Emicizumab side effects: what 12,196 FDA adverse event reports show
Drug class
Bispecific factor ixa- and factor x-directed antibody
Brand names
Hemlibra
Who reports
12,196 reports · 38% serious · 393 with death outcome · 4% female
Used for
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. H.
What it is
Emicizumab-kxwh is a humanized monoclonal modified immunoglobulin G4 (IgG4) bispecific antibody binding factor IXa and factor X. Emicizumab-kxwh has an approximate molecular weight of 145.6 kDa and is produced in genetically engineered mammalian (Chinese hamster ovary) cells.
Boxed warning
THROMBOTIC MICROANGIOPATHY AND THROMBOEMBOLISM Cases of thrombotic microangiopathy and thrombotic events were reported when on average a cumulative amount of >100 U/kg/24 hours of activated prothrombin complex concentrate was administered for 24 hours or more to patients receiving HEMLIBRA prophylaxis.
Causality screen of the 40 strongest signals
What the badges mean
- Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
- Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
- Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
- Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
- Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
Strongest disproportionality signals
Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 735 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Anti factor viii antibody increased | 24 | 408.1 261.4–637.3ROR 408.9 · χ² 7,521 / p <1e-300 | 260.6 EB05 184.3 · IC025 +4.7 3/3 methods agree | Likely indication confounding term in indications | serious n=20 | no trial data cached |
| Joint microhaemorrhage | 11 | 324.9 170.4–619.4ROR 325.2 · χ² 2,712 / p <1e-300 | 185.4 EB05 110.5 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=8 | no trial data cached |
| Testicular haemorrhage | 11 | 243.7 129.5–458.4ROR 243.9 · χ² 2,115 / p <1e-300 | 156.0 EB05 92.9 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=6 | no trial data cached |
| Haemophilic arthropathy | 23 | 188.9 122.8–290.5ROR 189.2 · χ² 3,698 / p <1e-300 | 149.1 EB05 104.7 · IC025 +4.5 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=18 | no trial data cached |
| Haemarthrosis | 844 | 178.5 166.7–191.2ROR 191.6 · χ² 134,605 / p <1e-300 | 160.9 EB05 152.0 · IC025 +7.1 3/3 methods agree | Not in label — unassessed | serious PRR 205.9 | no trial data cached |
| Spontaneous haemorrhage | 87 | 161.7 129.8–201.3ROR 162.8 · χ² 12,529 / p <1e-300 | 143.0 EB05 119.5 · IC025 +6.0 3/3 methods agree | Not in label — unassessed | serious n=43 | no trial data cached |
| Muscle haemorrhage | 306 | 141.2 125.8–158.4ROR 144.8 · χ² 39,174 / p <1e-300 | 129.3 EB05 117.6 · IC025 +6.6 3/3 methods agree | Not in label — unassessed | serious n=215 | no trial data cached |
| Traumatic haemorrhage | 122 | 121.7 101.3–146.1ROR 122.9 · χ² 13,506 / p <1e-300 | 111.6 EB05 95.9 · IC025 +6.0 3/3 methods agree | Not in label — unassessed | serious n=65 | no trial data cached |
| Tooth socket haemorrhage | 15 | 113.8 67.5–191.8ROR 113.9 · χ² 1,466 / p <1e-300 | 94.2 EB05 60.6 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=5 | no trial data cached |
| Anti factor viii antibody positive | 34 | 109.2 77.3–154.5ROR 109.5 · χ² 3,323 / p <1e-300 | 97.2 EB05 72.7 · IC025 +4.8 3/3 methods agree | Lab value / disease marker | serious n=25 | no trial data cached |
