A Study of ASP2138 Together With Chemotherapy and Pembrolizumab in Adults With Gastric Cancer

A Phase 3, Global, Multi-center, Double-blind, Randomized Study of ASP2138 Plus Chemotherapy (CAPOX or mFOLFOX6) With Pembrolizumab vs Placebo Plus Chemotherapy With or Without Pembrolizumab in First-line Treatment of Locally Advanced Unresectable or Metastatic Gastric or Gastroesophageal Junction (GEJ) Adenocarcinoma in Participants Whose Tumors Are HER2-negative and Claudin (CLDN) 18.2-positive

Claudin 18.2 or CLDN18.2 is a protein found on cells in the digestive system. It is also found in some tumors. Researchers are looking at ways to attack CLDN18.2 to help control tumors. ASP2138 is thought to bind to CLDN18.2 and a type of immune cell called a T cell. This "tells" the immune system to attack the tumor. ASP2138 is a potential treatment for people with gastric cancer (also known as stomach cancer) or gastroesophageal junction cancer (GEJ cancer). GEJ is where the tube that carries food (esophagus) joins the stomach.

This study is for people with gastric or GEJ cancer that has spread nearby (locally advanced) and is not removable by surgery (unresectable), or has spread to other parts of the body (metastatic). It is for those whose cancer is human epidermal growth factor receptor 2 (HER2)-negative and CLDN18.2-positive. HER2-negative means the cancer does not have extra HER2 protein, so medicines that target HER2 do not work and are therefore not used. CLDN18.2-positive means people have a certain amount of CLDN18.2 proteins on their cancer cells. In this study, researchers want to learn if ASP2138 given together with standard treatments (chemotherapy and pembrolizumab) help people with HER2-negative and CLDN18.2-positive gastric or GEJ cancer. The main aim is to learn how long people who are given ASP2138 with chemotherapy and pembrolizumab live without their cancer getting worse, compared with placebo given with chemotherapy with or without pembrolizumab, and if they live for longer. Placebo looks like the study treatment but does not have any medicine in it.

The main aim of this study is to check how well ASP2138 works when given together with chemotherapy and pembrolizumab compared with placebo plus chemotherapy with or without pembrolizumab.

People aged 18 years or older with locally advanced unresectable or metastatic gastric or GEJ cancer can take part. Their tumor should be HER2-negative and CLDN18.2-positive. The study doctors will check people for any health conditions that can exclude them from taking part, interfere with the study procedures, or pose an unacceptable risk.

This is a double-blind study. That means the people and the study doctors will not know who will receive which treatment. People will be assigned to one of 2 treatment groups by chance:

Group A: People will receive ASP2138 along with chemotherapy and pembrolizumab. Group B: People will receive placebo along with chemotherapy, with or without pembrolizumab.

People will keep receiving treatment until their cancer gets worse, they have medical problems that require stopping treatment, or a study rule says they must stop. There will be regular safety checks. People will continue to have scans of their tumor until their cancer becomes worse.

Study Overview

• Status: Not yet recruiting
• Conditions: Gastric Adenocarcinoma; Gastroesophageal Junction (GEJ) Adenocarcinoma
• Intervention / Treatment: Drug: Pembrolizumab; Drug: Oxaliplatin; Drug: Capecitabine; Drug: ASP2138; Drug: Folinic acid; Drug: 5-FU; Drug: Placebo for ASP2138; Drug: Placebo for Pembrolizumab

• Study Type: Interventional
• Enrollment (Estimated): 570
• Phase: Phase 3

Contacts and Locations

• Study Contact: Name: Astellas Pharma Global Development Inc; Phone Number: 800-888-7704; Email: Astellas.registration@astellas.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Participant has histologically or cytologically confirmed gastric or GEJ adenocarcinoma.
• Participant has radiographically confirmed, locally advanced unresectable or metastatic disease within 28 days prior to randomization.
• Participant has predicted life expectancy >= 12 weeks.

