A Study to Learn About the Study Medicine Called PF-08634404 in Combination With Chemotherapy in Gastroesophageal Cancer

April 8, 2026 updated by: Pfizer

A PHASE 2/3 INTERVENTIONAL STUDY OF PF-08634404 IN COMBINATION WITH CHEMOTHERAPY IN TREATMENT-NAÏVE PARTICIPANTS WITH LOCALLY ADVANCED OR METASTATIC GASTRIC, GASTROESOPHAGEAL JUNCTION, OR ESOPHAGEAL ADENOCARCINOMA

This study is being done to learn more about a new medicine called PF-08634404 and how well it works when given with chemotherapy to people with gastroesophageal cancer that is locally advanced (spread to nearby tissues) or has spread to other parts of the body.

To join the study, participants must meet the following conditions:

Be 18 years or older. Have locally advanced or metastatic gastric, gastroesophageal junction or esophageal adenocarcinoma Be treatment naïve for advanced or metastatic disease Be in good physical condition and have healthy organs based on medical tests.

The study has two parts:

  • In the first part, researchers will check how safe the study medicine in combination with chemotherapy is and how well people respond to it.
  • In the second part, they will compare study medicine plus chemotherapy to another approved treatment (nivolumab plus chemotherapy) to see which works better.

The treatment will be given in repeated time periods called cycles.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