| Soft tissue haemorrhage | 19 | 90.1 56.8–142.9ROR 90.2 · χ² 1,506 / p <1e-300 | 79.0 EB05 53.5 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious n=12 | no trial data cached |
| Tongue haemorrhage | 58 | 88.4 68.0–115.1ROR 88.9 · χ² 4,682 / p <1e-300 | 81.9 EB05 65.7 · IC025 +5.2 3/3 methods agree | Not in label — unassessed | serious n=23 · 79% consumer | no trial data cached |
| Haemorrhage | 4,539 | 77.5 75.6–79.4ROR 122.3 · χ² 329,136 / p <1e-300 | 74.1 EB05 72.3 · IC025 +6.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 38.5 · 82% consumer | no trial data cached |
| Mouth haemorrhage | 226 | 54.2 47.6–61.9ROR 55.2 · χ² 11,395 / p <1e-300 | 52.4 EB05 46.9 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=71 · 88% consumer | no trial data cached |
| Haematoma muscle | 36 | 53.8 38.6–75.0ROR 54.0 · χ² 1,758 / p <1e-300 | 50.9 EB05 38.4 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=35 | no trial data cached |
| Lip haemorrhage | 38 | 52.5 38.0–72.4ROR 52.6 · χ² 1,811 / p <1e-300 | 49.7 EB05 37.8 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=11 · 84% consumer | no trial data cached |
| Factor viii inhibition | 29 | 48.1 33.3–69.6ROR 48.3 · χ² 1,256 / p 2e-275 | 45.5 EB05 33.2 · IC025 +4.1 3/3 methods agree | Not in label — unassessed | serious n=21 · 93% clinician | no trial data cached |
| Lip injury | 31 | 41.4 29.0–59.1ROR 41.5 · χ² 1,153 / p 4e-253 | 39.5 EB05 29.2 · IC025 +4.0 3/3 methods agree | Labeled (related wording) related wording | serious n=11 · 81% consumer | no trial data cached |
| Ear injury | 10 | 35.4 18.9–66.1ROR 35.4 · χ² 294 / p 3e-66 | 32.7 EB05 18.9 · IC025 +2.7 3/3 methods agree | Labeled (related wording) related wording | serious n=3 | no trial data cached |
| Tongue injury | 19 | 35.3 22.4–55.5ROR 35.3 · χ² 587 / p 7e-130 | 33.5 EB05 22.7 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=6 | no trial data cached |
| Mouth injury | 28 | 31.9 22.0–46.4ROR 32.0 · χ² 793 / p 1e-174 | 30.8 EB05 22.3 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=10 · 79% consumer | no trial data cached |
| Traumatic haematoma | 19 | 30.6 19.4–48.1ROR 30.6 · χ² 505 / p 3e-112 | 29.3 EB05 19.8 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=17 | no trial data cached |
| Ear haemorrhage | 32 | 27.4 19.4–38.9ROR 27.5 · χ² 777 / p 3e-171 | 26.6 EB05 19.8 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=6 · 91% consumer | no trial data cached |
| Activated partial thromboplastin time prolonged | 78 | 26.6 21.3–33.2ROR 26.8 · χ² 1,867 / p <1e-300 | 26.1 EB05 21.6 · IC025 +4.1 3/3 methods agree | Lab value / disease marker | serious n=60 · 100% clinician | no trial data cached |
| Device related thrombosis | 15 | 26.5 15.9–44.1ROR 26.5 · χ² 338 / p 1e-75 | 25.3 EB05 16.2 · IC025 +3.0 3/3 methods agree | Reporting / coding artifact | serious n=15 | no trial data cached |
| Renal haemorrhage | 29 | 24.6 17.1–35.5ROR 24.7 · χ² 624 / p 4e-138 | 23.9 EB05 17.5 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=22 · 79% consumer | no trial data cached |
| Ligament sprain | 133 | 23.3 19.7–27.6ROR 23.6 · χ² 2,781 / p <1e-300 | 22.9 EB05 19.9 · IC025 +4.1 3/3 methods agree | Not in label — unassessed | serious n=36 · 83% consumer | no trial data cached |
| Haemoperitoneum | 10 | 22.0 11.8–41.1ROR 22.0 · χ² 178 / p 8e-41 | 20.6 EB05 11.2 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Skin laceration | 125 | 20.0 16.8–23.8ROR 20.2 · χ² 2,209 / p <1e-300 | 19.7 EB05 17.0 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious PRR 12.2 · 86% consumer | no trial data cached |