• Female participant is not pregnant and at least 1 of the following conditions apply:

  • Not a women of childbearing potential (WOCBP)
  • WOCBP who has a negative serum pregnancy test at screening and agrees to follow the contraceptive guidance from the time of informed consent through at least 9 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention. (Note: For screening, participants with elevated serum human chorionic gonadotropin (HCG) and a demonstrated nonpregnant status through additional testing are eligible.)
• Female participant must not be breastfeeding or lactating starting at screening and throughout the investigational period, and at least 9 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention.
• Female participant must not donate ova starting at first administration of study intervention and throughout the investigational period, and for 9 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention.
• Male participant must agree to use contraception with female partner(s) of childbearing potential (including breastfeeding partner) throughout the treatment period and for 6 months after the final administration of study intervention.
• Male participant must agree to remain abstinent or use a condom with pregnant partner(s) for the duration of the pregnancy throughout the investigational period and for 6 months after the final administration of study intervention.
• Male participant must not donate sperm during the treatment period and for 6 months after the final administration of study intervention.
• Participant has radiologically evaluable disease (measurable and/or non measurable) according to RECIST V1.1, per investigator assessment, <= 28 days prior to randomization. For participants with only 1 evaluable lesion and prior radiotherapy <= 3 months before randomization, the lesion must either be outside the field of prior radiotherapy or have documented progression following radiation therapy.
• Participant's tumor is HER2-negative (HER2 immunohistochemistry (IHC) score 0+/1+ or HER2 IHC score 2+/in situ hybridization (ISH) negative) as determined by local or central testing.
• Participant has provided an formalin-fixed paraffin-embedded (FFPE) tumor sample which meets the requirements of the study as specified in the laboratory manual.
• Participant has CLDN18.2-positive tumor as determined by central testing.
• Participant has a valid programmed death-ligand 1 (PD-L1) result as determined by central testing of a tumor sample.
• Participant with known microsatellite instability-high or mismatch repair deficient status may enroll as long as their tumor expresses PD-L1 combined positive score (CPS) >= 1 as determined by central IHC testing.
• Participant has ECOG performance status 0 to 1.
• Participant must meet all of the criteria based on the centrally or locally analyzed laboratory tests collected within 14 days prior to randomization. In case of multiple central laboratory data within this period, the most recent data should be used (transfusion is allowed, but posttransfusion hemoglobin [24 hours or later following transfusion] must be >= 9 g/dL).

South Korea Specific:

• Participant is >= 19 years of age at the time of signing informed consent.

• Female participant is not pregnant and at least 1 of the following conditions apply:

  • Not a WOCBP
  • WOCBP who has a negative serum pregnancy test at screening and agrees to follow the contraceptive guidance from the time of informed consent through at least 15 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention. (Note: For screening, participants with elevated serum HCG) and a demonstrated nonpregnant status through additional testing are eligible.)
• Female participant must not be breastfeeding or lactating starting at screening and throughout the investigational period, and at least 15 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention.
• Female participant must not donate ova starting at first administration of study intervention and throughout the investigational period, and for at least 15 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention.
• Male participant must agree to use contraception with female partner(s) of childbearing potential (including breastfeeding partner) throughout the treatment period, and for 12 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention.
• Male participant must agree to remain abstinent or use a condom with pregnant partner(s) for the duration of the pregnancy throughout the investigational period and for 12 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention.
• Male participant must not donate sperm during the treatment period and for 12 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention.

Japan Specific:

• Female participant is not pregnant and at least 1 of the following conditions apply:

  • Not a WOCBP
  • WOCBP who has a negative serum pregnancy test at screening with a medical interview and agrees to follow the contraceptive guidance from the time of informed consent through at least 9 months after the final oxaliplatin administration and 6 months after the final administration of all other study intervention. (Note: For screening, participants with elevated serum HCG and a demonstrated nonpregnant status through additional testing are eligible.)

Exclusion Criteria:

• Participant has mixed histology or non-adenocarcinoma gastric or GEJ cancer.
• Participant has known active central nervous system (CNS) metastases and/or carcinomatous meningitis. Participants with previously treated brain metastases may participate provided they are radiologically stable (i.e., without evidence of progression) for at least 4 weeks by repeat imaging (note that the repeat imaging should be performed during study screening), clinically stable and without requirement of steroid treatment for at least 14 days prior to randomization.
• Participant has gastrointestinal (GI) perforation, fistulae, untreated gastric ulcers that would preclude the participant from study participation, or any arterial thromboembolic event within 6 months, or any significant GI bleeding or any significant venous thromboembolism within 3 months prior to randomization.
• Participant has a complete gastric outlet syndrome or a partial gastric outlet syndrome with persistent/recurrent vomiting.
• Participant has pre existing peripheral neuropathy > Grade 1.
• Participant has poorly controlled hypertension.

