates into preserved joint function over decades — the outcome that actually defines life with haemophilia and one that no trial has yet run long enough to measure
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 intra-individual comparison against prior factor VIII prophylaxis is equivalent to a randomised head-to-head; it is a within-patient before-and-after in 48 people
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 absence of detected antidrug antibodies in the pivotal trials establishes long-term immunogenicity safety; the label warns that neutralising antibodies have since developed in treated patients
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 Emicizumab 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.
Bleeding fell by 87%, and two in three patients had no bleeds at all
In plain words
In patients with haemophilia A and inhibitors, the annual bleeding rate was 2.9 events on emicizumab against 23.3 on no prophylaxis. Twenty-two of 35 treated patients had zero bleeds; one of 18 untreated did.
What was measured
Annualised rate of treated bleeding events
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
HAVEN 1 enrolled 109 male participants aged 12 or older with haemophilia A and factor VIII inhibitors. Those previously on episodic bypassing-agent treatment were randomised 2:1 to once-weekly subcutaneous emicizumab (group A, 35) or no prophylaxis (group B, 18). The annualised bleeding rate was 2.9 events (95% CI 1.7 to 5.0) against 23.3 events (95% CI 12.3 to 43.9), a difference of 87% in favour of emicizumab (p<0.001). Zero bleeding events occurred in 22 of 35 (63%) against 1 of 18 (6%). Among 24 participants in group C who had previously received bypassing-agent prophylaxis and had taken part in a non-interventional study, emicizumab reduced the bleeding rate by 79% against their own prior prophylaxis (p<0.001). The most frequent adverse events were injection-site reactions in 15%. No antidrug antibodies were detected in the primary analysis.
Written into the record, not signed off as a reviewed claim
It beat patients’ own previous factor VIII prophylaxis by 68%
In plain words
In people without inhibitors, bleeding fell 96 to 97% against no prophylaxis. More striking, in 48 people who switched from their own factor VIII regimen, bleeding fell by a further 68%.
What was measured
Annualised rate of treated bleeding events, including an intra-individual comparison against prior factor VIII prophylaxis
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
HAVEN 3 randomised 152 participants aged 12 or older, previously on episodic factor VIII, in a 2:2:1 ratio to emicizumab 1.5 mg/kg weekly (group A), 3.0 mg/kg every two weeks (group B), or no prophylaxis (group C). Annualised bleeding rates were 1.5 events (95% CI 0.9 to 2.5) and 1.3 events (95% CI 0.8 to 2.3) against 38.2 events (95% CI 22.9 to 63.8), reductions of 96% and 97% (p<0.001 for both). No treated bleeding occurred in 56% and 60% of the two prophylaxis groups, against 0% of the control group. The intra-individual comparison in 48 participants who had been on factor VIII prophylaxis in a prior non-interventional study found an annualised bleeding rate 68% lower on emicizumab (p<0.001). There were no thrombotic or thrombotic microangiopathy events, no antidrug antibodies and no new factor VIII inhibitors in this trial.
Written into the record, not signed off as a reviewed claim
Combined with the drug it replaced, it destroys small blood vessels
In plain words
Patients who had a breakthrough bleed and were given activated prothrombin complex concentrate on top of emicizumab developed thrombotic microangiopathy — clots in the smallest vessels, destroying red cells and damaging the kidneys. Three of 37 such patients, against three in the whole 391-patient programme.
What was measured
Incidence of thrombotic microangiopathy in patients receiving activated prothrombin complex concentrate while on emicizumab prophylaxis
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The HEMLIBRA boxed warning states that thrombotic microangiopathy and thrombotic events were reported when on average a cumulative amount of more than 100 U/kg per 24 hours of activated prothrombin complex concentrate was given for 24 hours or more to patients on emicizumab prophylaxis. In clinical trials thrombotic microangiopathy occurred in 0.8% of patients overall (3 of 391) and in 8.1% (3 of 37) of those who received at least one dose of activated prothrombin complex concentrate. Patients presented with thrombocytopenia, microangiopathic haemolytic anaemia and acute kidney injury without severe ADAMTS13 deficiency, and improved within a week of stopping the concentrate; one resumed emicizumab after resolution. The mechanism is additive: the antibody is already substituting for factor VIII, and the concentrate supplies activated factors on top of it. The drug’s long half-life means the interaction persists for weeks after the last dose.
