A Study to Assess the Antitumor Activity, Safety, Pharmacokinetics and Biomarkers of Zolbetuximab (IMAB362) in Participants With Claudin (CLDN) 18.2 Positive, Metastatic or Advanced Unresectable Gastric and Gastroesophageal Junction (GEJ) Adenocarcinoma and Locoregional Gastric or GEJ Adenocarcinoma

Gastric Cancer Clinical Trial

— ILUSTRO  

Official title:

A Phase 2 Study of Zolbetuximab (IMAB362) as Monotherapy and in Combination With Chemotherapy and/or Immunotherapy in Subjects With Metastatic or Locally Advanced Unresectable Gastric or Gastroesophageal Junction (GEJ) Adenocarcinoma and Locoregional Gastric or GEJ Adenocarcinoma Whose Are Claudin (CLDN) 18.2 Positive

Clinical Trial Details — Status: Recruiting

Administrative data

• NCT number: NCT03505320
• Other study ID #: 8951-CL-0103
• Secondary ID: 2017-002566-50
• Status: Recruiting
• Phase: Phase 2
• Start date: June 29, 2018
• Est. completion date: December 31, 2026

Study information

• Verified date: April 2024
• Source: Astellas Pharma Inc
• Contact: Astellas Pharma Global Development
• Phone: 800-888-7704
• Email: astellas.registration[@]astellas.com
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

The purpose of this study is to determine the Objective Response Rate (ORR) of zolbetuzimab as a single agent as assessed by an independent central reader. This study will also assess the ORR and Progression Free Survival (PFS) of zolbetuximab in combination with mFOLFOX6 (with or without Nivolumab) and in combination with pembrolizumab, assess the safety and tolerability, assess the effects on CLDN18.2 expression and assess the immunogenicity and immunomodulatory effects of zolbetuximab as a single agent and in combination with mFOLFOX6 (with or without Nivolumab) and in combination with pembrolizumab and in combination with fluorouracil, leucovorin or folinic acid, oxaliplatin and docetaxel (FLOT). This study will also evaluate the pharmacokinetics (PK) of zolbetuximab as a single agent and in combination with mFOLFOX6 (with or without Nivolumab) and in combination with pembrolizumab and in combination with fluorouracil, leucovorin or folinic acid, oxaliplatin and docetaxel (FLOT) and PK of oxaliplatin, fluorouracil (5-FU), and pembrolizumab in combination with zolbetuximab, evaluate health-Related Quality of Life (HRQoL), evaluate the Disease Control Rate (DCR), Duration of Response (DOR), PFS of zolbetuximab as a single agent, in combination with mFOLFOX6 (with or without Nivolumab) and in combination with pembrolizumab based on both investigator and independent central reader assessment, assess Overall Survival (OS) of zolbetuximab as a single agent and in combination with mFOLFOX6 and nivolumab and in combination with FLOT.

Description:

This is a study to assess the antitumor activity of zolbetuximab, an Immunoglobulin (IgG1) chimeric monoclonal antibody directed against CLDN18.2, in subjects with recurrent locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma and locoregional gastric or GEJ adenocarcinoma whose tumors are CLDN18.2 positive. For each cohort, the study consists of the following periods: pre-screening; screening; treatment; and follow-up for disease progression (or post-treatment follow-up for disease recurrence, which will be conducted for Cohort 5). In addition, there will be a survival follow-up period for Cohorts 1A, 4B, and 5 participants only. Tolerability of zolbetuximab in combination with pembrolizumab in Japanese participant(s) will be evaluated in Cohort 3A DLT assessment. Tolerability of zolbetuximab in combination with mFOLFOX6 and nivolumab in Japanese subject(s) will be evaluated in Cohort 4B, if Japanese subjects are not enrolled in the Cohort 4A DLT assessment.

