Zolbetuximab side effects: what 1,293 FDA adverse event reports show

Zolbetuximab · Vyloy · 26 reaction terms · 1,309 drug–reaction co-reports · data 2026-09-14

Drug class

Claudin 18.2-directed Cytolytic Antibody

FDA label (Established Pharmacologic Class)

Brand names

Vyloy

openFDA label

Who reports

1,293 reports · 85% serious · 160 with death outcome · 33% female

openFDA FAERS counts, all years, deduplication not applied

Used for

VYLOY, in combination with fluoropyrimidine- and platinum-containing chemotherapy, is indicated for the first-line treatment of adults with locally advanced unresectable or metastatic human epidermal growth factor receptor 2 (HER2)‑negative gastric or .

FDA label, Indications and Usage

What it is

Zolbetuximab-clzb is a chimeric (mouse/human) antibody composed of variable regions derived from mouse anti-human claudin-18 isoform 2 monoclonal antibody and constant regions derived from human IgG1.

FDA label, Description section

Boxed warning

None in the current 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 19 strongest signals

Labeled adverse reaction 7Labeled (related wording) 2Reporting / coding artifact 1Lab value / disease marker 1Not in label — unassessed 8

What the badges mean

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.
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. 7 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
Ascites	106	58.6 48.9–70.4ROR 63.8 · χ² 5,935 / p <1e-300	57.9 EB05 49.2 · IC025 +5.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 40.0 · 99% clinician	no trial data cached
Salivary hypersecretion	16	26.0 16.0–42.3ROR 26.3 · χ² 360 / p 2e-80	25.3 EB05 16.4 · IC025 +3.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 17.8	no trial data cached
Myelosuppression	54	25.8 19.9–33.5ROR 26.9 · χ² 1,262 / p 1e-276	25.5 EB05 20.3 · IC025 +3.9 3/3 methods agree	Not in label — unassessed	serious PRR 17.4 · ♀ 57% (drug 33%) · 100% clinician	no trial data cached
Gastritis	40	24.7 18.2–33.5ROR 25.5 · χ² 886 / p 5e-195	24.4 EB05 18.7 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 19.4 · 100% clinician	no trial data cached
Neutrophil count decreased	57	22.8 17.7–29.5ROR 23.9 · χ² 1,170 / p 1e-256	22.7 EB05 18.1 · IC025 +3.8 3/3 methods agree	Labeled (related wording) related wording	serious PRR 17.3 · 100% clinician	no trial data cached
Ileus	13	17.1 10.0–29.5ROR 17.3 · χ² 182 / p 1e-41	16.2 EB05 9.4 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 11.6	no trial data cached
Malignant neoplasm progression	102	16.3 13.5–19.6ROR 17.6 · χ² 1,451 / p <1e-300	16.2 EB05 13.7 · IC025 +3.6 3/3 methods agree	Reporting / coding artifact	serious PRR 11.2 · 99% clinician	no trial data cached
Feeding disorder	17	13.8 8.6–22.2ROR 14.0 · χ² 190 / p 2e-43	13.0 EB05 8.0 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 13.1	no trial data cached
Oedema	43	12.9 9.6–17.3ROR 13.3 · χ² 461 / p 2e-102	12.6 EB05 9.6 · IC025 +3.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.1 · 98% clinician	no trial data cached
Cerebral infarction	19	12.6 8.1–19.7ROR 12.8 · χ² 192 / p 7e-44	11.7 EB05 7.4 · IC025 +2.5 3/3 methods agree	Labeled (related wording) related wording	serious PRR 8.5	no trial data cached
Pneumonia aspiration	19	12.4 7.9–19.3ROR 12.5 · χ² 187 / p 6e-43	11.5 EB05 7.3 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 8.4	no trial data cached
Decreased appetite (loss of appetite)	175	12.3 10.7–14.1ROR 14.0 · χ² 1,818 / p <1e-300	12.2 EB05 10.7 · IC025 +3.3 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 12.3 · 98% clinician	no trial data cached
Palmar-plantar erythrodysaesthesia syndrome	16	11.1 6.8–18.1ROR 11.2 · χ² 137 / p 6e-32	9.8 EB05 6.0 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 9.9	no trial data cached
Nausea	499	10.3 9.6–11.0ROR 16.1 · χ² 4,323 / p <1e-300	10.2 EB05 9.5 · IC025 +3.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.4 · 98% clinician	no trial data cached
Retching	13	9.9 5.8–17.0ROR 10.0 · χ² 96 / p 7e-23	8.3 EB05 4.8 · IC025 +2.0 3/3 methods agree	Not in label — unassessed	serious PRR 9.1	no trial data cached
Taste disorder	12	9.7 5.5–17.1ROR 9.8 · χ² 85 / p 1e-20	8.0 EB05 4.6 · IC025 +1.9 3/3 methods agree	Not in label — unassessed	serious PRR 12.1	no trial data cached
