Gemtuzumab Ozogamicin side effects: what 3,635 FDA adverse event reports show

Gemtuzumab Ozogamicin · Mylotarg · 171 reaction terms · 8,235 drug–reaction co-reports · data 2026-09-14

Drug class

CD33-directed Immunoconjugate

FDA label (Established Pharmacologic Class)

Brand names

Mylotarg

openFDA label

Who reports

3,635 reports · 97% serious · 1,126 with death outcome · 47% female

openFDA FAERS counts, all years, deduplication not applied

Used for

MYLOTARG is a CD33-directed antibody and cytotoxic drug conjugate indicated for: • treatment of newly-diagnosed CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients 1 month and older ( 1.1 ). • treatment of relapsed or refractory CD33-positive AML in adults and pediatric patients 2 years and older ( 1.2 ).

FDA label, Indications and Usage

What it is

Gemtuzumab ozogamicin is an antibody-drug conjugate (ADC) composed of the CD33-directed monoclonal antibody (hP67.6; recombinant humanized immunoglobulin [Ig] G4, kappa antibody produced by mammalian cell culture in NS0 cells) that is covalently linked to the cytotoxic agent N-acetyl gamma calicheamicin.

FDA label, Description section

Boxed warning

HEPATOTOXICITY Hepatotoxicity, including severe or fatal hepatic veno-occlusive disease (VOD), also known as sinusoidal obstruction syndrome (SOS), has been reported in association with the use of MYLOTARG as a single agent, and as part of a combination chemotherapy regimen. Monitor frequently for signs and symptoms of VOD after treatment with MYLOTARG.

FDA label

How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation. Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)? That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.

Causality screen of the 40 strongest signals

Labeled — boxed warning 2Labeled adverse reaction 13Labeled (related wording) 4Likely indication confounding 1Lab value / disease marker 7Not in label — unassessed 13