Source
HEMLIBRA (emicizumab-kxwh) prescribing information, boxed warning and section 5.1 Thrombotic Microangiopathy Associated with HEMLIBRA and aPCC
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
It makes the standard clotting tests read wrong, permanently
In plain words
Emicizumab interferes with the activated partial thromboplastin time and every test built on it — including the test used to detect factor VIII inhibitors and to measure factor VIII activity. Those tests cannot be used at all in a patient taking it.
What was measured
Interference with activated clotting time, activated partial thromboplastin time and all aPTT-derived assays
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The label states that the drug interferes with the activated clotting time, the activated partial thromboplastin time, and coagulation tests based on aPTT including one-stage single-factor assays, aPTT-based activated protein C resistance and clotting-based Bethesda assays for factor VIII inhibitor titre, and directs that intrinsic pathway clotting-based laboratory tests should not be used. This is a direct consequence of the mechanism: the antibody restores the clotting reaction the aPTT measures, so it normalises or shortens the aPTT regardless of how much factor VIII is present. Monitoring is possible only with a chromogenic assay using bovine reagents, which the antibody does not recognise. The audit point here is unusual: the drug did not have a surrogate endpoint problem because it removed the possibility of using surrogates at all, and the trials were therefore forced to count bleeds.
Source
HEMLIBRA (emicizumab-kxwh) prescribing information, section 5.4 Laboratory Coagulation Test Interference and section 7.2
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
Fewer bleeds is not the same as fewer damaged joints
In plain words
The trials counted bleeding episodes over about a year. The reason bleeds matter in haemophilia is the joint destruction that accumulates over decades, and that takes decades to measure.
What was measured
That an 87% reduction in bleeding episodes over a year translates into preserved joints over a lifetime — highly plausible, mechanistically expected, and not yet measured
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
HAVEN 1 and HAVEN 3 measured annualised bleeding rate as the primary endpoint over trial periods of roughly six months to a year. Annualised bleeding rate is a real clinical outcome and a far better one than a clotting time, which is why this page grades the drug more favourably than most in this file. It is nonetheless an intermediate: the endpoint that governs a person’s life with haemophilia A is arthropathy, and joint health in patients started on emicizumab from infancy will not be known for twenty years. The intra-individual comparison against prior factor VIII prophylaxis is the strongest evidence available that the difference is likely to matter, and it is a within-patient comparison in 48 people, not a randomised one.
Written into the record, not signed off as a reviewed claim
It prevents bleeds and cannot treat one
In plain words
Emicizumab is prophylaxis only. When a bleed happens anyway, it still needs factor concentrate or a bypassing agent — which is precisely the situation the boxed warning is about.
What was measured
That prophylaxis alone is sufficient management — it is not, and the necessary supplementary treatment is the one that carries the boxed warning
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The indication is confined to routine prophylaxis to prevent or reduce the frequency of bleeding episodes. The antibody provides a low, constant level of factor-VIII-like activity, which is enough to prevent spontaneous bleeding but not to secure haemostasis in trauma or surgery. So the population most exposed to the boxed warning is defined by the drug’s own limitation: a patient with inhibitors, on emicizumab, who has a breakthrough bleed and therefore needs a bypassing agent. The label directs that if activated prothrombin complex concentrate must be used, it be discontinued and emicizumab suspended if symptoms of thrombotic microangiopathy appear, and notes that the antibody’s long half-life means the interaction persists well beyond the last dose.
Source
HEMLIBRA (emicizumab-kxwh) prescribing information, section 1 Indications and Usage 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
Where else this substance is registered
FDA substance identifier (UNII)
7NL2E3F6K3
RxNorm concept
1989799
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Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
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Safety mode resolved
The identity record classes it as Monoclonal Antibody (mAb).
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Canonical metadata present
slug and display name present
What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
What the approval register records
1 approved application covers products containing this substance. The earliest was BLA761083, approved 20171116 to GENENTECH INC.
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What is not here
7 questions this page could not answer
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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.
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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.
A bispecific antibody with one arm on factor IXa and one on factor X, holding them together in place of the missing factor VIII, which cut treated bleeding by 87% against no prophylaxis in patients with inhibitors and by 68% against a patient’s own previous factor VIII prophylaxis — measured as bleeds rather than laboratory numbers, because the drug makes the laboratory numbers meaningless, and carrying a boxed warning for the clotting catastrophe that follows when it is combined with the bypassing agent it replaced.
Recorded evidence blocks (8)
Q1
On the Emicizumab label: indicated for what?
