Ado-Trastuzumab Emtansine side effects: what 8,378 FDA adverse event reports show
Drug class
Her2-targeted antibody and microtubule inhibitor conjugate
Brand names
Kadcyla
Who reports
8,378 reports · 82% serious · 1,156 with death outcome · 97% female
Used for
KADCYLA is a HER2-targeted antibody and microtubule inhibitor conjugate indicated, as a single agent, for: the treatment of patients with HER2-positive, metastatic breast cancer who previously received trastuzumab and a taxane, separately or in combination.
What it is
KADCYLA (ado-trastuzumab emtansine) is a HER2-targeted antibody-drug conjugate (ADC) which contains the humanized anti-HER2 IgG1, trastuzumab, covalently linked to the microtubule inhibitory drug DM1 (a maytansine derivative) via the stable thioether linker MCC (4-[N-maleimidomethyl] cyclohexane-1-carboxylate).
Boxed warning
HEPATOTOXICITY, CARDIAC TOXICITY, EMBRYO-FETAL TOXICITY Hepatotoxicity: Serious hepatotoxicity has been reported, including liver failure and death in patients treated with KADCYLA. Monitor serum transaminases and bilirubin prior to initiation of KADCYLA treatment and prior to each KADCYLA dose.
Causality screen of the 40 strongest signals
What the badges mean
- Labeled — boxed warning The term (or its clinical synonym) appears in the FDA boxed warning: causality is regulator-recognised and considered serious.
- Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
- 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. 965 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 |
|---|---|---|---|---|---|---|
| Hepatopulmonary syndrome | 25 | 541.2 351.2–833.8ROR 542.8 · χ² 10,616 / p <1e-300 | 331.3 EB05 236.0 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=25 · 100% clinician | no trial data cached |
| Nail bed inflammation | 38 | 339.8 242.2–476.6ROR 341.3 · χ² 10,986 / p <1e-300 | 259.8 EB05 197.6 · IC025 +5.4 3/3 methods agree | Not in label — unassessed | serious n=37 | no trial data cached |
| Her-2 positive breast cancer | 13 | 250.6 141.7–443.2ROR 251.0 · χ² 2,712 / p <1e-300 | 170.9 EB05 106.3 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial data cached |
| Spider naevus | 15 | 217.7 128.5–369.0ROR 218.1 · χ² 2,778 / p <1e-300 | 159.8 EB05 102.8 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Her2 positive breast cancer | 28 | 205.6 139.9–302.2ROR 206.3 · χ² 5,076 / p <1e-300 | 168.3 EB05 122.2 · IC025 +4.8 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=28 | no trial data cached |
| Radiation necrosis | 42 | 199.3 145.6–272.8ROR 200.3 · χ² 7,486 / p <1e-300 | 170.3 EB05 131.3 · IC025 +5.4 3/3 methods agree | Labeled (related wording) related wording | serious n=41 · 95% clinician | no trial data cached |
| Nodular regenerative hyperplasia | 52 | 197.4 149.0–261.6ROR 198.6 · χ² 9,228 / p <1e-300 | 171.4 EB05 135.8 · IC025 +5.6 3/3 methods agree | Labeled adverse reaction exact term | serious n=48 | no trial data cached |
| Pleural neoplasm | 11 | 178.6 96.9–329.2ROR 178.8 · χ² 1,650 / p <1e-300 | 129.7 EB05 77.3 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial data cached |
| Vessel puncture site bruise | 13 | 176.3 100.5–309.3ROR 176.5 · χ² 1,954 / p <1e-300 | 132.9 EB05 82.7 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Nasal mucosal disorder | 38 | 174.0 125.3–241.6ROR 174.8 · χ² 5,944 / p <1e-300 | 150.4 EB05 114.4 · IC025 +5.2 3/3 methods agree | Not in label — unassessed | serious n=38 | no trial data cached |