• Participant has significant cardiovascular disease, including any of the following:

  • Congestive heart failure (defined as New York Heart Association Class III or IV), myocardial infarction, unstable angina, coronary angioplasty, stenting, coronary artery bypass graft, cerebrovascular accident or hypertensive crisis within 6 months prior to randomization.
  • corrected QT (QTc) interval > 450 msec for male participants; QTc interval > 470 msec for female participants.
  • Documented history or family history of congenital long QT syndrome.
  • Cardiac arrhythmias requiring anti-arrhythmic medications (Exception: Participant with rate-controlled atrial fibrillation for > 1 month prior to randomization is eligible), obligate use of cardiac pacemaker, or a history of clinically significant ventricular arrhythmias (i.e., sustained ventricular tachycardia, ventricular fibrillation or Torsades de Pointes).
• Participant has a diagnosis of immunodeficiency or has been diagnosed with an autoimmune disease that has required systemic treatment in past 2 years (i.e., with use of disease-modifying agents, corticosteroids or immunosuppressive drugs). Participants that require replacement therapy (e.g., thyroxine (T4), insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) may be enrolled.
• Participant has psychiatric illness or social situations that would preclude study compliance.
• Participant has history of another malignancy within 3 years prior to randomization, or any evidence of residual disease from a previously diagnosed malignancy. Participants with nonmelanoma skin cancer, localized prostate cancer treated with curative intent with no evidence of progression, low-risk or very low-risk (per standard guidelines) localized prostate cancer under active surveillance/watchful waiting without intent to treat, or carcinoma in situ of any type (if complete resection was performed) are allowed.
• Participant has history of (non-infectious) pneumonitis that required steroids, current pneumonitis, or has a history of interstitial lung disease.
• Participant has known, existing uncontrolled coagulopathy. Concomitant treatment with medications that affect the coagulation cascade with an international normalized ratio (INR) > 2 (e.g., vitamin K antagonists) is not allowed.
• Participant may receive low molecular weight heparin (LMWH) (such as enoxaparin and dalteparin) and direct oral anticoagulant (DOAC) for management of deep venous thrombosis (DVT).
• Participant has a history of bleeding diathesis or recent major bleeding events (i.e. Grade >= 2 bleeding events 28 days prior to randomization).
• Participant has uncontrolled intercurrent illness.
• Participant has active infection requiring systemic therapy that has not completely resolved within 7 days prior to randomization.
• Participant is known to have human immunodeficiency virus (HIV) infection except for those with cluster of differentiation (CD) 4+ T cell counts >= 350 cells/microliter (µL) and no history of acquired immunodeficiency syndrome (AIDS)-defining opportunistic infections within the past 12 months are eligible. NOTE: Screening for HIV infection should be conducted if indicated per local requirements.

• Participant is known to have active hepatitis B (positive hepatitis B surface antigen [HBsAg]) or hepatitis C infection. Testing is required for known history of these infections or as mandated by local requirements. NOTE: Screening for these infections should be conducted if indicated per local requirements.

