A Phase 3 interventional study of Zanidatamab and Tislelizumab in Gastric Neoplasms, Gastroesophageal Adenocarcinoma and Esophageal Adenocarcinoma, sponsored by Jazz Pharmaceuticals. Active, not recruiting at 227 sites in 33 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-20.
Sponsored by Jazz Pharmaceuticals · Phase 3, Interventional, and Treatment
This study is being done to find out if zanidatamab, when given with chemotherapy plus or minus tislelizumab, is safe and works better than trastuzumab given with chemotherapy.
The patients in this study will have advanced human epidermal growth factor 2 (HER2)-positive stomach and esophageal cancers that are no longer treatable with surgery (unresectable) or chemoradiation, and/or have grown or spread to other parts of the body (metastatic).
3,399 studies on the registry are indexed under Stomach Neoplasms; 992 are open to participants now.
This study's enrollment of 920 is above the median of 66 across 2,499 interventional studies indexed under Stomach Neoplasms.
Browse Stomach Neoplasms studies →Jazz Pharmaceuticals is the lead sponsor of 173 studies on the registry; 18 are open to participants now.
Of its 42 completed or terminated interventional studies of FDA-regulated products, 32 (76%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HER2
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
PD-1, PD-L1 and checkpoint inhibitors
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Leptomeningeal disease
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
QT and QTc
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Trastuzumab (Herceptin®) plus physician's choice of capecitabine plus oxaliplatin (CAPOX) or 5-fluorouracil (5-FU) plus cisplatin (FP)
Drug: Trastuzumab · Drug: Capecitabine · Drug: Oxaliplatin · Drug: Cisplatin · Drug: 5-Fluorouracil
Zanidatamab plus physician's choice of CAPOX or FP
Drug: Zanidatamab · Drug: Capecitabine · Drug: Oxaliplatin · Drug: Cisplatin · Drug: 5-Fluorouracil
Zanidatamab and tislelizumab plus physician's choice of CAPOX or FP
Drug: Zanidatamab · Drug: Tislelizumab · Drug: Capecitabine · Drug: Oxaliplatin · Drug: Cisplatin · Drug: 5-Fluorouracil
Administered IV
Also known as: ZW25, JZP598, ZIIHERA®
Administered IV
Administered intravenously (IV)
Also known as: Herceptin®
Administered orally (PO bid)
Administered IV
Administered IV
Administered IV
Progression-free survival (PFS) by BICR
The time from randomization to the date of documented disease progression (per Response Evaluation Criteria in Solid Tumors \[RECIST\] version 1.1) as assessed by blinded independent central review (BICR) or death from any cause
Time frame: Up to 2.5 years
Overall survival
The time from randomization to death due to any cause
Time frame: Up to 3.5 years
Confirmed objective response rate (ORR) by BICR
Number of patients who achieved a best overall response of complete response (CR) or (PR) as determined per RECIST 1.1 as assessed by BICR
Time frame: Up to 2.5 years
Duration of response (DOR) by BICR
The time from the first objective response (CR or PR) per BICR to documented progressive disease per RECIST 1.1 as assessed by BICR or death from any cause
Time frame: Up to 2.5 years
PFS per Investigator assessment
The time from randomization to the date of documented disease progression (per RECIST 1.1) as assessed by Investigator or death from any cause
Time frame: Up to 2.5 years
Confirmed ORR per Investigator assessment
Number of patients who achieved a best overall response of CR or PR as determined per RECIST 1.1 as assessed by Investigator
Time frame: Up to 2.5 years
DOR per Investigator assessment
The time from the first objective response (CR or PR) per Investigator to documented progressive disease per RECIST 1.1 as assessed by Investigator or death from any cause
Time frame: Up to 2.5 years
Assessment of Contribution of Components based on Progression-free Survival (PFS) by BICR
The time from randomization to the date of documented disease progression (per Response Evaluation Criteria in Solid Tumors \[RECIST\] version 1.1) as assessed by blinded independent central review (BICR) or death from any cause
Time frame: Up to 2.5 years
Assessment of Contribution of Components based on Overall Survival
The time from randomization to death due to any cause
Time frame: Up to 3.5 years
Incidence of adverse events
Number of subjects who experienced adverse events or serious adverse events
Time frame: Up to 2 years
Incidence of clinical laboratory abnormalities
Number of patients who experienced a maximum severity of Grade 3 or higher post-baseline laboratory abnormality, including either hematology or chemistry. Grades are defined using National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE), version 5.0
Time frame: Up to 2 years
Health-related quality of life (HRQoL) as assessed by the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (core cancer questionnaire) C30 (QLQ-C30)
Changes from baseline in the EORTC QLQ-C30 scores
Time frame: Up to 2.5 years
HRQoL as assessed by the EORTC Quality of Life Questionnaire (oesophago-gastric module) OG25 (QLQ-OG25)
Changes from baseline in the EORTC QLQ-OG25 scores
Time frame: Up to 2.5 years
HRQoL as assessed by the EuroQol 5-dimensions 5-levels (EQ-5D-5L) questionnaire
Changes from baseline in the EORTC EQ-5D-5L questionnaire scores
Time frame: Up to 2.5 years
Serum concentration of zanidatamab and tislelizumab
Time frame: Up to 2 years
Incidence of anti-drug antibodies (ADAs)
Number of patients who develop ADAs
Time frame: Up to 2 years
Showing the first 100 of 227 sites across 33 countries. Choose a country and city above to see the rest.
Plan to share: Yes — In accordance with ICMJE requirements, Jazz Pharmaceuticals may provide qualified external researchers access to individual participant data (IPD) and clinical trial data that underlie the results of this trial upon request. Qualified researchers can submit a request on https://www.jazzpharma.com/science/clinical-trial-data-sharing/ as outlined. Jazz Pharmaceuticals reserves the right not to consider a request. For inquiries about Jazz's data sharing policy contact clinicaldatasharing@jazzpharma.com.
Data sharing details ↗ · www.jazzpharma.com
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is active, not recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drugs tested here: Zanidatamab · Tislelizumab