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.
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. 131 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Febrile neutropenia	697	61.4 57.4–65.6ROR 75.7 · χ² 41,012 / p <1e-300	60.6 EB05 56.9 · IC025 +5.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 36.0 · 98% clinician	no trial data cached
Acute myeloid leukaemia	151	56.5 48.3–66.1ROR 58.9 · χ² 8,100 / p <1e-300	55.6 EB05 48.5 · IC025 +5.3 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 32.7 · 94% clinician	no trial data cached
Disseminated intravascular coagulation	77	31.6 25.3–39.5ROR 32.3 · χ² 2,242 / p <1e-300	31.2 EB05 25.8 · IC025 +4.3 3/3 methods agree	Not in label — unassessed	serious PRR 18.7 · 100% clinician	no trial data cached
Bone marrow failure	109	30.9 25.7–37.2ROR 31.8 · χ² 3,109 / p <1e-300	30.6 EB05 26.1 · IC025 +4.4 3/3 methods agree	Not in label — unassessed	serious PRR 18.3 · 99% clinician	no trial data cached
Blood bilirubin increased	138	29.5 25.1–34.8ROR 30.7 · χ² 3,762 / p <1e-300	29.3 EB05 25.4 · IC025 +4.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 19.3 · 100% clinician	no trial data cached
Multi-organ failure	84	27.7 22.4–34.3ROR 28.4 · χ² 2,130 / p <1e-300	27.5 EB05 22.9 · IC025 +4.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 16.4 · 96% clinician	no trial data cached
Bacteraemia	51	25.1 19.1–33.0ROR 25.4 · χ² 1,152 / p 1e-252	24.8 EB05 19.6 · IC025 +3.9 3/3 methods agree	Not in label — unassessed	serious PRR 14.7 · 98% clinician	no trial data cached
Blood alkaline phosphatase increased	105	24.4 20.2–29.5ROR 25.1 · χ² 2,330 / p <1e-300	24.3 EB05 20.6 · IC025 +4.1 3/3 methods agree	Lab value / disease marker	serious PRR 15.7 · 100% clinician	no trial data cached
Blood lactate dehydrogenase increased	65	23.6 18.5–30.1ROR 24.0 · χ² 1,380 / p <1e-300	23.4 EB05 19.0 · IC025 +3.9 3/3 methods agree	Lab value / disease marker	serious PRR 14.6 · 100% clinician	no trial data cached
Acute respiratory distress syndrome	72	23.6 18.7–29.6ROR 24.0 · χ² 1,528 / p <1e-300	23.3 EB05 19.2 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious PRR 13.8 · 98% clinician	no trial data cached
Hepatomegaly	39	22.9 16.7–31.3ROR 23.1 · χ² 791 / p 2e-174	22.6 EB05 17.2 · IC025 +3.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 13.9	no trial data cached
Aspartate aminotransferase increased	184	20.1 17.4–23.1ROR 21.1 · χ² 3,309 / p <1e-300	20.0 EB05 17.6 · IC025 +4.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 12.7 · 96% clinician	no trial data cached
Hyperbilirubinaemia	33	18.5 13.2–26.0ROR 18.7 · χ² 528 / p 3e-117	18.3 EB05 13.5 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious PRR 11.2 · ♀ 21% (drug 47%)	no trial data cached
Ascites	83	16.3 13.2–20.2ROR 16.7 · χ² 1,177 / p 4e-258	16.2 EB05 13.5 · IC025 +3.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 9.3 · 100% clinician	no trial data cached
Neutrophil count decreased	109	15.6 12.9–18.7ROR 16.0 · χ² 1,469 / p <1e-300	15.5 EB05 13.2 · IC025 +3.5 3/3 methods agree	Labeled (related wording) related wording	serious PRR 10.6 · 98% clinician	no trial data cached
Sepsis (blood infection)	299	15.5 13.9–17.3ROR 16.8 · χ² 4,050 / p <1e-300	15.4 EB05 14.0 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 9.3 · 96% clinician	no trial data cached
Alanine aminotransferase increased	163	15.3 13.2–17.8ROR 16.0 · χ² 2,172 / p <1e-300	15.3 EB05 13.4 · IC025 +3.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.1 · 90% clinician	no trial data cached
Haematocrit decreased	51	14.8 11.2–19.4ROR 15.0 · χ² 640 / p 2e-141	14.6 EB05 11.4 · IC025 +3.2 3/3 methods agree	Lab value / disease marker	serious PRR 9.9	no trial data cached
Septic shock	107	14.3 11.9–17.3ROR 14.7 · χ² 1,311 / p 2e-287	14.2 EB05 12.1 · IC025 +3.4 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 8.4 · 96% clinician	no trial data cached
Pancytopenia (all blood cells low)	133	13.8 11.7–16.3ROR 14.3 · χ² 1,566 / p <1e-300	13.7 EB05 11.8 · IC025 +3.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 8.2 · 99% clinician	no trial data cached
Mucosal inflammation	59	13.1 10.2–16.9ROR 13.3 · χ² 646 / p 9e-143	12.9 EB05 10.3 · IC025 +3.1 3/3 methods agree	Labeled (related wording) related wording	serious PRR 8.2 · 93% clinician	no trial data cached
Platelet count decreased	235	12.8 11.3–14.4ROR 13.6 · χ² 2,541 / p <1e-300	12.7 EB05 11.4 · IC025 +3.4 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 9.2 · 95% clinician	no trial data cached
Thrombocytopenia (low platelets)	239	12.4 11.0–14.0ROR 13.2 · χ² 2,499 / p <1e-300	12.3 EB05 11.1 · IC025 +3.4 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.6 · 94% clinician	no trial data cached
Hypoxia (low oxygen)	74	12.2 9.7–15.3ROR 12.4 · χ² 749 / p 3e-165	12.0 EB05 9.8 · IC025 +3.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.4 · 94% clinician	no trial data cached
Blood urea increased	35	12.0 8.6–16.7ROR 12.1 · χ² 342 / p 1e-76	11.6 EB05 8.5 · IC025 +2.8 3/3 methods agree	Lab value / disease marker	serious PRR 7.9	no trial data cached
Infusion related reaction (reaction during infusion)	130	11.4 9.6–13.5ROR 11.8 · χ² 1,221 / p 8e-268	11.2 EB05 9.7 · IC025 +3.2 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 8.2 · 98% clinician	no trial data cached
Atelectasis	19	11.3 7.2–17.7ROR 11.4 · χ² 168 / p 8e-39	10.3 EB05 6.6 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 6.8	no trial data cached
Cerebral haemorrhage	69	11.1 8.8–14.1ROR 11.3 · χ² 627 / p 1e-138	10.9 EB05 8.8 · IC025 +3.0 3/3 methods agree	Labeled (related wording) related wording	serious PRR 6.5 · 96% clinician	no trial data cached
Hepatic failure	58	11.1 8.6–14.3ROR 11.3 · χ² 522 / p 7e-116	10.8 EB05 8.5 · IC025 +2.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.6 · ♀ 19% (drug 47%) · 98% clinician	no trial data cached
Bacterial infection	34	10.6 7.6–14.8ROR 10.7 · χ² 285 / p 3e-64	10.0 EB05 7.3 · IC025 +2.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.2	no trial data cached
Platelet count increased	23	10.2 6.8–15.3ROR 10.2 · χ² 181 / p 2e-41	9.3 EB05 6.2 · IC025 +2.4 3/3 methods agree	Lab value / disease marker	serious PRR 7.6 · ♀ 100% (drug 47%)	no trial data cached
Tachypnoea	23	9.8 6.5–14.7ROR 9.9 · χ² 173 / p 8e-40	8.9 EB05 6.0 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious PRR 6.0	no trial data cached
White blood cell count decreased	184	9.8 8.5–11.3ROR 10.3 · χ² 1,450 / p <1e-300	9.7 EB05 8.5 · IC025 +3.0 3/3 methods agree	Lab value / disease marker	serious PRR 8.2 · 98% clinician	no trial data cached
Fluid overload	25	9.8 6.6–14.5ROR 9.8 · χ² 188 / p 4e-43	8.9 EB05 6.2 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 7.5 · ♀ 71% (drug 47%)	no trial data cached
Neoplasm progression	59	9.7 7.5–12.5ROR 9.9 · χ² 452 / p 1e-100	9.4 EB05 7.4 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 6.3 · 97% clinician	no trial data cached
Multiple organ dysfunction syndrome	46	9.5 7.1–12.7ROR 9.6 · χ² 342 / p 1e-76	9.1 EB05 7.0 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious PRR 5.6 · 100% clinician	no trial data cached
Coagulopathy	27	9.4 6.4–13.7ROR 9.4 · χ² 194 / p 2e-44	8.6 EB05 6.0 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 5.8	no trial data cached
Splenomegaly	18	8.9 5.6–14.1ROR 8.9 · χ² 118 / p 9e-28	7.7 EB05 5.0 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 5.9	no trial data cached
Gamma-glutamyltransferase increased	34	8.9 6.3–12.4ROR 8.9 · χ² 229 / p 5e-52	8.2 EB05 6.0 · IC025 +2.4 3/3 methods agree	Lab value / disease marker	serious PRR 5.3 · 96% clinician	no trial data cached
Pleural effusion	92	8.7 7.1–10.7ROR 8.9 · χ² 622 / p 1e-137	8.5 EB05 7.1 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 5.3 · 100% clinician	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

