Zolbetuximab

What Zolbetuximab is used for

Quoted from the “Indications and Usage” section of the FDA-approved label.

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 gastroesophageal junction (GEJ) adenocarcinoma whose tumors are claudin (CLDN) 18.2 positive as determined by an FDA-approved test […]. …

— FDA label: Vyloy, Astellas Pharma US, Inc., effective August 11, 2026. Read the full label on DailyMed →

Label quoted: the one for the most common form (injection, powder, for suspension, intravenous), Vyloy, Astellas Pharma US, Inc.; it covers 2 products in the FDA NDC Directory. The side effects, interactions, dosage and pregnancy quotes below come from this same label.

This page is not medical advice. Talk to your doctor or pharmacist before you start, stop or change any medicine.

Boxed warning

A boxed warning (“black box”) is the FDA’s strongest warning on a drug label, for serious or life-threatening risks.

The label quoted above has no boxed warning.

Zolbetuximab side effects

Quoted from the “Adverse Reactions” section of the FDA-approved label. Tell your doctor about any side effect that worries you.

The following serious adverse reactions are described elsewhere in the labeling:

• Hypersensitivity Reactions, including anaphylaxis, and infusion related reactions [see Warnings and Precautions (5.1)].
• Severe Nausea and Vomiting [see Warnings and Precautions (5.2)].

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The most common adverse reactions (≥15%) for VYLOY in combination with mFOLFOX6 or CAPOX were nausea, vomiting, fatigue, decreased appetite, diarrhea, peripheral sensory neuropathy, abdominal pain, constipation, decreased weight, hypersensitivity reactions, and pyrexia. The most common laboratory abnormalities (≥15%) for VYLOY in combination with mFOLFOX6 or CAPOX were decreased neutrophil count, decreased leucocyte count, decreased albumin, increased creatinine, decreased hemoglobin, increased glucose, decreased lymphocyte count, increased aspartate aminotransferase, decreased platelets, increased alkaline phosphatase, increased alanine aminotransferase, decreased glucose, decreased sodium, decreased phosphate, decreased potassium, and decreased magnesium (6.1). To report SUSPECTED ADVERSE REACTIONS, contact Astellas Pharma US, Inc. at 1-800-727-7003 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The pooled safety population described in the WARNINGS AND PRECAUTIONS reflect exposure to VYLOY in 533 patients at an 800 mg/m 2 initial dose followed by subsequent doses of 600 mg/m 2 every 3 weeks in combination with fluoropyrimidine- and platinum-containing chemotherapy in the SPOTLIGHT (279) and GLOW (254) studies. Among 533 patients who received VYLOY in these studies, 47% were exposed for ≥6 months and 20% were exposed for ≥12 months. In this pooled population, the most common (≥15%) adverse reactions, were nausea, vomiting, fatigue, decreased appetite, diarrhea, peripheral sensory neuropathy, abdominal pain, constipation, decreased weight, hypersensitivity reactions, and pyrexia. The most common (≥15%) laboratory abnormalities in the pooled population were decreased neutrophil count, decreased leucocyte count, decreased albumin, increased creatinine, decreased hemoglobin, increased glucose, decreased lymphocyte count, increased aspartate aminotransferase, decreased platelets, increased alkaline phosphatase, increased alanine aminotransferase, decreased glucose, decreased sodium, decreased phosphate, decreased potassium, and decreased magnesium. SPOTLIGHT The safety of VYLOY was evaluated in SPOTLIGHT in patients with locally advanced unresectable or metastatic gastric or GEJ cancer who received at least one dose of VYLOY at an 800 mg/m 2 initial dose followed by 600 mg/m 2 subsequent doses every 3 weeks in combination with mFOLFOX6 [see Clinical Studies (14)].

— FDA label: Vyloy, Astellas Pharma US, Inc., effective August 11, 2026. This is part of the section. Read the full label on DailyMed →

Zolbetuximab dosage

Quoted from the “Dosage and Administration” section of the FDA-approved label. Your own dose is the one your doctor prescribes: do not change it on your own.

• Administer by intravenous infusion only. Do not administer VYLOY as an intravenous push or bolus. (2.6)
• The recommended first dose of VYLOY is 800 mg/m 2 followed by 600 mg/m 2 every 3 weeks or 400 mg/m 2 every 2 weeks.