Recruitment information / eligibility

• Status: Recruiting
• Enrollment: 143
• Est. completion date: December 31, 2026
• Est. primary completion date: April 30, 2025
• Accepts healthy volunteers: No
• Gender: All
• Age group: 18 Years and older

Eligibility

Inclusion Criteria:

• Female subject eligible to participate if she is not pregnant and at least one of the

following conditions applies:

• Not a woman of child-bearing potential (WOCBP) OR
• WOCBP who agrees to follow the contraceptive guidance throughout the treatment period and for at least 9 months after the final oxaliplatin administration and 6 months after the final administration of all other study drugs.
• Female subject must agree not to breastfeed starting at screening and throughout the study period, and for 6 months after the final study drug administration.
• Female subject must agree not to donate ova starting at screening and throughout the study period, and for 9 months after the final oxaliplatin administration and 6 months after the final administration of all other study drugs.
• A sexually active male subject with a female partner(s) who is of child-bearing potential must agree to use contraception during the treatment period and for at least 6 months after the final study drug administration.
• Male subject must agree not to donate sperm starting at screening and throughout the study period, and for 6 months after the final study drug administration.
• Male subject with a pregnant or breastfeeding partner(s) must agree to remain abstinent or use a condom for the duration of the pregnancy or time partner is breastfeeding throughout the study period and for 6 months after the final study drug administration.
• Subject has histologically confirmed gastric or GEJ adenocarcinoma.
• Cohorts 1-4: Subject has radiographically-confirmed, locally advanced, unresectable or metastatic disease within 28 days prior to the first dose of study treatment.
• Subject's tumor is positive for CLDN18.2 expression demonstrating moderate to strong membranous staining as determined by central IHC testing.
• Subject agrees to not participate in another interventional study while on treatment.
• Subject has ECOG performance status 0 to 1.
• Subject has predicted life expectancy = 12 weeks.
• Subject must meet all of the following criteria based on the centrally or locally analyzed laboratory tests collected within 14 days prior to the first dose of study treatment. In case of multiple central laboratory data within this period, the most recent data should be used.
• Hemoglobin (Hgb) = 9 g/dL (transfusion is allowed, but post-transfusion Hgb [24 hours or later following transfusion] must be = 9 g/dL)
• Absolute neutrophil count (ANC) = 1.5 × 109/L
• Platelets = 100 × 10^9/L
• Albumin = 2.5 g/dL
• Total bilirubin = 1.5 × upper limit of normal (ULN)
• Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) = 2.5 × ULN in subjects without liver metastases (= 5 × ULN if liver metastases are present)
• Cohorts 1-4: Estimated creatinine clearance = 30 mL/min
• Cohort 5: Serum creatinine = 1.5 × ULN, or estimated creatinine clearance = 50 mL/min for subjects with serum creatinine levels > 1.5 × ULN
• Prothrombin time/international normalized ratio and partial thromboplastin time = 1.5 × ULN (except for subjects receiving anticoagulation therapy)

Specific to Cohort 1A:

• Subject has measurable disease according to RECIST 1.1 within 28 days prior to the first dose of study treatment per investigator assessment. For subjects with only 1 evaluable lesion and prior radiotherapy = 3 months before enrollment, the lesion must either be outside the field of prior radiotherapy or must have documented progression following radiation therapy.
• Subject has disease progression on or after at least 2 prior regimens for their advanced disease, including fluoropyrimidine and platinum-containing chemotherapy, and if appropriate, HER2/neu-targeted therapy and all associated side effects have resolved to grade 1 or less.
• Subject must have an additional available tumor specimen collected within 3 months prior to the first dose of study treatment.
• Subject must be an appropriate candidate for a tumor biopsy and is amenable to undergo a tumor biopsy during the screening period (if applicable) and treatment period as indicated in the Schedule of Assessments.