| Blood uric acid decreased | 28 | 152.5 104.2–223.3ROR 153.0 · χ² 3,828 / p <1e-300 | 131.1 EB05 95.2 · IC025 +4.7 3/3 methods agree | Lab value / disease marker | serious n=28 · 96% clinician | no trial data cached |
| Microvascular coronary artery disease | 12 | 151.9 84.8–271.9ROR 152.1 · χ² 1,555 / p <1e-300 | 117.0 EB05 71.3 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=12 | no trial data cached |
| Ejection fraction | 33 | 149.7 105.4–212.6ROR 150.3 · χ² 4,456 / p <1e-300 | 130.7 EB05 97.4 · IC025 +4.9 3/3 methods agree | Labeled — boxed warning exact term | serious n=33 | no trial data cached |
| Eosinophil percentage increased | 27 | 130.6 88.8–192.3ROR 131.1 · χ² 3,177 / p <1e-300 | 114.3 EB05 82.5 · IC025 +4.6 3/3 methods agree | Lab value / disease marker | serious n=27 · 96% clinician | no trial data cached |
| Metastases to skin | 48 | 123.0 92.1–164.2ROR 123.7 · χ² 5,417 / p <1e-300 | 112.1 EB05 87.9 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=48 · 91% clinician | no trial data cached |
| Streptococcal sepsis | 52 | 114.0 86.4–150.4ROR 114.7 · χ² 5,458 / p <1e-300 | 104.9 EB05 83.1 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=52 | no trial data cached |
| Hand dermatitis | 24 | 94.5 62.9–141.9ROR 94.7 · χ² 2,048 / p <1e-300 | 85.0 EB05 60.1 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=24 | no trial data cached |
| Nail dystrophy | 20 | 93.5 59.8–146.0ROR 93.7 · χ² 1,675 / p <1e-300 | 83.2 EB05 56.9 · IC025 +4.1 3/3 methods agree | Not in label — unassessed | serious n=19 | no trial data cached |
| Breast neoplasm | 35 | 88.0 62.8–123.1ROR 88.3 · χ² 2,822 / p <1e-300 | 81.3 EB05 61.1 · IC025 +4.7 3/3 methods agree | Not in label — unassessed | serious n=33 | no trial data cached |
| Tumour marker abnormal | 11 | 84.8 46.5–154.7ROR 84.9 · χ² 802 / p 1e-176 | 72.2 EB05 43.0 · IC025 +3.2 3/3 methods agree | Lab value / disease marker | serious n=11 | no trial data cached |
| Metastases to central nervous system | 409 | 82.5 74.9–90.8ROR 86.7 · χ² 31,807 / p <1e-300 | 79.6 EB05 73.3 · IC025 +6.0 3/3 methods agree | Labeled (related wording) related wording | serious PRR 55.7 | no trial data cached |
| Non-cirrhotic portal hypertension | 11 | 78.0 42.8–142.1ROR 78.1 · χ² 738 / p 1e-162 | 67.2 EB05 40.1 · IC025 +3.1 3/3 methods agree | Labeled adverse reaction exact term | serious n=11 | no trial data cached |
| Pseudomonal sepsis | 52 | 76.1 57.8–100.2ROR 76.5 · χ² 3,665 / p <1e-300 | 71.9 EB05 57.0 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=52 | no trial data cached |
| Left ventricular dilatation | 14 | 72.0 42.3–122.4ROR 72.1 · χ² 884 / p 1e-194 | 64.1 EB05 40.6 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=14 | no trial data cached |
| Hemianopia | 26 | 66.8 45.3–98.6ROR 67.0 · χ² 1,578 / p <1e-300 | 62.3 EB05 44.7 · IC025 +4.2 3/3 methods agree | Not in label — unassessed | serious n=26 · 96% clinician | no trial data cached |
| Water intoxication | 13 | 65.3 37.7–113.3ROR 65.4 · χ² 741 / p 2e-163 | 58.5 EB05 36.4 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Mean platelet volume decreased | 20 | 61.7 39.6–96.1ROR 61.8 · χ² 1,107 / p 6e-243 | 57.1 EB05 39.0 · IC025 +3.9 3/3 methods agree | Lab value / disease marker | serious n=20 | no trial data cached |