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(2.3) 2.1 Patient Selection Select adult patients with locally advanced unresectable or metastatic HER2-negative gastric or GEJ adenocarcinoma whose tumors are CLDN18.2 positive (defined as ≥75% of tumor cells demonstrating moderate to strong membranous CLDN18 immunohistochemical staining) for treatment with VYLOY in combination with fluoropyrimidine- and platinum-containing chemotherapy using an FDA-approved test [see Clinical Studies (14)]. Information on FDA-approved tests for the detection of CLDN18.2 is available at https://www.fda.gov/CompanionDiagnostics. 2.2 Prior to Administration If a patient is experiencing nausea and/or vomiting prior to administration of VYLOY, the symptoms should be resolved to Grade ≤1 before administering the first infusion. Premedication Prior to each infusion of VYLOY, premedicate patients with a combination of antiemetics (e.g., NK-1 receptor blockers and/or 5-HT3 receptor blockers, as well as other drugs as indicated) for the prevention of nausea and vomiting [see Warnings and Precautions (5.2)]. 2.3 Recommended Dosage Administer VYLOY in combination with fluoropyrimidine- and platinum-containing chemotherapy as follows:

• First dose: 800 mg/m 2 intravenously.
• Subsequent doses: o 600 mg/m 2 intravenously every 3 weeks, or o 400 mg/m 2 intravenously every 2 weeks.
• Continue treatment until disease progression or unacceptable toxicity. 2.4 Dosage Modifications for Adverse Reactions No dose reduction for VYLOY is recommended. Adverse reactions for VYLOY are managed by reducing the infusion rate, interruption of the infusion, withholding the dose, and/or permanently discontinuing VYLOY as described in Table 1. Table 1. Recommended Dose Modifications for VYLOY for Adverse Reactions Adverse Reaction Severity Toxicity was graded per National Cancer Institute Common Terminology Criteria for Adverse Events Version 5.0 (NCI-CTCAE v5.0). Dose Modification Hypersensitivity or Infusion-related reactions [see Warnings and Precautions (5.1)]. Grade 2
• Interrupt the infusion until Grade ≤1, then resume at a reduced infusion rate for the remaining infusion.
• Premedicate and administer the next infusion per the infusion rates in Table 2. Grade 3 Follow Grade 2 management for Grade 3 infusion-related nausea and vomiting. or 4 or anaphylaxis
• Immediately stop the infusion and permanently discontinue. 2.5 Preparation Reconstitution
• Calculate the recommended dose based on the patient’s body surface area as described in Section 2.3 to determine the total volume and number of vials needed.
• Reconstitute each vial of VYLOY to achieve a concentration of 20 mg/mL as follows: o 100 mg vial add 5 mL of Sterile Water for Injection. o 300 mg vial add 15 mL of Sterile Water for Injection.

— FDA label: Vyloy, Astellas Pharma US, Inc., effective August 11, 2026. This is part of the section. Read the full label on DailyMed →

Zolbetuximab in pregnancy

Quoted from the pregnancy part of the FDA-approved label. Ask your doctor before you take any medicine while pregnant or planning a pregnancy.

Risk Summary There are no data with VYLOY use in pregnant women to inform any drug-associated risks. Embryo-fetal toxicity was not observed in pregnant mice intravenously administered zolbetuximab-clzb [see Data]. VYLOY should only be given to a pregnant woman if the benefit outweighs the potential risk. The background risk of major birth defects and miscarriage for the indicated population is unknown.

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In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2%-4% and 15%-20%, respectively. Data Animal Data In an embryo-fetal development toxicity study, zolbetuximab-clzb was intravenously administered to pregnant mice during the period of organogenesis and did not result in embryo-fetal toxicity at doses up to 300 mg/kg (approximately 1.9 times the recommended clinical dose based on AUC). Zolbetuximab-clzb crossed the placental barrier resulting in higher fetal serum concentrations on Day 18 of gestation than maternal serum concentrations on Day 16 of gestation.

— FDA label: Vyloy, Astellas Pharma US, Inc., effective August 11, 2026. Read the full label on DailyMed →

Forms and how it is given

Companies that list this medicine

Labelers in the FDA NDC Directory: the company named on the package (maker or distributor), with the number of prescription products.

• Astellas Pharma US, Inc.2 products

FDA approval history

• BLA: Biologics License Application: how a biologic medicine (made from living cells) is approved.

Shortage status

The FDA drug shortage list does not show these products.

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Recalls

No recall linked to these products (by their NDC code) appears in the FDA enforcement reports.

Official identifiers

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Sources

1. FDA-approved label on DailyMed (National Library of Medicine) — Vyloy, Astellas Pharma US, Inc., effective August 11, 2026; via openFDA, FDA data exported October 30, 2026, retrieved October 31, 2026
2. NDC Directory (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 30, 2026, retrieved October 31, 2026
3. Drugs@FDA (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 30, 2026, retrieved October 31, 2026
4. Drug recall enforcement reports (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 27, 2026, retrieved October 31, 2026
5. Drug shortages (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 30, 2026, retrieved October 31, 2026

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