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
Febrile neutropenia	697	61.4 57.4–65.6ROR 75.7 · χ² 41,012 / p <1e-300	60.6 EB05 56.9 · IC025 +5.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 36.0 · 98% clinician	no trial data cached
Pyrexia (fever)	325	5.4 4.9–6.0ROR 5.9 · χ² 1,185 / p 5e-260	5.4 EB05 4.9 · IC025 +2.2 3/3 methods agree	Labeled (related wording) related wording	serious PRR 3.9 · 95% clinician	no trial data cached
Sepsis (blood infection)	299	15.5 13.9–17.3ROR 16.8 · χ² 4,050 / p <1e-300	15.4 EB05 14.0 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 9.3 · 96% clinician	no trial data cached
Thrombocytopenia (low platelets)	239	12.4 11.0–14.0ROR 13.2 · χ² 2,499 / p <1e-300	12.3 EB05 11.1 · IC025 +3.4 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.6 · 94% clinician	no trial data cached
Platelet count decreased	235	12.8 11.3–14.4ROR 13.6 · χ² 2,541 / p <1e-300	12.7 EB05 11.4 · IC025 +3.4 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 9.2 · 95% clinician	no trial data cached
Pneumonia (lung infection)	196	3.5 3.1–4.0ROR 3.6 · χ² 353 / p 6e-79	3.5 EB05 3.1 · IC025 +1.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 2.2 · 99% clinician	no trial data cached
Neutropenia (low neutrophils (infection-fighting cells))	190	8.1 7.1–9.3ROR 8.5 · χ² 1,181 / p 4e-259	8.0 EB05 7.1 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.9 · 99% clinician	no trial data cached
White blood cell count decreased	184	9.8 8.5–11.3ROR 10.3 · χ² 1,450 / p <1e-300	9.7 EB05 8.5 · IC025 +3.0 3/3 methods agree	Lab value / disease marker	serious PRR 8.2 · 98% clinician	no trial data cached
Aspartate aminotransferase increased	184	20.1 17.4–23.1ROR 21.1 · χ² 3,309 / p <1e-300	20.0 EB05 17.6 · IC025 +4.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 12.7 · 96% clinician	no trial data cached
Alanine aminotransferase increased	163	15.3 13.2–17.8ROR 16.0 · χ² 2,172 / p <1e-300	15.3 EB05 13.4 · IC025 +3.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.1 · 90% clinician	no trial data cached
Chills	158	7.8 6.7–9.1ROR 8.1 · χ² 929 / p 2e-204	7.6 EB05 6.7 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.6 · 96% clinician	no trial data cached
Acute myeloid leukaemia	151	56.5 48.3–66.1ROR 58.9 · χ² 8,100 / p <1e-300	55.6 EB05 48.5 · IC025 +5.3 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 32.7 · 94% clinician	no trial data cached
Disease progression	144	7.1 6.0–8.3ROR 7.3 · χ² 745 / p 2e-164	6.9 EB05 6.0 · IC025 +2.5 3/3 methods agree	Reporting / coding artifact	serious PRR 4.8 · 94% clinician	no trial data cached
Hypotension (low blood pressure)	142	4.1 3.5–4.8ROR 4.2 · χ² 332 / p 2e-74	4.0 EB05 3.5 · IC025 +1.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 2.8 · 96% clinician	no trial data cached
Blood bilirubin increased	138	29.5 25.1–34.8ROR 30.7 · χ² 3,762 / p <1e-300	29.3 EB05 25.4 · IC025 +4.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 19.3 · 100% clinician	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.