Specific to Cohort 2:

• Subject has measurable disease according to RECIST 1.1 within 28 days prior to the first dose of study treatment per investigator assessment. For subjects with only 1 evaluable lesion and prior radiotherapy = 3 months before enrollment, the lesion must either be outside the field of prior radiotherapy or must have documented progression following radiation therapy.
• Subject has not received prior systemic anti-cancer therapy for their advanced disease (subject may have received neoadjuvant and/or fluorouracil-containing adjuvant chemotherapy as long as it has been completed = 6 months before the first dose of study treatment).
• Subject has a gastric or GEJ tumor that is HER2-negative as determined by local or central testing.
• Subject must have an additional available tumor specimen collected within 3 months prior to the first dose of study treatment.
• Subject must be an appropriate candidate for a tumor biopsy and is amenable to undergo a tumor biopsy during the screening period (if applicable) and treatment period as indicated in the Schedule of Assessments.

Specific to Cohort 3A:

• Subject has radiologically evaluable disease (measurable and/or non-measurable) according to RECIST 1.1, per local assessment, = 28 days prior to the first dose of study treatment. For subjects with only 1 evaluable lesion and prior radiotherapy = 3 months before enrollment, the lesion must either be outside the field of prior radiotherapy or must have documented progression following radiation therapy.
• Subject has disease progression on or after at least 2 prior regimens for their advanced disease, including fluoropyrimidine and platinum-containing chemotherapy, and if appropriate, HER2/neu-targeted therapy.
• Subject has not received prior checkpoint inhibitor therapy.

Specific to Cohort 4A and 4B:

• Subject has radiologically evaluable disease.
• Subject has not received prior systemic anti-cancer therapy for their advanced disease.
• Subject has a gastric or GEJ tumor that is HER2-negative as determined by local or central testing.
• Subject has not received prior checkpoint inhibitor therapy.

Specific to Cohort 4B Only:

• Subject must have an additional available tumor specimen collected within 3 months prior to the first dose of study treatment.
• Subject must be an appropriate candidate for a tumor biopsy and is amenable to undergo a tumor biopsy during the screening period (if applicable) and treatment period.

Specific to Cohort 5 Only:

• Subject has new histologically confirmed primary gastric or GEJ adenocarcinoma that is amenable to curative resection.
• Subject has locoregional, resectable gastric or GEJ adenocarcinoma. GEJ may include type I-III Siewert classification. Clinical stage will be determined by endoscopic ultrasound (EUS) and/or CT or MRI. Diagnostic laparoscopy may be used as per institutional guidelines and clinical practices.
• Subject meets one of the following criteria of locoregional disease by clinical TNM

staging:

• GEJ: cT2,N0 (high risk-lesions: = 3 cm, poorly differentiated), cT1b-cT2,N+ or cT3-cT4a,Any N.
• Gastric: T2 to T4a, and/or N1-3,M0.
• Subject's tumor expresses CLDN18.2 in = 75% of tumor cells demonstrating moderate to strong membranous staining as determined by central IHC testing

Exclusion Criteria:

• Subject has had prior severe allergic reaction or intolerance to known ingredients of zolbetuximab or other monoclonal antibodies, including humanized or chimeric antibodies.
• Subject has known immediate or delayed hypersensitivity or contraindication to any component of study treatment.
• Subject has received other investigational agents or devices concurrently or within 28 days prior to first dose of study treatment.
• Subject has received systemic immunosuppressive therapy, including systemic corticosteroids 14 days prior to first dose of study treatment.
• Subject has a complete gastric outlet syndrome or a partial gastric outlet syndrome with persistent recurrent vomiting.
• Subject has significant gastric bleeding and/or untreated gastric ulcers that would preclude the subject from participation.
• Subject has history of central nervous system metastases and/or carcinomatous meningitis from gastric/GEJ cancer.
• Subject has a known history of a positive test for human immunodeficiency virus (HIV) infection or known active hepatitis B (positive hepatitis B surface antigen [HBsAg]) or hepatitis C infection.
• Subject has had within 6 months prior to first dose of study treatment any of the following: unstable angina, myocardial infarction, ventricular arrhythmia requiring intervention or hospitalization for heart failure.
• Subject has active infection requiring systemic therapy that has not completely resolved within 7 days prior to the start of study treatment.
• Subject has active autoimmune disease that has required systemic treatment within the past 3 months prior to the start of study treatment.
• Subject has a clinically significant disease or co-morbidity that may adversely affect the safe delivery of treatment within this study or make the subject unsuitable for study participation.
• Subject has psychiatric illness or social situations that would preclude study compliance.
• Subject has had a major surgical procedure = 28 days before start of study treatment.
• Subject is without complete recovery from a major surgical procedure = 14 days before start of study treatment
• Subject has received radiotherapy for locally advanced unresectable or metastatic gastric or GEJ adenocarcinoma = 14 days (Cohorts 1 and 3A) and = 28 days (Cohorts 2 and 4A or 4B) prior to start of study treatment and has NOT recovered from any related toxicity.
• Subject has another malignancy, for which treatment is required.
• Cohort 2, 4 and 5 Only, subject has any of the following:
• Prior severe allergic reaction or intolerance to any component of mFOLFOX6 or FLOT chemotherapeutics in this study
• Known dihydropyrimidine dehydrogenase deficiency (DPD).
• Known peripheral neuropathy > Grade 1 (absence of deep tendon reflexes as the sole neurological abnormality does not render the subject ineligible).
• Sinusoidal obstruction syndrome, formerly known as veno-occlusive disease, if present, should be stable or improving.
• History of clinically significant ventricular arrhythmias.
• QTc interval > 450 msec for male subjects; QTc interval > 470 msec for female subjects.
• History or family history of congenital long QT syndrome.
• Cardiac arrhythmias requiring anti-arrhythmic medications (Subjects with rate controlled atrial fibrillation for > 1 month prior to first dose of study treatment are eligible).
• Cohorts 3A, 4A and 4B Only, subject has any of the following:
• Ongoing or previous autoimmune disease or interstitial lung disease, active diverticulitis or gastrointestinal ulcerative disease, or solid organ or stem cell transplant (for Cohort 4) or other uncontrolled or clinically significant medical disorders.
• Type 1 diabetes mellitus, endocrinopathies stably maintained on appropriate replacement therapy or skin disorders (e.g., vitiligo, psoriasis, or alopecia) not requiring systemic treatment are allowed.
• Known history of serious hypersensitivity reaction to a known ingredient of pembrolizumab or nivolumab.
• Cohort 4B Only: Subjects has microsatellite instability-high or mismatch repair deficient tumors.
• Cohort 5 Only, subject has either of the following:
• Subject cannot undergo curative resection per the investigator's judgment
• Subject meets the following criterion of locoregional disease by clinical TNM staging: cT1N0.

Related Conditions & MeSH terms

• Adenocarcinoma
• Gastric Cancer
• Gastro-esophageal Junction (GEJ) Cancer
• Pharmacokinetics of Fluorouracil Bolus (5-FU)
• Pharmacokinetics of Oxaliplatin
• Pharmacokinetics of Zolbetuximab
• Stomach Neoplasms

Intervention

Drug:
• zolbetuximab
Zolbetuximab will be administered as a minimum 2-hour IV infusion.
• oxaliplatin
Oxaliplatin will be administered as a 2-hour IV infusion.
• leucovorin
Leucovorin will be administered as a 2-hour IV infusion.
• fluorouracil
Fluorouracil will be administered as IV bolus over 5 to 15 minutes and continuous IV infusion over 46 to 48 hours or per institutional guidelines.
• Pembrolizumab
Pembrolizumab will be administered intravenously over 30 minutes.
• folinic acid
Folnic acid will be administered as a 2-hour IV infusion.
• nivolumab
Nivolumab will be administered intravenously according to institutional standards.
• Docetaxel
Docetaxel will be administered as a 1-hour IV infusion.