| Dental fistula | 10 | 61.2 32.7–114.6ROR 61.3 · χ² 521 / p 1e-115 | 54.0 EB05 31.3 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Breast disorder | 48 | 60.1 45.2–80.0ROR 60.4 · χ² 2,666 / p <1e-300 | 57.4 EB05 45.0 · IC025 +4.7 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=46 | no trial data cached |
| Metastases to lymph nodes | 156 | 59.6 50.9–69.7ROR 60.7 · χ² 8,718 / p <1e-300 | 57.8 EB05 50.6 · IC025 +5.4 3/3 methods agree | Not in label — unassessed | serious n=156 | no trial data cached |
| Arteriovenous malformation | 21 | 58.7 38.1–90.4ROR 58.8 · χ² 1,108 / p 4e-243 | 54.7 EB05 37.7 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=20 · 90% clinician | no trial data cached |
| Portal hypertension | 66 | 54.6 42.9–69.7ROR 55.1 · χ² 3,348 / p <1e-300 | 52.7 EB05 42.9 · IC025 +4.9 3/3 methods agree | Labeled adverse reaction exact term | serious n=63 · 97% clinician | no trial data cached |
| Breast cancer recurrent | 65 | 52.7 41.2–67.3ROR 53.1 · χ² 3,175 / p <1e-300 | 50.9 EB05 41.3 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=64 | no trial data cached |
| Lymphangiosis carcinomatosa | 21 | 51.4 33.4–79.2ROR 51.5 · χ² 968 / p 8e-213 | 48.3 EB05 33.3 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious n=20 · 95% clinician | no trial data cached |
| Radiation skin injury | 22 | 48.3 31.7–73.6ROR 48.4 · χ² 954 / p 1e-209 | 45.6 EB05 31.8 · IC025 +3.8 3/3 methods agree | Labeled (related wording) related wording | serious n=20 · 100% clinician | no trial data cached |
| Breast operation | 15 | 47.0 28.2–78.3ROR 47.1 · χ² 618 / p 1e-136 | 43.7 EB05 28.1 · IC025 +3.4 3/3 methods agree | Reporting / coding artifact | serious n=15 | no trial data cached |
| Metastases to pleura | 19 | 46.5 29.5–73.1ROR 46.6 · χ² 786 / p 4e-173 | 43.8 EB05 29.6 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=19 | no trial data cached |
| Catheter site inflammation | 10 | 46.1 24.7–86.2ROR 46.2 · χ² 390 / p 4e-87 | 41.9 EB05 24.3 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Telangiectasia | 17 | 45.5 28.1–73.4ROR 45.5 · χ² 683 / p 9e-151 | 42.7 EB05 28.2 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Vascular device infection | 79 | 44.5 35.7–55.6ROR 44.9 · χ² 3,260 / p <1e-300 | 43.3 EB05 35.9 · IC025 +4.7 3/3 methods agree | Labeled (related wording) related wording | serious n=79 | 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 |
|---|---|---|---|---|---|---|
| Disease progression | 798 | 17.0 15.9–18.2ROR 18.7 · χ² 12,017 / p <1e-300 | 16.9 EB05 16.0 · IC025 +4.0 3/3 methods agree | Reporting / coding artifact | serious PRR 12.0 | no trial data cached |
| Fatigue (tiredness) | 757 | 2.4 2.3–2.6ROR 2.6 · χ² 665 / p 5e-147 | 2.4 EB05 2.3 · IC025 +1.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.5 | no trial data cached |
| Nausea | 735 | 2.3 2.2–2.5ROR 2.5 · χ² 579 / p 3e-128 | 2.3 EB05 2.2 · IC025 +1.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.7 | no trial data cached |
| Off label use (used outside approved label) | 645 | 1.9 1.7–2.0ROR 1.9 · χ² 266 / p 3e-60 | 1.9 EB05 1.7 · IC025 +0.8 | Reporting / coding artifact | serious PRR 2.1 | no trial data cached |
| Diarrhoea (diarrhea) | 598 | 2.3 2.2–2.5ROR 2.4 · χ² 465 / p 2e-103 | 2.3 EB05 2.2 · IC025 +1.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.6 | no trial data cached |
| Death | 555 | 1.6 1.5–1.7ROR 1.7 · χ² 134 / p 3e-31 | 1.6 EB05 1.5 · IC025 +0.5 | Outcome field, not a reaction boxed warning mentions mortality | serious PRR 1.1 | no trial data cached |