840

Phase

  • Phase 2
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Puerto Rico
    • United States
      • Manatí, United States, Puerto Rico, 00674
        • Not yet recruiting
        • Pan American Center for Oncology Trials, LLC - Manati Office
  • United States
    • Colorado
      • Aurora, Colorado, United States, 80012
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Boulder, Colorado, United States, 80303
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Centennial, Colorado, United States, 80112
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Colorado Springs, Colorado, United States, 80907
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Colorado Springs, Colorado, United States, 80923
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Denver, Colorado, United States, 80218
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Denver, Colorado, United States, 80220
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Englewood, Colorado, United States, 80113
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Lakewood, Colorado, United States, 80228
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Littleton, Colorado, United States, 80120
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Lone Tree, Colorado, United States, 80124
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Longmont, Colorado, United States, 80504
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Pueblo, Colorado, United States, 81003
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
      • Thornton, Colorado, United States, 80260
        • Recruiting
        • Rocky Mountain Cancer Centers, LLP
    • Illinois
      • Arlington Heights, Illinois, United States, 60005
        • Recruiting
        • Illinois Cancer Specialists
      • Bloomington, Illinois, United States, 61704
        • Recruiting
        • Illinois CancerCare - Bloomington
      • Chicago, Illinois, United States, 60631
        • Recruiting
        • Illinois Cancer Specialists
      • Galesburg, Illinois, United States, 61401
        • Recruiting
        • Illinois CancerCare - Galesburg
      • Niles, Illinois, United States, 60714
        • Recruiting
        • Illinois Cancer Specialists
      • Ottawa, Illinois, United States, 61350
        • Recruiting
        • Illinois CancerCare-Ottawa-Fox River Cancer Center
      • Pekin, Illinois, United States, 61554
        • Recruiting
        • Illinois CancerCare-Pekin
      • Peoria, Illinois, United States, 61615
        • Recruiting
        • Illinois CancerCare, P.C.
      • Peru, Illinois, United States, 61354
        • Recruiting
        • Illinois CancerCare-Peru - Valley Regional Cancer Center
      • Washington, Illinois, United States, 61571
        • Recruiting
        • Illinois CancerCare-Washington
    • Maryland
      • Annapolis, Maryland, United States, 21401
        • Recruiting
        • Maryland Oncology Hematology, P.A.
      • Bethesda, Maryland, United States, 20817
        • Recruiting
        • Maryland Oncology Hematology, P.A.
      • Brandywine, Maryland, United States, 20613
        • Recruiting
        • Maryland Oncology Hematology, P.A.
      • Columbia, Maryland, United States, 21044
        • Recruiting
        • Maryland Oncology Hematology, P.A.
      • Germantown, Maryland, United States, 20876
        • Recruiting
        • Maryland Oncology Hematology, P.A.
      • Largo, Maryland, United States, 20774
        • Recruiting
        • Maryland Oncology Hematology, P.A.
      • Rockville, Maryland, United States, 20850
        • Recruiting
        • Maryland Oncology Hematology, P.A.
      • Silver Spring, Maryland, United States, 20904
        • Recruiting
        • Maryland Oncology Hematology, P.A.
    • Nevada
      • Reno, Nevada, United States, 89502
        • Recruiting
        • Renown Regional Medical Center
      • Reno, Nevada, United States, 89502
        • Recruiting
        • Renown Health Medical Oncology
      • Reno, Nevada, United States, 89502
        • Recruiting
        • Renown Office of Clinical Research
    • Ohio
      • Cincinnati, Ohio, United States, 45245
        • Recruiting
        • Oncology Hematology Care Clinical Trials, LLC
      • Cincinnati, Ohio, United States, 45242
        • Recruiting
        • Oncology Hematology Care Clinical Trials, LLC
      • Cincinnati, Ohio, United States, 45211
        • Recruiting
        • Oncology Hematology Care Clinical Trials, LLC
      • Fairfield, Ohio, United States, 45014
        • Recruiting
        • Oncology Hematology Care Clinical Trials, LLC
    • Pennsylvania
      • Bensalem, Pennsylvania, United States, 19020
        • Recruiting
        • Alliance Cancer Specialists, PC
      • Doylestown, Pennsylvania, United States, 18901
        • Recruiting
        • Alliance Cancer Specialists, PC
      • Langhorne, Pennsylvania, United States, 19047
        • Recruiting
        • Alliance Cancer Specialists, PC
      • Media, Pennsylvania, United States, 19063
        • Recruiting
        • Alliance Cancer Specialists, PC
      • Sellersville, Pennsylvania, United States, 18960
        • Recruiting
        • Alliance Cancer Specialists, PC
      • Wynnewood, Pennsylvania, United States, 19096
        • Recruiting
        • Alliance Cancer Specialists, PC
    • Texas
      • Irving, Texas, United States, 75063
        • Recruiting
        • US Oncology Investigational Products Center (IPC)
      • Irving, Texas, United States, 75063
        • Not yet recruiting
        • US Oncology Investigational Products Center (IPC)
    • Virginia
      • Arlington, Virginia, United States, 22201
        • Not yet recruiting
        • Virginia Cancer Specialists, PC
      • Chesapeake, Virginia, United States, 23320
        • Not yet recruiting
        • Virginia Oncology Associates
      • Fairfax, Virginia, United States, 22031
        • Not yet recruiting
        • Virginia Cancer Specialists, PC
      • Hampton, Virginia, United States, 23666
        • Not yet recruiting
        • Virginia Oncology Associates
      • Manassas, Virginia, United States, 20110
        • Not yet recruiting
        • Virginia Cancer Specialists, PC
      • Newport News, Virginia, United States, 23606
        • Not yet recruiting
        • Virginia Oncology Associates
      • Norfolk, Virginia, United States, 23502
        • Not yet recruiting
        • Virginia Oncology Associates
      • Reston, Virginia, United States, 20190
        • Not yet recruiting
        • Virginia Cancer Specialists, PC
      • Virginia Beach, Virginia, United States, 23456
        • Not yet recruiting
        • Virginia Oncology Associates
      • Woodbridge, Virginia, United States, 22191
        • Not yet recruiting
        • Virginia Cancer Specialists, PC

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Histological or cytological confirmed gastric, gastroesophageal junction or esophageal adenocarcinoma.
  • Evidence of locally advanced or metastatic disease.
  • Eastern Cooperative Oncology Group performance status (ECOG) 0-1
  • No prior systemic therapy for advanced or metastatic disease.
  • Adequate hepatic, liver, and renal function
  • HER-2 negative status based on local testing
  • PD-L1 positive status based on local testing

Exclusion Criteria:

  • Participants with known active CNS metastases, including leptomeningeal, brainstem, meningeal, or spinal cord metastases or compression
  • Clinically significant risk of hemorrhage or fistula
  • Major surgery or severe trauma within 4 weeks prior to the first dose, or planned major surgery during the study
  • History of allogeneic organ transplantation and allogeneic hematopoietic stem cell transplantation.
  • Any Grade ≥3 bleeding/hemorrhage events within 28 days of Cycle 1 Day 1, or prior history of clinically significant bleeding events
  • Clinically significant cardiovascular disease, or other comorbidities, within 6 months prior to first dose
  • Participants with active autoimmune diseases requiring systemic treatment within the past 2 years
  • Evidence of non-infectious or drug-induced interstitial lung disease (ILD) pneumonitis

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Phase 2 Portion
PF-08634404 + Chemotherapy
Biological: PF-08634404
Participants will receive PF-08634404 intravenously.
Other Names:
  • SSGJ-707
Drug: Chemotherapy
Participants will receive PF-08634404 intravenously in combination with Chemotherapy.
Experimental: Phase 3: Arm A
PF-08634404 + Chemotherapy
Biological: PF-08634404
Participants will receive PF-08634404 intravenously.
Other Names:
  • SSGJ-707
Drug: Chemotherapy
Participants will receive PF-08634404 intravenously in combination with Chemotherapy.
Active Comparator: Phase 3: Arm B
Nivolumab + Chemotherapy
Drug: Chemotherapy
Participants will receive PF-08634404 intravenously in combination with Chemotherapy.
Biological: Nivolumab
Participants will receive Nivolumab intravenously.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Phase 2: Confirmed Objective response rate (ORR) using RECIST 1.1 as assessed by investigator
Time Frame: Approximately 4 years
Confirmed ORR by investigator is defined as the proportion of participants with confirmed Complete Response (CR) or Partial Response (PR) per RECIST v1.1 as assessed by investigator.
Approximately 4 years
Phase 2: Number of participants with treatment-emergent adverse events
Time Frame: Through 90 days after the last study intervention; Approximately 4 years
Adverse Events (AEs) as characterized by type, frequency, severity (as graded by NCI CTCAE version 5.0), timing, seriousness, and relationship to study intervention.
Through 90 days after the last study intervention; Approximately 4 years
Phase 3: Progression Free Survival (PFS) using RECIST 1.1 as assessed by BICR
Time Frame: Approximately 4 years
PFS by BICR is defined as the time from the date of randomization to the date of first documented disease progression per RECIST 1.1 as assessed by BICR, or death due to any cause, whichever occurs first.
Approximately 4 years
Phase 3: Overall Survival (OS)
Time Frame: Approximately 4 years
OS is defined as the time from the date of randomization to the date of death due to any cause.
Approximately 4 years