Locations

Country	Name	City	State
France	Site FR33001	Brest
France	Site FR33004	Paris
France	Site FR33003	Pessac	Nouvelle-Aquitaine
France	Site FR33002	Poitiers	Nouvelle-Aquitaine
Italy	Site IT39005	Milano
Italy	Site IT39002	Napoli
Italy	Site IT39004	Padova
Italy	Site IT39003	Pisa
Japan	Site JP81001	Chiba
Japan	Site JP81002	Tokyo
Japan	Site JP81003	Tokyo
Korea, Republic of	Site KR82002	Seongnam-si
Korea, Republic of	Site KR82001	Seoul
Taiwan	Site TW88601	Taichung
Taiwan	Site TW88602	Tainan
United States	Mass General / North Shore Can	Boston	Massachusetts
United States	University of Chicago	Chicago	Illinois
United States	Karmanos Cancer Institute	Detroit	Michigan
United States	Virginia Cancer Specialists	Fairfax	Virginia
United States	Indiana University Cancer Center	Indianapolis	Indiana
United States	The Angeles Clinic and Research Institute	Los Angeles	California
United States	Memorial Sloan Kettering Cancer Center	New York	New York
United States	Weill Cornell Medical College	New York	New York
United States	UCLA Medical Center	Santa Monica	California
United States	Sanford Cancer Center	Sioux Falls	South Dakota
United States	Georgetown Univ Hospital	Washington	District of Columbia

Sponsors (1)

Lead Sponsor	Collaborator
Astellas Pharma Global Development, Inc.