  • For participant who is negative for HBsAg, but hepatitis B core (HBc) antibody positive, an hepatitis B virus (HBV) DNA test will be performed and if positive the participant will be excluded.
  • Participant with positive hepatitis C virus (HCV) serology, but negative HCV RNA test results is eligible.
  • Participant treated for HCV with undetectable viral load results is eligible.
• Participant has a known history of a positive test for tuberculosis or known active tuberculosis infection. NOTE: Screening for these infections should be conducted per local requirements.
• Participant has known complete dihydropyrimidine dehydrogenase (DPD) deficiency (screening for DPD deficiency should be conducted per local requirements).
• Participant has pernicious anemia or other anemias due to vitamin B12 deficiency.
• Participant has received prior systemic chemotherapy and/or immunotherapy for locally advanced unresectable or metastatic gastric or GEJ adenocarcinoma. However, a maximum of 1 cycle of mFOLFOX6 or CAPOX with or without immunotherapy (for those participants with CPS >= 1) is allowed to be administered prior to randomization (Note: No dose modifications are allowed for the lead-in treatment). Participants may have received either neoadjuvant or adjuvant chemotherapy, immunotherapy, or other systemic anticancer therapies as long as they were completed at least 6 months prior to randomization and there was disease progression occurs at least 6 months after the last dose. Participant may have received treatment with herbal medications that have known antitumor activity > 28 days prior to randomization. NOTE: Participants must have recovered from all AEs due to previous therapies to <= Grade 1 or baseline.
• Participant has received systemic immunosuppressive therapy, including systemic corticosteroids <= 7 days prior to randomization. Participants using a physiologic replacement dose of hydrocortisone or its equivalent (defined as up to 10 mg per day of prednisone or equivalent), receiving a single dose of systemic corticosteroids or receiving systemic corticosteroids as premedication for radiologic imaging contrast use are allowed.
• Participant has had a major surgical procedure <= 28 days before randomization and has not fully recovered.
• Participant has received a CLDN18.2-targeted therapy <= 28 days or 5 half-lives (whichever is longer) prior to randomization, or participant has experienced Grade >= 3 GI toxicity after receiving a CLDN18.2-targeted therapy.
• Participant has received radiotherapy for locally advanced unresectable or metastatic gastric or GEJ adenocarcinoma <= 14 days prior to randomization and has NOT recovered from any related toxicity. A 7-day washout is permitted for palliative radiation (<= 14 days duration time for radiotherapy) to non-CNS disease.
• Participant has received prior therapy with an anti-PD-1, anti-PD-L1 or anti-PD-L2 agent, or with an agent directed to another stimulatory or coinhibitory T-cell receptor (e.g., cytotoxic T-lymphocyte-associated protein 4 [CTLA-4], OX-40, CD137) unless received in the perioperative setting.
• Participant received a live or live-attenuated vaccine within 30 days prior to randomization. NOTE: Inactivated seasonal influenza vaccines are allowed.
• Participant has received treatment with brivudine, sorivudine or their chemically related analogues within 28 days prior to randomization or within 5 half-lives of the drug, whichever is shorter.
• Participant has received any investigational therapy within 28 days prior to randomization or within 5 half-lives of the investigational medicinal product (IMP), whichever is longer.
• Participant has any condition including clinically significant disease or co-morbidity that may adversely affect the safe delivery of treatment within this study or make the participant unsuitable for study participation.
• Participant has prior severe allergic reaction; suspected, known immediate or delayed hypersensitivity; or intolerance or contraindication to any study intervention.

EU Specific:

• Participant has known complete DPD deficiency (screening for DPD deficiency should be conducted per local requirements). All participants in the EU must be tested for DPD deficiency before receiving fluoropyrimidine-based chemotherapy, in accordance with European Society for Medical Oncology and European Medicines Agency (EMA) recommendations.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: ASP2138 in combination with pembrolizumab and chemotherapy; Participants will receive ASP2138 as a subcutaneous (SC) injection either once every two weeks (Q2W) or once every three weeks (Q3W) from cycle 1 day 1 (C1D1) followed by intravenous (IV) infusion of pembrolizumab. Participants will be treated with either ASP2138 on days 1 and 22 of each cycle if receiving capecitabine and oxaliplatin (CAPOX) treatment, and on days 1, 15 and 29 of each cycle if receiving modified 5-fluorouracil, folinic acid and oxaliplatin (mFOLFOX6) treatment until discontinuation criteria are met. For all study interventions, the treatment cycle length is 42 days.	Drug: Pembrolizumab; IV Infusion; Drug: Oxaliplatin; IV Infusion; Drug: Capecitabine; Oral administration; Drug: ASP2138; SC Injection; Drug: Folinic acid; IV Infusion; Drug: 5-FU; IV Infusion or IV bolus
Placebo Comparator: Placebo for ASP2138 in combination with pembrolizumab and chemotherapy; Participants will receive placebo matching ASP2138 as a SC injection either Q2W or Q3W from C1D1 followed by IV infusion of pembrolizumab or placebo matching pembrolizumab. Participants will be treated with either placebo matching ASP2138 on days 1 and 22 of each cycle if receiving CAPOX treatment, and on days 1, 15 and 29 of each cycle if receiving mFOLFOX6 treatment until discontinuation criteria are met. For all study interventions, the treatment cycle length is 42 days.	Drug: Pembrolizumab; IV Infusion; Drug: Oxaliplatin; IV Infusion; Drug: Capecitabine; Oral administration; Drug: Folinic acid; IV Infusion; Drug: 5-FU; IV Infusion or IV bolus; Drug: Placebo for ASP2138; SC Injection; Drug: Placebo for Pembrolizumab; IV Infusion