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Phase 2: Duration of Response (DOR) using RECIST 1.1 as assessed by investigator
Time Frame: Approximately 4 years
DOR by investigator is defined as the time from the first documentation of objective response (CR or PR that is subsequently confirmed) to the date of first documented disease progression per RECIST 1.1 as assessed by investigator, respectively, or death due to any cause, whichever occurs first.
Approximately 4 years
Phase 2: Progression Free Survival (PFS) using RECIST 1.1 as assessed by investigator
Time Frame: Approximately 4 years
PFS by investigator is defined as the time from the date of first dose to the date of first documented disease progression per RECIST 1.1 as assessed by investigator, or death due to any cause, whichever occurs first.
Approximately 4 years
Phase 2: Overall Survival (OS)
Time Frame: Approximately 4 years
OS is defined as the time from the date of first dose to the date of death due to any cause.
Approximately 4 years
Phase 2: Number of participants with laboratory abnormalities
Time Frame: Through 90 days after the last study intervention; Approximately 4 years
Laboratory abnormalities as characterized by type, frequency, severity (as graded by NCI CTCAE version 5.0), and timing. For laboratory tests without CTCAE grade definitions, results will be categorized as normal, high, low, or not done and be listed.
Through 90 days after the last study intervention; Approximately 4 years
Phase 2: Serum concentrations of PF-08634404
Time Frame: Approximately 21 months
Predose and postdose concentrations of PF-08634404
Approximately 21 months
Phase 2: Incidence of Anti-Drug Antibody (ADA) against PF-08634404
Time Frame: Approximately 21 months
Approximately 21 months
Phase 3: ORR using RECIST 1.1 as assessed by BICR
Time Frame: Approximately 4 years
ORR by BICR is defined as the proportion of participants with a Best Overall Response (BOR) of confirmed CR or confirmed PR per RECIST 1.1 as assessed by BICR.
Approximately 4 years
Phase 3: ORR using RECIST 1.1 as assessed by investigator
Time Frame: Approximately 4 years
ORR by investigator is defined as the proportion of participants with a BOR of confirmed CR or confirmed PR per RECIST 1.1 as assessed by investigator.
Approximately 4 years
Phase 3: Progression free survival (PFS) using RECIST 1.1 as assessed by investigator
Time Frame: Approximately 4 years
PFS by investigator is defined as the time from the date of randomization to the date of first documented disease progression per RECIST 1.1 as assessed by investigator, or death due to any cause, whichever occurs first
Approximately 4 years
Phase 3: DOR using RECIST 1.1 as assessed by BICR
Time Frame: Approximately 4 years
DOR is defined as the time from the first documentation of objective response (CR or PR that is subsequently confirmed) to the date of first documented disease progression per RECIST 1.1 as assessed by BICR, respectively, or death due to any cause, whichever occurs first.
Approximately 4 years
Phase 3: DOR using RECIST 1.1 as assessed by investigator
Time Frame: Approximately 4 years
DOR is defined as the time from the first documentation of objective response (CR or PR that is subsequently confirmed) to the date of first documented disease progression per RECIST 1.1 as assessed by investigator, respectively, or death due to any cause, whichever occurs first.
Approximately 4 years
Phase 3: PFS2 (PFS after next-line therapy) by investigator
Time Frame: Approximately 4 years
PFS2 is defined as the time from the date of randomization to the date of second objective disease progression or death due to any cause, whichever occurs first
Approximately 4 years
Phase 3: Number of participants with treatment-emergent adverse events
Time Frame: Through 90 days after the last study intervention; Approximately 4 years
AEs as characterized by type, frequency, intensity as graded by NCI CTCAE version 5.0, timing, seriousness, and relationship to study intervention(s)
Through 90 days after the last study intervention; Approximately 4 years
Phase 3: Number of participants with laboratory abnormalities
Time Frame: Through 90 days after the last study intervention; Approximately 4 years
Laboratory abnormalities as characterized by type, frequency, severity (as graded by NCI CTCAE version 5.0), and timing. For laboratory tests without CTCAE grade definitions, results will be categorized as normal, high, low, or not done and be listed.
Through 90 days after the last study intervention; Approximately 4 years
Phase 3: Serum concentrations of PF-08634404
Time Frame: Approximately 21 months
Predose and postdose concentrations of PF-08634404
Approximately 21 months
Phase 3: Incidence of ADA against PF-08634404
Time Frame: Approximately 21 months
Approximately 21 months
Phase 3: Change from baseline in Functional Assessment of Cancer Therapy - Gastric (FACT-Ga) Total score
Time Frame: Approximately 4 years
Approximately 4 years
Phase 3: Time to definitive deterioration in FACT-Ga Total score
Time Frame: Approximately 4 years
Approximately 4 years
Phase 3: Time to definitive deterioration in Gastric Cancer Subscale (GaCS) score
Time Frame: Approximately 4 years
Approximately 4 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Pfizer

Investigators

  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

April 28, 2026

Primary Completion (Estimated)

July 22, 2031

Study Completion (Estimated)

July 21, 2032

Study Registration Dates

First Submitted

January 30, 2026

First Submitted That Met QC Criteria

January 30, 2026

First Posted (Actual)

February 6, 2026

Study Record Updates

Last Update Posted (Actual)

April 13, 2026

Last Update Submitted That Met QC Criteria

April 8, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • C6461016
  • 2025-524717-86-00 (Registry Identifier: CTIS (EU))

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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