Full blood count decreased	11	8.9 4.9–15.9ROR 8.9 · χ² 69 / p 5e-17	7.1 EB05 4.0 · IC025 +1.7 3/3 methods agree	Lab value / disease marker	serious PRR 8.6	no trial data cached
Interstitial lung disease	24	8.1 5.4–12.0ROR 8.2 · χ² 142 / p 6e-33	7.2 EB05 5.0 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 5.5 · 100% clinician	no trial data cached
Infusion related reaction (reaction during infusion)	28	6.9 4.8–9.9ROR 7.0 · χ² 135 / p 2e-31	6.3 EB05 4.5 · IC025 +2.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.4 · 96% 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
Nausea	499	10.3 9.6–11.0ROR 16.1 · χ² 4,323 / p <1e-300	10.2 EB05 9.5 · IC025 +3.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.4 · 98% clinician	no trial data cached
Decreased appetite (loss of appetite)	175	12.3 10.7–14.1ROR 14.0 · χ² 1,818 / p <1e-300	12.2 EB05 10.7 · IC025 +3.3 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 12.3 · 98% clinician	no trial data cached
Ascites	106	58.6 48.9–70.4ROR 63.8 · χ² 5,935 / p <1e-300	57.9 EB05 49.2 · IC025 +5.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 40.0 · 99% clinician	no trial data cached
Malignant neoplasm progression	102	16.3 13.5–19.6ROR 17.6 · χ² 1,451 / p <1e-300	16.2 EB05 13.7 · IC025 +3.6 3/3 methods agree	Reporting / coding artifact	serious PRR 11.2 · 99% clinician	no trial data cached
Neutrophil count decreased	57	22.8 17.7–29.5ROR 23.9 · χ² 1,170 / p 1e-256	22.7 EB05 18.1 · IC025 +3.8 3/3 methods agree	Labeled (related wording) related wording	serious PRR 17.3 · 100% clinician	no trial data cached
Myelosuppression	54	25.8 19.9–33.5ROR 26.9 · χ² 1,262 / p 1e-276	25.5 EB05 20.3 · IC025 +3.9 3/3 methods agree	Not in label — unassessed	serious PRR 17.4 · ♀ 57% (drug 33%) · 100% clinician	no trial data cached
Oedema	43	12.9 9.6–17.3ROR 13.3 · χ² 461 / p 2e-102	12.6 EB05 9.6 · IC025 +3.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.1 · 98% clinician	no trial data cached
Gastritis	40	24.7 18.2–33.5ROR 25.5 · χ² 886 / p 5e-195	24.4 EB05 18.7 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 19.4 · 100% clinician	no trial data cached
Infusion related reaction (reaction during infusion)	28	6.9 4.8–9.9ROR 7.0 · χ² 135 / p 2e-31	6.3 EB05 4.5 · IC025 +2.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.4 · 96% clinician	no trial data cached
Interstitial lung disease	24	8.1 5.4–12.0ROR 8.2 · χ² 142 / p 6e-33	7.2 EB05 5.0 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 5.5 · 100% clinician	no trial data cached
Pneumonia aspiration	19	12.4 7.9–19.3ROR 12.5 · χ² 187 / p 6e-43	11.5 EB05 7.3 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 8.4	no trial data cached
Cerebral infarction	19	12.6 8.1–19.7ROR 12.8 · χ² 192 / p 7e-44	11.7 EB05 7.4 · IC025 +2.5 3/3 methods agree	Labeled (related wording) related wording	serious PRR 8.5	no trial data cached
Feeding disorder	17	13.8 8.6–22.2ROR 14.0 · χ² 190 / p 2e-43	13.0 EB05 8.0 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 13.1	no trial data cached
Palmar-plantar erythrodysaesthesia syndrome	16	11.1 6.8–18.1ROR 11.2 · χ² 137 / p 6e-32	9.8 EB05 6.0 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 9.9	no trial data cached
Salivary hypersecretion	16	26.0 16.0–42.3ROR 26.3 · χ² 360 / p 2e-80	25.3 EB05 16.4 · IC025 +3.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 17.8	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.

Myelosuppression — n=54, PRR 25.8
Interstitial lung disease — n=24, PRR 8.1

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 Zolbetuximab?

In FDA FAERS, the most frequently co-reported reaction terms for Zolbetuximab are nausea, decreased appetite, ascites, neutrophil count decreased, myelosuppression, oedema. 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 Zolbetuximab have an FDA boxed warning?

No. The FDA label retrieved for Zolbetuximab has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Zolbetuximab 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 e7695a21-abb6-47ac-93f8-0ece5a9c4409, effective 20260811; matched on openfda.generic_name.exact:"ZOLBETUXIMAB")
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, 26 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.