"HEMLIBRA is indicated for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients ages newborn and older with hemophilia A (congenital factor VIII deficiency) with or without factor VIII inhibitors. HEMLIBRA is a bispecific factor IXa- and factor X-directed antibody…": indications and usage on Emicizumab's label. DailyMed label · 2483adba-fab6-4d1b-96c5-c195577ed071 · 2025-07-11
Q2
34 registered trials of Emicizumab — at which phases?
"The Sponsor decided to terminate the study early for several reasons (low enrollment, limited variety of surgery types, and available scientific data)."; 6 of 34 registered studies
Show the evidence
Trial
NCT03361137
terminated; "The Sponsor decided to terminate the study early for several reasons (low enrollment, limited variety of surgery types, and available scientific data)."
NCT03921294
terminated; "Global COVID-19 pandemic prevented further study visits or enrollment."
NCT04030052
withdrawn; "The Emi PUPs and Nuwiq ITI study has been closed due to slow enrollment and study site startup."
NCT04303559
terminated; "The INHIBIT Trials IDSMB, in a letter dated 05-18-22, recommended, given the slow enrollment, that the INHIBIT Trials be discontinued due to futility."
NCT04303572
terminated; "The INHIBIT Trials IDSMB, in a letter dated 05-18-22, recommended, given the slow enrollment, that the INHIBIT Trials be discontinued due to futility."
NCT04690322
withdrawn; "Due to COVID-19 pandemic, recruitment was temporarily put on hold. We are withdrawing this registration due to a recent amendment to the protocol that includes major changes to data elements. A new registration will be submitted for the…"
recorded 2026-09-01 · last checked 2026-09-04
Q4
Emicizumab's half-life is 1.6 ± 1 day — which schedules were studied?
1.6 ± 1 day, the half-life Emicizumab's label states: "C max, ss (µg/mL) 55.1 ± 15.9 58.3 ± 16.4 67 ± 17.7 AUC ss,τ (µg/mL*day) 376 ± 109 752 ± 218 1503 ± 437 C trough, ss (µg/mL) 51.2± 15.2 46.9 ± 14.8 38.5 ± 14.2 C max / C trough ratio (µg/mL) 1.08 ± 0.03 1.26 ± 0.12 1.85 ± 0.47 Absorption Following subcutaneous administration, the mean (± SD) absorption half-life was…" DailyMed label · 2483adba-fab6-4d1b-96c5-c195577ed071 · 2025-07-11
bioavailability 80.4 %.
Show the evidence
half lifepharmacokinetics
1.6 ± 1 day; C max, ss (µg/mL) 55.1 ± 15.9 58.3 ± 16.4 67 ± 17.7 AUC ss,τ (µg/mL*day) 376 ± 109 752 ± 218 1503 ± 437 C trough, ss (µg/mL) 51.2± 15.2 46.9 ± 14.8 38.5 ± 14.2 C max / C trough ratio (µg/mL) 1.08 ± 0.03 1.26 ± 0.12 1.85 ± 0.47 Absorption Following subcutaneous administration, the mean (± SD) absorption half-life was 1.6 ± 1 day.
bioavailabilitypharmacokinetics
80.4 %; The absolute bioavailability following subcutaneous administration of 1 mg/kg was between 80.4% and 93.1%.
recorded 2025-07-11 · last checked 2026-09-04
Q5
Which one trial of Emicizumab posted no result?
Posted no result
1 of 1 completed trials
Registrations
NCT04188639
Completion dates
oldest 2023-01-04
Show the evidence
TrialNCT04188639
2023-01-04
Q6
At the median, Emicizumab's trials enrolled 51 people — anything larger?
Median enrolment
51
Largest enrolment
360
Registered trials counted
33
Q7
What do 816 spontaneous reports say about Emicizumab — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Emicizumab appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 816 reaction mentions were counted: haemorrhage 267; haemarthrosis 199; fall 82; muscle haemorrhage 63. FAERS via Open Targets · CHEMBL3833393 · 2026-06-24
Show the evidence
haemorrhage
267
haemarthrosis
199
fall
82
muscle haemorrhage
63
activated partial thromboplastin time prolonged
52
injury
36
4 more recorded rows
contusion
32
gastrointestinal haemorrhage
30
haematoma
29
epistaxis
26
recorded 2026-06-24 · last checked 2026-09-04
Q8
Which 10 reactions does Emicizumab's label not list?
ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
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✓ source coverage passed: 5 source rows
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