Disseminated intravascular coagulation — n=77, PRR 31.6
Bone marrow failure — n=109, PRR 30.9
Bacteraemia — n=51, PRR 25.1
Acute respiratory distress syndrome — n=72, PRR 23.6
Hyperbilirubinaemia — n=33, PRR 18.5
Tachypnoea — n=23, PRR 9.8
Fluid overload — n=25, PRR 9.8
Neoplasm progression — n=59, PRR 9.7
Multiple organ dysfunction syndrome — n=46, PRR 9.5
Coagulopathy — n=27, PRR 9.4

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 Gemtuzumab Ozogamicin?

In FDA FAERS, the most frequently co-reported reaction terms for Gemtuzumab Ozogamicin are febrile neutropenia, pyrexia, sepsis, thrombocytopenia, platelet count decreased, pneumonia. 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 Gemtuzumab Ozogamicin have an FDA boxed warning?

Yes. The current FDA label carries a boxed warning: HEPATOTOXICITY Hepatotoxicity, including severe or fatal hepatic veno-occlusive disease (VOD), also known as sinusoidal obstruction syndrome (SOS), has been reported in association with the use of MYLOTARG as a single agent, and as part of a combination chemotherapy regimen. Monitor frequently for signs and symptoms of VOD after treatment with MYLOTARG.

Do FAERS signals prove that Gemtuzumab Ozogamicin 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 32fd2bb2-1cfa-4250-feb8-d7956c794e05, effective 20251219; matched on openfda.generic_name.exact:"GEMTUZUMAB OZOGAMICIN")
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, field patient.drug.openfda.generic_name.exact, 171 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.