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Overall Survival (OS)	OS is defined as the time from the date of randomization until the documented date of death from any cause.	Up to 54 months
Progression Free Survival (PFS) per Response Evaluation Criteria in Solid Tumours Version 1.1 (RECIST V1.1) by Blinded Independent Central Review (BICR)	PFS is defined as the time from the date of randomization until the date of radiographic disease progression per RECIST V1.1 by BICR or death from any cause, whichever is earlier.	Up to 54 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Objective response rate (ORR) per RECIST V1.1 by BICR	ORR is defined as the proportion of participants with a best overall response (BOR) of complete response (CR) or partial response (PR) based on RECIST V1.1 by BICR.	Up to 54 months
Disease control rate (DCR) per RECIST V1.1 by BICR	DCR is defined as the proportion of subjects with a BOR of CR, PR, or stable disease (SD) based on RECIST V1.1 by BICR.	Up to 54 months
Duration of response (DOR) per RECIST V1.1 by BICR	DOR is defined as the time from the date of the first response (CR/PR) until the date of disease progression as per RECIST V1.1 by BICR or date of death from any cause, whichever is earlier.	Up to 54 months
PFS per RECIST V1.1 by investigator assessment	PFS per investigator assessment is defined as the time from the date of randomization until the date of documented radiologic disease progression based on RECIST V1.1 by investigator assessment or until death due to any cause, whichever is earlier.	Up to 54 months
ORR per RECIST V1.1 by investigator assessment	ORR per investigator assessment is defined as the proportion of participants with a BOR of CR or PR based on RECIST V1.1.	Up to 54 months
DCR per RECIST V1.1 by investigator assessment	DCR per investigator assessment is defined as the proportion of subjects with a BOR of CR, PR, or SD based on RECIST V1.1.	Up to 54 months
DOR per RECIST V1.1 by investigator assessment	DOR per investigator assessment is defined as the time from the date of the first response (CR/PR) until the date of disease progression as per RECIST V1.1 or date of death from any cause, whichever is earlier.	Up to 54 months
Number of participants with adverse events (AEs)	An AE is any untoward medical occurrence in a patient or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavourable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of study intervention.	Up to 46 months
Number of participants with serious adverse events (SAEs)	An SAE is defined as any untoward medical occurrence that, at any dose results in death, is life threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, and other medically important events.	Up to 46 months
Number of participants with potentially clinically significant vital sign changes	Number of participants with potentially clinically significant vital sign values.	Up to 44 months
Number of participants with laboratory value abnormalities and/or AEs	Number of participants with potentially clinically significant laboratory values.	Up to 44 months
Number of participants with electrocardiogram (ECG) normals, abnormalities and/or AEs	Number of participants with potentially clinically significant ECG values.	Up to 44 months
Number of participants at each grade of Eastern Cooperative Oncology Group (ECOG) performance status	The ECOG scale will be used to assess performance status. Grades range from 0 (fully active) to 5 (dead). Negative change scores indicate an improvement. Positive scores indicate a decline in performance.	Up to 44 months
Pharmacokinetics (PK): concentration immediately prior to dosing at multiple dosing (Ctrough) of ASP2138	Ctrough will be reported from the PK serum samples collected.	Up to 45 months
Functional Assessment of Chronic Illness Therapy-General item GP5 (FACIT-GP5) Responses Over Time	FACIT-GP5 is a single item to measure the overall impact of treatment toxicity, based upon its association with the number and degree of AEs. The item "I am bothered by side effects of treatment," is rated on a 5-point scale ranging from "not at all" (0) to "very much" (4).	Up to 46 months
Patient reported outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) Responses Over Time	PRO-CTCAE questionnaire allow participants to report on the frequency severity, and interference of the side effects they experience. Selected items from the PRO CTCAE questionnaire will be used to enhance the assessment of symptomatic AEs in the study.	Up to 46 Months
Change from Baseline in Health-related Quality of Life (HRQoL) Measured by European Organisation for Research and Treatment of Cancer Quality of Life of Cancer Patients Core Questionnaire (EORTC QLQ-C30)	EORTC QLQ-C30 is a cancer-specific instrument consisting of global health status/quality of life scale; 5 functional scales (physical, role, emotional, social and cognitive); 3 symptom scales (fatigue, nausea, and vomiting and pain); and 6 single items (dyspnea, insomnia, appetite loss, constipation, diarrhea and financial difficulties). Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." For functional scales, higher scores indicate better functioning, while for symptom scales/items, higher scores indicate worse symptoms.	Baseline and up to 46 months
Change from Baseline in HRQoL measured by European Organisation for Research and Treatment of Cancer Quality of Life of Cancer Patients Oesophago-Gastric Module (EORTC QLQ OG25)	EORTC QLQ-OG25 questionnaire is a 25-item instrument that evaluates gastric and GEJ cancer-specific symptoms. This module consists of 6 scales: dysphagia (3 items), eating restrictions (4 items), reflux (2 items), odynophagia (2 items), pain and discomfort (2 items) and anxiety (2 items), as well as 10 single items: eating in front of others, dry mouth, trouble with taste, body image, trouble swallowing saliva, choked when swallowing, trouble with coughing, trouble talking, weight loss and hair loss. Each item is scored on a scale of 1 (Not at all) to 4 (Very much). Individual item scores are transformed to a 0 (no symptoms) to 100 (maximum symptom burden) scale	Baseline and up to 46 months
Change from Baseline in HRQoL measured by EQ-5D, 5-Level Questionnaire (EQ-5D-5L)	EQ-5D-5L is a standardized instrument for use as a measure of health outcome consisting of 6 items that cover 5 main scales (mobility, self-care, usual activities, pain/discomfort and anxiety/depression) and a general visual analog scale for health status. Each item is scored on a scale of 1 (no problem or none) to 5 (unable to perform activity). The VAS ranges from 0 (worst health status) and 100 (best health status).	Baseline and up to 46 months
Number of participants with anti-drug antibodies-positive against ASP2138	Number of participants with anti-drug antibodies-positive will be reported.	Up to 45 months