| Head injury | 361 | 19.7 17.8–21.9ROR 20.3 · χ² 6,336 / p <1e-300 | 19.5 EB05 17.9 · IC025 +4.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 10.8 · 79% consumer | no trial data cached |
| Joint injury | 241 | 19.4 17.1–22.1ROR 19.8 · χ² 4,155 / p <1e-300 | 19.2 EB05 17.3 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious PRR 13.1 · 84% consumer | no trial data cached |
| Intercepted product storage error | 34 | 17.2 12.2–24.1ROR 17.2 · χ² 497 / p 3e-110 | 16.8 EB05 12.5 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | – | no trial data cached |
| Drug specific antibody present | 64 | 17.0 13.3–21.7ROR 17.1 · χ² 939 / p 2e-206 | 16.7 EB05 13.5 · IC025 +3.5 3/3 methods agree | Lab value / disease marker | serious n=37 | no trial data cached |
| Face injury | 36 | 16.3 11.7–22.6ROR 16.4 · χ² 497 / p 2e-110 | 16.0 EB05 11.9 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=15 · 83% consumer | no trial data cached |
| Gingival bleeding | 125 | 15.7 13.2–18.8ROR 15.9 · χ² 1,696 / p <1e-300 | 15.6 EB05 13.4 · IC025 +3.6 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 11.4 · 78% consumer | no trial data cached |
| Limb injury | 237 | 15.1 13.3–17.1ROR 15.3 · χ² 3,073 / p <1e-300 | 14.9 EB05 13.4 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 9.3 · 84% consumer | no trial data cached |
| Procedural haemorrhage | 34 | 15.0 10.7–21.0ROR 15.0 · χ² 426 / p 7e-95 | 14.6 EB05 10.7 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=27 | no trial data cached |
| Eye injury | 25 | 14.3 9.6–21.2ROR 14.3 · χ² 293 / p 5e-66 | 13.7 EB05 9.4 · IC025 +2.8 3/3 methods agree | Labeled (related wording) related wording | serious n=10 · 88% consumer | no trial data cached |
| Extradural haematoma | 11 | 14.2 7.9–25.8ROR 14.2 · χ² 121 / p 2e-28 | 12.6 EB05 6.5 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial data cached |
| Intra-abdominal haemorrhage | 19 | 13.7 8.7–21.5ROR 13.7 · χ² 209 / p 1e-47 | 12.8 EB05 8.2 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=19 | no trial data cached |
Trial evidence (ClinicalTrials.gov)
Most frequently reported reactions
By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Haemorrhage | 4,539 | 77.5 75.6–79.4ROR 122.3 · χ² 329,136 / p <1e-300 | 74.1 EB05 72.3 · IC025 +6.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 38.5 · 82% consumer | no trial data cached |
| Haemarthrosis | 844 | 178.5 166.7–191.2ROR 191.6 · χ² 134,605 / p <1e-300 | 160.9 EB05 152.0 · IC025 +7.1 3/3 methods agree | Not in label — unassessed | serious PRR 205.9 | no trial data cached |
| Off label use (used outside approved label) | 790 | 1.6 1.5–1.7ROR 1.6 · χ² 162 / p 2e-37 | 1.6 EB05 1.5 · IC025 +0.5 | Reporting / coding artifact | serious PRR 1.3 | no trial data cached |
| No adverse event | 788 | 7.6 7.1–8.1ROR 8.1 · χ² 4,539 / p <1e-300 | 7.6 EB05 7.1 · IC025 +2.8 3/3 methods agree | Reporting / coding artifact | serious PRR 1.4 | no trial data cached |
| Fall | 667 | 3.4 3.2–3.7ROR 3.6 · χ² 1,162 / p 6e-255 | 3.4 EB05 3.2 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 2.7 · 71% consumer | no trial data cached |
| Arthralgia (joint pain) | 507 | 2.1 1.9–2.3ROR 2.1 · χ² 293 / p 7e-66 | 2.1 EB05 1.9 · IC025 +0.9 | Labeled adverse reaction exact term | serious PRR 1.8 · 73% consumer | no trial data cached |
| Epistaxis (nosebleed) | 411 | 9.4 8.6–10.3ROR 9.7 · χ² 3,073 / p <1e-300 | 9.3 EB05 8.6 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 5.1 · 85% consumer | no trial data cached |