Countries where clinical trial is conducted

United States,  France,  Italy,  Japan,  Korea, Republic of,  Taiwan, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Objective Response Rate (ORR) of zolbetuximab as a single agent by central review (Cohort 1)	The ORR is defined as the proportion of participants with complete or partial objective response based on Response Evaluation Criteria in Solid Tumors (RECIST) V1.1 (assessed by an independent review committee (IRC)).	Up to 3 months
Secondary	Pharmacokinetics (PK) of zolbetuximab: Area Under the Concentration-time Curve from the Time of Dosing Extrapolated to Time Infinity (AUCinf) (Cohorts 1A, 2, 3A, 4 and 5)	AUCinf will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Area Under the Concentration-time Curve from the Time of Dosing Extrapolated to Time Infinity Percentage (AUCinf (%extrap)) (Cohorts 1A, 2, 3A, 4 and 5)	AUCinf (%extrap) will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Area Under the Concentration-time Curve from the Time of Dosing Until the Last Measurable Concentration (AUClast) (Cohorts 1A, 2, 3A, 4 and 5)	AUClast will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Area Under the Concentration-Time Curve from the Time of Dosing to the Start of the Next Dosing Interval (AUCtau) (Cohorts 1A, 2, 3A, 4 and 5)	AUCtau will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Maximum Concentration (Cmax) (Cohorts 1A, 2, 3A, 4 and 5)	Cmax will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Concentration Immediately Prior to Dosing (Ctrough) (Cohorts 1A, 2, 3A, 4 and 5)	Ctrough will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Time of Maximum Concentration (Tmax) (Cohorts 1A, 2, 3A, 4 and 5)	Tmax will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Terminal Elimination Half-life (T1/2) (Cohorts 1A, 2, 3A, 4 and 5)	T1/2 will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Time of the last measurable concentration (Tlast) (Cohorts 1A, 2, 3A, 4 and 5)	Tlast will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Clearance (CL) (Cohorts 1A, 2, 3A, 4 and 5)	CL will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of zolbetuximab: Volume of Distribution During the Terminal Phase (Vz) (Cohorts 1A, 2, 3A, 4 and 5)	Vz will be derived from the PK serum samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: AUCinf (Cohort 2)	AUCinf will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: AUCinf (%extrap) (Cohort 2)	AUCinf (%extrap) will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: AUClast (Cohort 2)	AUClast will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: Cmax (Cohort 2)	Cmax will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: Tmax (Cohort 2)	Tmax will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: T1/2 (Cohort 2)	T1/2 will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: Tlast (Cohort 2)	Tlast will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: CL (Cohort 2)	TL will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of oxaliplatin: Vz (Cohort 2)	Vz will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): AUCinf (Cohort 2)	AUCinf will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): AUCinf (%extrap) (Cohort 2)	AUCinf (%extrap) will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): AUClast (Cohort 2)	AUClast will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): Cmax (Cohort 2)	Cmax will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): Tmax (Cohort 2)	Tmax will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): T1/2 (Cohort 2)	T1/2 will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): Tlast (Cohort 2)	Tlast will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): CL (Cohort 2)	CL will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	PK of fluorouracil bolus (5-FU): Vz (Cohort 2)	Vz will be derived from the PK plasma samples collected.	Up to 16 months
Secondary	Safety and tolerability assessed by adverse events (AEs) (Cohorts 1A, 2, 3A, 4 and 5)	An AE is any untoward medical occurrence in a participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product.	Up to 16 months
Secondary	Number of participants with electrocardiogram (ECG) abnormalities and or adverse events (Cohorts 1A, 2, 3A, 4 and 5)	Number of participants with potentially clinically significant ECG values.	Up to 14 months
Secondary	Number of participants with vital signs abnormalities and or adverse events (Cohorts 1A, 2, 3A, 4 and 5)	Number of participants with potentially clinically significant vital sign values.	Up to 14 months
Secondary	Number of participants with European Cooperative Oncology Group (ECOG) performance status abnormalities and or adverse events (Cohorts 1A, 2, 3A, 4 and 5)	Number of participants with potentially clinically significant ECOG performance status values. ECOG grades 0-5, where 0 = Fully active, able to carry on all pre-disease performance without restriction; 1 = Restricted in physically strenuous activity but ambulatory and able to carry out work of a light or sedentary nature, e.g., light house work, office work; 2 = Ambulatory and capable of all self-care but unable to carry out any work activities. Up and about more than 50% of waking hours; 3 = Capable of only limited self-care, confined to bed or chair more than 50% of waking hours; 4 = Completely disabled. Cannot carry on any self-care. Totally confined to bed or chair and 5 = Dead.	Up to 14 months