| Thrombocytopenia (low platelets) | 477 | 10.7 9.8–11.7ROR 11.3 · χ² 4,210 / p <1e-300 | 10.7 EB05 9.9 · IC025 +3.3 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 7.1 · 93% clinician | no trial data cached |
| Neuropathy peripheral (nerve damage in hands/feet) | 454 | 12.1 11.0–13.2ROR 12.7 · χ² 4,596 / p <1e-300 | 12.0 EB05 11.1 · IC025 +3.4 3/3 methods agree | Labeled — boxed warning synonym match | serious PRR 7.4 | no trial data cached |
| Platelet count decreased | 435 | 10.3 9.4–11.2ROR 10.8 · χ² 3,627 / p <1e-300 | 10.2 EB05 9.4 · IC025 +3.2 3/3 methods agree | Labeled — boxed warning synonym match | serious PRR 7.6 | no trial data cached |
| Headache | 433 | 1.7 1.6–1.9ROR 1.8 · χ² 137 / p 7e-32 | 1.7 EB05 1.6 · IC025 +0.6 | Labeled adverse reaction exact term | serious PRR 2.2 | no trial data cached |
| Metastases to central nervous system | 409 | 82.5 74.9–90.8ROR 86.7 · χ² 31,807 / p <1e-300 | 79.6 EB05 73.3 · IC025 +6.0 3/3 methods agree | Labeled (related wording) related wording | serious PRR 55.7 | no trial data cached |
| Drug ineffective (drug did not work) | 406 | 0.8 0.7–0.8ROR 0.8 · χ² 29 / p 3e-8 | 0.8 EB05 0.7 · IC025 -0.5 PRR-only: not supported by EBGM or IC | Reporting / coding artifact | serious PRR 1.4 | no trial data cached |
| Vomiting | 349 | 1.9 1.7–2.1ROR 1.9 · χ² 142 / p 6e-33 | 1.9 EB05 1.7 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 1.8 | no trial data cached |
| Pyrexia (fever) | 332 | 2.4 2.2–2.7ROR 2.5 · χ² 274 / p 7e-62 | 2.4 EB05 2.2 · IC025 +1.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 1.8 | no trial data cached |
| Epistaxis (nosebleed) | 320 | 10.7 9.6–11.9ROR 11.1 · χ² 2,809 / p <1e-300 | 10.6 EB05 9.7 · IC025 +3.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 9.1 | 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.
- Hepatopulmonary syndrome — n=25, PRR 541.2
- Nail bed inflammation — n=38, PRR 339.8
- Nasal mucosal disorder — n=38, PRR 174.0
- Metastases to skin — n=48, PRR 123.0
- Streptococcal sepsis — n=52, PRR 114.0
- Hand dermatitis — n=24, PRR 94.5
- Nail dystrophy — n=20, PRR 93.5
- Breast neoplasm — n=35, PRR 88.0
- Pseudomonal sepsis — n=52, PRR 76.1
- Hemianopia — n=26, PRR 66.8
✓ A hand-written Bradford Hill causality assessment exists for this drug: Trastuzumab ↔ Cardiotoxicity / heart failure.
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 Ado-Trastuzumab Emtansine?
In FDA FAERS, the most frequently co-reported reaction terms for Ado-Trastuzumab Emtansine are fatigue, nausea, diarrhoea, thrombocytopenia, neuropathy peripheral, platelet count decreased. 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 Ado-Trastuzumab Emtansine have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: HEPATOTOXICITY, CARDIAC TOXICITY, EMBRYO-FETAL TOXICITY Hepatotoxicity: Serious hepatotoxicity has been reported, including liver failure and death in patients treated with KADCYLA. Monitor serum transaminases and bilirubin prior to initiation of KADCYLA treatment and prior to each KADCYLA dose.
Do FAERS signals prove that Ado-Trastuzumab Emtansine 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 23f3c1f4-0fc8-4804-a9e3-04cf25dd302e, effective 20260401; matched on
openfda.generic_name.exact:"ADO-TRASTUZUMAB EMTANSINE") - 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, 1,005 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.