Collaborators and Investigators

• Sponsor: Astellas Pharma Global Development, Inc.
• Investigators: Study Director: Development Physician, Astellas Pharma Global Development, Inc.

Study record dates

Study Major Dates

• Study Start (Estimated): June 30, 2026
• Primary Completion (Estimated): February 28, 2031
• Study Completion (Estimated): February 28, 2031

Study Registration Dates

• First Submitted: June 23, 2026
• First Submitted That Met QC Criteria: June 23, 2026
• First Posted (Actual): June 29, 2026

Study Record Updates

• Last Update Posted (Actual): June 29, 2026
• Last Update Submitted That Met QC Criteria: June 23, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Claudin (CLDN) 18.2; ASP2138; Advanced Unresectable or Metastatic Gastric Adenocarcinoma; Advanced Unresectable or Metastatic Gastroesophageal Junction (GEJ) Adenocarcinoma
• Additional Relevant MeSH Terms: Neoplasms; Neoplasms by Histologic Type; Neoplasms, Glandular and Epithelial; Carcinoma; Adenocarcinoma; Organic Chemicals; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Nucleic Acids, Nucleotides, and Nucleosides; Enzymes and Coenzymes; Coordination Complexes; Deoxycytidine; Cytidine; Pyrimidine Nucleosides; Pyrimidines; Nucleosides; Formyltetrahydrofolates; Tetrahydrofolates; Folic Acid; Pterins; Pteridines; Uracil; Pyrimidinones; Coenzymes; Deoxyribonucleosides; Capecitabine; Oxaliplatin; Fluorouracil; Leucovorin; pembrolizumab
• Other Study ID Numbers: 2138-CL-0301; 2025-524557-14-00 (Ctis)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Access to anonymized individual participant level data collected during the study, in addition to study-related supporting documentation, is planned for studies conducted with approved product indications and formulations, as well as compounds terminated during development. Studies conducted with product indications or formulations that remain active in development are assessed after study completion to determine if Individual Participant Data can be shared. Further details on Astellas' data sharing policy can be found at https://www.clinicaltrials.astellas.com/transparency/.
• IPD Sharing Time Frame: Access to participant level data is offered to researchers after publication of the primary manuscript (if applicable) and is available as long as Astellas has legal authority to provide the data.
• IPD Sharing Access Criteria: Researchers must submit a proposal to conduct a scientifically relevant analysis of the study data. The research proposal is reviewed by an Independent Research Panel. If the proposal is approved, access to the study data is provided in a secure data sharing environment after receipt of a signed Data Sharing Agreement.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No