Secondary	Number of participants with laboratory assessments abnormalities and or adverse events (Cohorts 1A, 2, 3A, 4 and 5)	Number of participants with potentially clinically significant laboratory values.	Up to 14 months
Secondary	Number of anti-drug antibody (ADA) Positive Participants (Cohorts 1A, 2, 3A, 4 and 5)	Immunogenicity will be measured by the number of participants that are ADA positive.	Up to 16 months
Secondary	Health Related Quality of Life (HRQoL) measured by the Quality of Life Questionnaire - Core Questionnaire (QLQ-C30) questionnaire (Cohorts 1A, 2, 3A, 4 and 5)	The EORTC-QLQ-C30 is a cancer-specific instrument consisting of 5 functional domain scales: physical, role, emotional, social and cognitive.	Up to 16 months
Secondary	HRQoL measured by the Oesophago-Gastric Module (EORTC QLQ-OG-25) questionnaire (Cohorts 1A, 2, 3A, 4 and 5)	The EORTC-QLQ-OG25 instrument evaluates GC- and GEJC-specific symptoms such as stomach discomfort, difficulties eating and swallowing and indigestion.	Up to 16 months
Secondary	HRQoL measured by the Global Pain (GP) questionnaire (Cohorts 1A, 2, 3A, 4 and 5)	The GP instrument is a single assessment of overall pain.	Up to 16 months
Secondary	HRQoL measured by the EuroQOL Five Dimensions Questionnaire 5L (EQ-5D-5L) questionnaire (Cohorts 1A, 2, 3A, 4 and 5)	The EQ-5D-5L is a standardized instrument developed by the EuroQol Group for use as a generic, preference-based measure of health outcomes. The EQ-5D-5L is a 5-item self-reported measure of functioning and wellbeing, which assesses 5 dimensions of health, including mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension comprises 5 levels (no problems, slight problems, moderate problems, severe problems, extreme problems). A unique EQ-5D-5L health state is defined by combining 1 level from each of the 5 dimensions. This questionnaire also records the respondent's self-rated health status on a vertical graduated (0 = the worst health a participant can imagine to 100 = the best health a participant can imagine) visual analogue scale. Responses to the 5 items will also be converted to a weighted health state index (utility score) based on values derived from general population samples.	Up to 16 months
Secondary	HRQoL measured by the Health Resource Utilization (HRU) questionnaire (Cohorts 1A, 2, 3A, 4 and 5)	Health resource utilization questionnaire to assess the number of office visits, hospital stays and other healthcare resource utilization that occur outside of the clinical trial.	Up to 16 months
Secondary	Disease Control Rate (DCR) of zolbetuximab as a single agent by investigator assessment (Cohort 1A)	The DCR is defined as the proportion of subjects with complete or partial objective response, or stable disease based on RECIST V1.1.	Up to 3 months
Secondary	DCR of zolbetuximab in combination with mFOLFOX6 by investigator assessment (Cohort 2)	The DCR is defined as the proportion of subjects with complete or partial objective response, or stable disease based on RECIST V1.1.	Up to 13 months
Secondary	DCR of zolbetuximab in combination with mFOLFOX6 (with nivolumab) by investigator assessment (Cohort 4)	DCR is defined as the proportion of subjects with complete or partial objective response, or stable disease based on RECIST V1.1.	up to 13 months
Secondary	DCR of zolbetuximab as a single agent by independent central reader (Cohort 1A)	The DCR is defined as the proportion of subjects with complete or partial objective response, or stable disease based on RECIST V1.1.	Up to 3 months
Secondary	DCR of zolbetuximab in combination with mFOLFOX6 by Independent central reader (Cohort 2)	The DCR is defined as the proportion of subjects with complete or partial objective response, or stable disease based on RECIST V1.1.	Up to 13 months
Secondary	Duration of Response (DOR) of zolbetuximab as a single agent by investigator assessment (Cohort 1A)	DOR is defined as the time from the date of the first response CR/PR (whichever is first recorded) to the date of radiographical progression/death or date of censoring.	Up to 3 months
Secondary	DOR of zolbetuximab in combination with mFOLFOX6 by investigator assessment (Cohort 2)	DOR is defined as the time from the date of the first response CR/PR (whichever is first recorded) to the date of radiographical progression/death or date of censoring.	Up to 13 months
Secondary	DOR of zolbetuximab in combination with mFOLFOX6 (with nivolumab) by investigator assessment (Cohort 4)	DOR is defined as the time from the date of the first response CR/PR (whichever is first recorded) to the date of radiographical progression/death or date of censoring.	up to 13 months
Secondary	DOR of zolbetuximab as a single agent by independent central reader (Cohort 1A)	DOR is defined as the time from the date of the first response CR/PR (whichever is first recorded) to the date of radiographical progression/death or date of censoring.	Up to 3 months
Secondary	DOR of zolbetuximab in combination with mFOLFOX6 by independent central reader (Cohort 2)	DOR is defined as the time from the date of the first response CR/PR (whichever is first recorded) to the date of radiographical progression/death or date of censoring.	Up to 13 months
