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Vyloy

zolbetuximab-clzb
Used for Esophageal Cancer, Stomach Cancer

Vyloy (zolbetuximab or zolbetuximab-clzb) is a targeted cancer medication. It's used to treat adults with certain advanced or metastatic stomach cancer and gastroesophageal junction (GEJ) cancer. These cancers must be HER2‑negative and claudin 18.2‑positive. Vyloy (zolbetuximab) is a monoclonal antibody given as an infusion through a vein at a clinic. It's given every 2 or 3 weeks with certain chemotherapy medications. Side effects include nausea, vomiting, and low appetite.

Reviewed by:Last reviewed on January 15, 2026
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What is Vyloy (zolbetuximab)?

What is Vyloy (zolbetuximab) used for?

How Vyloy (zolbetuximab) works

Vyloy (zolbetuximab) is a claudin 18.2 (CLDN18.2)–directed monoclonal antibody. It finds the CLDN18.2 protein on stomach and GEJ cancer cells. This protein is often found in higher amounts on the cells of these types of cancers.

Once the medication finds the cancer cells, it flags these cells for your immune system to attack and kill. This can slow or stop the cancer from growing.

Drug facts

Common BrandsVyloy
Drug ClassMonoclonal antibody
Controlled Substance ClassificationNot a controlled medication
Generic StatusNo lower-cost generic available
AvailabilityPrescription only
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Side effects of Vyloy (zolbetuximab)

The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.

Common Side Effects

Note: Vyloy (zolbetuximab) is taken with certain chemotherapy medications. Your side effects might be different depending on your chemotherapy plan.

Vyloy (zolbetuximab) serious side effects

Contact your healthcare provider immediately if you experience any of the following.

  • Severe nausea or vomiting feel very nauseous, can’t keep fluids down, signs of dehydration (e.g., dizziness, exhaustion, dark urine)
  • Severe allergic reaction or infusion reaction: a cough that doesn't go away, wheezing, throat tightness, a change in your voice, trouble breathing, hives, fever, chills, nausea, vomiting, stomach pain, chest pain, back pain, high blood pressure

Source: DailyMed

The following Vyloy (zolbetuximab) side effects have also been reported

Side effects that you should report to your care team as soon as possible:

Side effects that usually do not require medical attention (report these to your care team if they continue or are bothersome):

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Pros and cons of Vyloy (zolbetuximab)

Pros

  • First targeted therapy against CLDN18.2-positive stomach cancer and GEJ cancer
  • Given every 2 or 3 weeks along with your chemotherapy, so visits can be coordinated

Cons

  • Often causes nausea and vomiting, especially with the first infusion
  • Must stay at the medical office for at least 2 extra hours after the infusion for the care team to watch for allergic reactions
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Pharmacist tips for Vyloy (zolbetuximab)

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  • Write down your appointment dates for your Vyloy (zolbetuximab) infusions. Depending on your treatment plan, they're given every 2 or 3 weeks. If you miss an appointment, call as soon as you can to reschedule.
  • Plan plenty of time for your appointment. The Vyloy (zolbetuximab) infusion takes a few hours. Then, expect to stay for at least a couple more hours afterward so your care team can watch for reactions. If you're getting your other chemotherapy medications on the same day, you'll need time for those too. Bring a snack, water, and something to do so you’re comfortable during your visit.
  • Watch for hives, coughing, chest pressure, throat tightness, or wheezing. Also watch for fever, chills, or sudden back pain. These can be signs of an infusion reaction from Vyloy (zolbetuximab). If you notice any of these symptoms during or after the infusion, tell the nurse right away so they can help you.
  • Vyloy (zolbetuximab) can make you feel very nauseous. Before each infusion, your care team will give you anti-nausea medications. If you already feel nauseous or have been vomiting, they can help manage these symptoms first.
  • If you have nausea or vomiting between Vyloy (zolbetuximab) infusions, follow your at‑home nausea plan. Keep your prescribed anti-nausea medications nearby and take them as recommended. This can help prevent “breakthrough” nausea and vomiting. Ask about other options if you need more help.
  • There are a few other ways to help manage nausea and vomiting from Vyloy (zolbetuximab). Eat small, bland meals throughout the day. Also drink plenty of fluids to help prevent dehydration.
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Risks and warnings for Vyloy (zolbetuximab)

Vyloy (zolbetuximab) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.

Serious allergic reactions (anaphylaxis and infusion reactions)

Allergic reactions can happen with Vyloy (zolbetuximab). Some reactions can be serious or even life-threatening, including anaphylaxis and infusion reactions. Your care team will watch closely for these reactions during the infusion and for at least 2 hours after.

If a reaction happens during your infusion, your care team can pause it and help treat your symptoms. Once you feel better, they might restart it at a slower speed. Before future infusions, your care team will give you an antihistamine to help prevent another reaction. If the reaction is severe, you might have to stop Vyloy (zolbetuximab) completely.

Watch for a cough that doesn't go away, wheezing, throat tightness, a change in your voice, or trouble breathing. Other symptoms include hives, fever, chills, nausea, vomiting, and stomach, chest, or back pain. If you notice any of these during or after your infusion, tell your nurse right away or get medical help.

Severe nausea and vomiting

Vyloy (zolbetuximab) can cause nausea and vomiting, which can sometimes be severe. These side effects are very common during the first treatment cycle.

Before each Vyloy (zolbetuximab) infusion, you’ll get anti‑nausea medication. Your oncologist might also give you anti-nausea medications to use at home if you need them.

Your care team can help manage nausea and vomiting. If this happens during your infusion, the nurse can pause it to help. They might also give more anti-nausea medication or IV fluids. If it's severe, your oncologist might decide to stop Vyloy (zolbetuximab) altogether.

Tell your care team right away if you feel very nauseous, can’t keep fluids down, or vomit a lot. Also call your care team if you notice signs of dehydration from these side effects, like dizziness, exhaustion, or dark urine.

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Vyloy (zolbetuximab) dosage

Typical dosage for Vyloy (zolbetuximab)

Vyloy (zolbetuximab) is given as an infusion through a vein, or an intravenous (IV) infusion. It's usually given with other chemotherapy. A nurse will help infuse the medication at a medical center or clinic.

Your oncologist will determine your dose based on your body surface area (BSA). They'll take your height and weight into account.

  • Dose 1: The typical dose is 800 mg/m² of BSA given as an IV infusion once.
  • Dose 2 and beyond: The dose can be given either every 2 or 3 weeks.
    • Every 2-week dosing: The typical dose is 400 mg/m² of BSA given IV every 2 weeks.
    • Every 3-week dosing: The typical dose is 600 mg/m² of BSA given IV every 3 weeks.

References

Best studies we found

American Cancer Society. (2024). Infusion or immune reactions.

American Cancer Society. (2025). Esophageal cancer.

Astellas Pharma US, Inc. (2025). How is VYLOY given?

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