| Contusion | 404 | 7.2 6.5–7.9ROR 7.4 · χ² 2,151 / p <1e-300 | 7.1 EB05 6.6 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 4.7 · 81% consumer | no trial data cached |
| Head injury | 361 | 19.7 17.8–21.9ROR 20.3 · χ² 6,336 / p <1e-300 | 19.5 EB05 17.9 · IC025 +4.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 10.8 · 79% consumer | no trial data cached |
| Pain | 332 | 0.9 0.8–1.0ROR 0.9 · χ² 2 / p 0.068 | 0.9 EB05 0.8 · IC025 -0.3 PRR-only: not supported by EBGM or IC | Labeled adverse reaction exact term | serious PRR 0.7 · 79% consumer | no trial data cached |
| Muscle haemorrhage | 306 | 141.2 125.8–158.4ROR 144.8 · χ² 39,174 / p <1e-300 | 129.3 EB05 117.6 · IC025 +6.6 3/3 methods agree | Not in label — unassessed | serious n=215 | no trial data cached |
| Joint injury | 241 | 19.4 17.1–22.1ROR 19.8 · χ² 4,155 / p <1e-300 | 19.2 EB05 17.3 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious PRR 13.1 · 84% consumer | no trial data cached |
| Limb injury | 237 | 15.1 13.3–17.1ROR 15.3 · χ² 3,073 / p <1e-300 | 14.9 EB05 13.4 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 9.3 · 84% consumer | no trial data cached |
| Injury | 231 | 5.6 4.9–6.4ROR 5.7 · χ² 867 / p 6e-191 | 5.5 EB05 4.9 · IC025 +2.2 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 4.7 | no trial data cached |
| Weight increased (weight gain) | 227 | 1.7 1.5–2.0ROR 1.8 · χ² 71 / p 1e-17 | 1.7 EB05 1.6 · IC025 +0.6 | Not in label — unassessed | serious PRR 1.3 · 74% consumer | no trial data cached |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Haemarthrosis — n=844, PRR 178.5
- Spontaneous haemorrhage — n=87, PRR 161.7
- Muscle haemorrhage — n=306, PRR 141.2
- Traumatic haemorrhage — n=122, PRR 121.7
- Tongue haemorrhage — n=58, PRR 88.4
- Mouth haemorrhage — n=226, PRR 54.2
- Haematoma muscle — n=36, PRR 53.8
- Lip haemorrhage — n=38, PRR 52.5
- Factor viii inhibition — n=29, PRR 48.1
- Mouth injury — n=28, PRR 31.9
Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.
Common questions
What are the most reported side effects of Emicizumab?
In FDA FAERS, the most frequently co-reported reaction terms for Emicizumab are haemorrhage, haemarthrosis, fall, arthralgia, epistaxis, contusion. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.
Does Emicizumab have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: THROMBOTIC MICROANGIOPATHY AND THROMBOEMBOLISM Cases of thrombotic microangiopathy and thrombotic events were reported when on average a cumulative amount of >100 U/kg/24 hours of activated prothrombin complex concentrate was administered for 24 hours or more to patients receiving HEMLIBRA prophylaxis.
Do FAERS signals prove that Emicizumab causes these side effects?
No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.
Sources & methods
- FDA label via openFDA (set ID 2483adba-fab6-4d1b-96c5-c195577ed071, effective 20250711; matched on
openfda.generic_name.exact:"EMICIZUMAB") - Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
- FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA
count=aggregation, fieldpatient.drug.openfda.generic_name.exact, 775 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction - Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
- Seriousness and sex counts from openFDA
count=serious,patient.patientsex,seriousnessdeath
Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.