Secondary	Progression Free Survival (PFS) of zolbetuximab as a single agent by investigator assessment (Cohort 1A)	PFS is defined as the time from date of treatment start until the date of radiological disease progression assessed by independent radiographic reviewer (IRR), or until death due to any cause.	Up to 3 months
Secondary	PFS of zolbetuximab in combination with mFOLFOX6 by investigator assessment (Cohort 2)	PFS is defined as the time from date of treatment start until the date of radiological disease progression assessed by independent radiographic reviewer (IRR), or until death due to any cause.	Up to 13 months
Secondary	PFS of zolbetuximab in combination with mFOLFOX6 (with nivolumab) by investigator assessment (Cohort 4)	PFS is defined as the time from date of treatment start until the date of radiological disease progression assessed by independent radiographic reviewer (IRR), or until death due to any cause.	up to 13 months
Secondary	PFS of zolbetuximab as a single agent by independent central review (Cohort 1A)	PFS is defined as the time from date of treatment start until the date of radiological disease progression assessed by independent radiographic reviewer (IRR), or until death due to any cause.	Up to 3 months
Secondary	PFS of zolbetuximab in combination with mFOLFOX6 by independent central review (Cohort 2)	PFS is defined as the time from date of treatment start until the date of radiological disease progression assessed by independent radiographic reviewer (IRR), or until death due to any cause.	Up to 13 months
Secondary	ORR of zolbetuximab as a single agent by investigator assessment (Cohort 1A)	The ORR is defined as the proportion of subjects with complete or partial objective response based on RECIST V1.1.	Up to 3 months
Secondary	ORR of zolbetuximab in combination with mFOLFOX6 by investigator assessment (Cohort 2)	The ORR is defined as the proportion of subjects with complete or partial objective response based on RECIST V1.1.	Up to 13 months
Secondary	ORR of zolbetuximab in combination with mFOLFOX6 (with nivolumab) by investigator assessment (Cohort 4)	The ORR is defined as the proportion of subjects with complete or partial objective response based on RECIST V1.1.	up to 13 months
Secondary	ORR of zolbetuximab in combination with mFOLFOX6 by independent central reader (Cohort 2)	The ORR is defined as the proportion of subjects with complete or partial objective response based on RECIST V1.1.	Up to 13 months
Secondary	ORR of zolbetuximab in combination with pembrolizumab by independent central reader (Cohort 3A)	The ORR is defined as the proportion of subjects with complete or partial objective response based on RECIST V1.1.	Up to 5 months
Secondary	Overall Survival (OS) of zolbetuximab as a single agent (Cohort 1A)	OS is defined as the time from the date of treatment start until the documented date of death from any cause.	Up to 7 months
Secondary	OS of zolbetuximab in combination with mFOLFOX6 and nivolumab (Cohort 4B)	OS is defined as the time from the date of treatment start until the documented date of death from any cause.	up to 56 Months
Secondary	OS of zolbetuximab in combination with FLOT (Cohort 5)	OS is defined as the time from the date of treatment start until the documented date of death from any cause.	Up to 72 months
Secondary	Percentage of participants with surgical complications (Cohort 5)	Percentage of participants with surgical complications will be reported.	Up to 8 months
Secondary	Percentage of participants with surgical mortality as defined by death within 30 days of surgery (Cohort 5)	Percentage of participants with surgical mortality as defined by death within 30 days of surgery will be reported.	Up to 30 days
Secondary	Percentage of participants able to complete preoperative chemotherapy (Cohort 5)	Percentage of participants able to complete preoperative chemotherapy will be reported.	Up to 2 months
Secondary	Percentage of participants with perioperative mortality and morbidity at 30 days and 90 days post last dose (Cohort 5)	Percentage of participants with perioperative mortality and morbidity at 30 days and 90 days post last dose will be reported.	Up to 3 months
Secondary	Percentage of participants able to start postoperative chemotherapy (Cohort 5)	Percentage of participants able to start postoperative chemotherapy will be reported.	Up to 7 months
Secondary	Percentage of participants able to complete postoperative chemotherapy (Cohort 5)	Percentage of participants able to complete postoperative chemotherapy will be reported.	Up to 9 months
Secondary	Percentage of participants with radiological response at restaging (Cohort 5)	Radiological response will include complete response and partial response.	Up to 5 months
Secondary	Percentage of subjects with pathological response (ypTNM) (Cohort 5)	Pathological response (ypTNM) will include ypCR, ypPR	Up to 5 months
Secondary	Disease-free Survival (DFS) (Cohort 5)	DFS is defined as the time from date of treatment start until the date of radiological disease recurrence or until death due to any cause, whichever is earliest.	Up to 70 months
Secondary	Minimal Residual Disease (Cohort 5)	Minimal residual disease and disease recurrence as measured by circulating tumor DNA (ctDNA) will be summarized.	Up to 37 months