Perioperative HLX10 (Serplulimab) With S-1+Oxaliplatin (SOX) in Locally Advanced and PD-L1-Positive Gastric or Esophagogastric Junction Adenocarcinoma (PLATANUS)

August 4, 2026 updated by: National Cancer Center, Japan

Perioperative HLX10 (Serplulimab) With S-1+Oxaliplatin (SOX) in Locally Advanced and PD-L1-Positive Gastric or Esophagogastric Junction Adenocarcinoma: A Randomized Phase 2 Investigator-Initiated Trial

To evaluate the clinical efficacy of perioperative treatment with S-1 + oxaliplatin (SOX)+ HLX10 compared with SOX as the control in patients with cT3-4N1-3M0 PD-L1-positive (CPS ≥ 5) locally advanced gastric adenocarcinoma or gastroesophageal junction adenocarcinoma, in a placebo-controlled, double-blind, randomized phase II investigator-initiated clinical study.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

136

Phase

  • Phase 2

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

  • Japan
    • Chiba
      • Chiba, Chiba, Japan, 260-8717
        • Recruiting
        • Chiba Cancer Center
        • Contact:
          • Keiko Minashi, M.D.
          • Phone Number: +81-43-264-5431
    • Fukuoka
      • Fukuoka, Fukuoka, Japan, 811-1395
        • Recruiting
        • Kyushu Cancer Center
        • Contact:
          • Yasue Kimura, M.D.
          • Phone Number: +81-92-541-3231
    • Gifu
      • Gifu, Gifu, Japan
        • Not yet recruiting
        • Gifu University Hospital
        • Contact:
          • Akitaka Makiyama, M.D.
          • Phone Number: +81-58-230-6000
    • Gunma
      • Maebashi, Gunma, Japan
        • Not yet recruiting
        • Gunma University Hospital
        • Contact:
          • Daisuke Takahari, M.D.
          • Phone Number: +81-27-220-7111
    • Hiroshima
      • Hiroshima, Hiroshima, Japan
        • Not yet recruiting
        • Hiroshima University Hospital
        • Contact:
          • Kazuteru Tanabe
          • Phone Number: +81-82-257-5555
    • Kanagawa
      • Kawasaki, Kanagawa, Japan
        • Recruiting
        • St. Marianna University Hospital
        • Contact:
          • Yohei Kubota, M.D.
          • Phone Number: +81-44-977-8111
      • Yokohama, Kanagawa, Japan
        • Not yet recruiting
        • Kanagawa Prefectural Hospital Organization Kanagawa Cancer Center
        • Contact:
          • Mitsuhiro Furuta, M.D.
          • Phone Number: +81-45-520-2222
    • Kitaadachi-gun
      • Ina, Kitaadachi-gun, Japan
        • Not yet recruiting
        • Saitama Prefectural Cancer Center
        • Contact:
          • Hiroki Hara, M.D.
          • Phone Number: +81-48-722-1111
    • Osaka
      • Osaka, Osaka, Japan
        • Not yet recruiting
        • Osaka International Cancer Institute
        • Contact:
          • Kazuyoshi Yamamoto, M.D.
      • Takatsuki, Osaka, Japan
        • Recruiting
        • Osaka Medical and Pharmaceutical University Hospital
        • Contact:
          • Toshifumi Yamaguchi, M.D.
          • Phone Number: +81-72-683-1221
    • Saitama
      • Hidaka, Saitama, Japan
        • Not yet recruiting
        • Saitama Medical University International Medical Center
        • Contact:
          • Shinichi Sakuramoto, M.D.
          • Phone Number: +81-42-984-4111
    • Sunto-gun
      • Nagaizumi-chō, Sunto-gun, Japan
        • Not yet recruiting
        • Shizuoka Cancer Center
        • Contact:
          • Takeshi Kawakami
          • Phone Number: +81-55-989-5222
    • Tokyo
      • Chuo Ku, Tokyo, Japan, 104-0045
      • Koto-Ku, Tokyo, Japan
        • Not yet recruiting
        • Cancer Institute Hospital of JFCR
        • Contact:
          • Akira Oki, M.D.
          • Phone Number: +81-3-3520-0111
  • South Korea
      • Songpa-dong, South Korea
        • Not yet recruiting
        • Asan Medical Center
    • Gyeonggi-do
      • Goyang-si, Gyeonggi-do, South Korea
        • Not yet recruiting
        • National Cancer Center Korea
      • Suwon, Gyeonggi-do, South Korea
        • Not yet recruiting
        • Ajou University Hospital
    • Seoul
      • Seocho, Seoul, South Korea
        • Not yet recruiting
        • Seoul St. Mary'S Hospital

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:

  • 1) Histologically confirmed gastric adenocarcinoma or gastroesophageal junction adenocarcinoma at the study site. (For gastroesophageal junction adenocarcinoma, only patients classified as Siewert type II or type III who do not require surgery involving simultaneous thoracoabdominal incision are eligible.)
  • 2) Tumor tissue determined to be PD-L1 positive (CPS >= 5) based on pre-screening evaluation by the central laboratory.
  • 3) Diagnosis of cT3-4N1-3M0 disease according to the AJCC/UICC-TNM 8th edition based on assessments performed within 28 days prior to randomization (the same day of the week 4 weeks before the randomization date is acceptable; the same applies hereafter), with no prior systemic treatment. Pre-randomization laparoscopy is not mandatory, but if performed, no non-curative factors (including liver metastasis, peritoneal metastasis, other distant metastases, or positive peritoneal cytology (CY1)) should be observed.
  • 4) Judged by the investigator as capable of undergoing R0 resection.
  • 5) Age between 18 years and 80 years on the day of enrollment.
  • 6) ECOG performance status (PS) of 0 or 1.
  • 7) The most recent laboratory values obtained within 14 days prior to randomization meet all of the following (however, transfusion, recombinant human thrombopoietin, and administration of granulocyte colony-stimulating factor (G-CSF) within 14 days prior to blood collection are not permitted): (1) Neutrophil count >= 1500/mm^3 (2) Hemoglobin >= 9.0 g/dL (3) Platelet count >= 10 x 10^4/mm^3 (4) Total bilirubin <= 1.5 mg/dL (5) AST <= 100 U/L (6) ALT <= 100 U/L (7) Serum albumin >= 3.0 g/dL (8) Serum creatinine <= 1.5 mg/dL (9) APTT <= 60 s (10) PT-INR <= 1.5
  • 8) Females of childbearing potential should test negative for pregnancy test (serum or urine) within 7 days prior to randomization (the same day of the week is acceptable).
  • 9) Male patients and females of childbearing potential agree to use contraception from the time of provision of informed consent through a specified period after the last administration of study treatment (until at least 120 days after the last dose of HLX10 and at least 180 days after the last dose of study drug other than HLX10 (S-1 or oxaliplatin)).
  • 10) Written informed consent for study participation has been obtained from the patient.

Exclusion Criteria:

  • 1) Presence of another active malignancy within 5 years prior to enrollment or concurrently. Patients with cured, localized tumors such as basal cell carcinoma of the skin, squamous cell carcinoma of the skin, superficial bladder cancer, non-invasive prostate cancer, non-invasive cervical cancer, and non-invasive breast cancer are permitted.
  • 2) Patients scheduled to undergo organ transplantation or bone marrow transplantation.
  • 3) Myocardial infarction and/or uncontrolled arrhythmia (including QTc interval >= 450 ms in males or >= 470 ms in females) occurring within 6 months prior to randomization (QTc interval calculated using Fridericia's formula).
  • 4) Cardiac dysfunction classified as NYHA Class III-IV, or left ventricular ejection fraction (LVEF) < 50 percent on echocardiography.
  • 5) Positive for any of the following: HIV antibody, HBs antigen, or HCV-RNA (HCV-RNA is measured only if HCV antibody is positive).
  • 6) HBs antigen negative, HBs antibody and/or HBc antibody positive, and quantitative HBV-DNA detectable (patients are not excluded if HBV-DNA is below the limit of detection).
  • 7) Active tuberculosis.
  • 8) Interstitial pneumonia, pneumoconiosis, radiation pneumonitis, drug-related pneumonitis, and/or severe pulmonary dysfunction that may interfere with evaluation and management of suspected drug-related pulmonary toxicity.
  • 9) Known active or suspected autoimmune disease, excluding patients whose disease is stable at randomization and who do not require systemic immunosuppressive therapy.
  • 10) Patients who received live vaccination within 28 days prior to randomization, except for inactivated virus vaccines used for seasonal influenza prophylaxis.
  • 11) Patients who require systemic corticosteroids (a therapeutic dose of > 10 mg/day prednisone or equivalent) or other immunosuppressive medications within 14 days prior to randomization or during the study period. However, in the absence of active autoimmune disease, patients are permitted to use steroids at a dose of <= 10 mg/day prednisone or equivalent, or inhaled steroids, or adrenal hormone replacement therapy.
  • 12) Patients who have an active infection requiring systemic anti-infective treatment within 14 days prior to randomization, except for prophylactic antibiotic treatment (e.g., for prevention of urinary tract infection or chronic obstructive pulmonary disease).
  • 13) Prior treatment with other antibody or drug therapies for immune checkpoint blockade, such as PD-1, PD-L1, or CTLA-4 therapy.
  • 14) Patients currently receiving other clinical study treatment, or for whom the planned start of treatment in this study is < 14 days from completion of the prior clinical study treatment.
  • 15) History of severe hypersensitivity to the monoclonal antibody or any component of the study drug.
  • 16) History of psychotropic drug abuse or drug dependence.
  • 17) Patients with a disease that may increase the risk associated with study participation and use of the study drug, or with other severe acute or chronic diseases that, in the investigator's judgment, render the patient unsuitable for participation in the study.

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: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: SOX+HLX10
Neoadjuvant treatment period: SOX+HLX10 Surgery Postoperative adjuvant treatment period: HLX10
Drug: serplulimab
Patients receive perioperative treatment with S-1 plus oxaliplatin (SOX) in combination with Serplulimab.
Other Names:
  • oxaliplatin
  • S-1 (tegafur/gimeracil/oteracil)
Placebo Comparator: SOX+Placebo
Neoadjuvant treatment period: SOX + Placebo Surgery Postoperative adjuvant treatment period: SOX
Drug: Placebo
Patients receive perioperative treatment with S-1 plus oxaliplatin (SOX) in combination with placebo.
Other Names:
  • oxaliplatin
  • S-1 (tegafur/gimeracil/oteracil)

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Pathological complete response (pCR) rate by central pathology review
Time Frame: Approximately 4-5 months after randomization (after surgery)
In the ITT population, this is defined as the proportion of subjects with complete disappearance of the tumor based on central pathology review.
Approximately 4-5 months after randomization (after surgery)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Investigator-assessed event-free survival
Time Frame: From randomization up to 28 months
In the ITT population, this is defined as the time from the date of randomization to the first occurrence of any of the following events.
From randomization up to 28 months
Overall survival
Time Frame: From randomization up to 28 months
In the ITT population, OS is defined as the time from the date of randomization to the date of death from any cause.
From randomization up to 28 months

Collaborators and Investigators

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

Sponsor

National Cancer Center, Japan

Investigators

  • Principal Investigator: Ken Kato, M.D., Ph.D., National Cancer Center, Japan

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 (Actual)

July 15, 2026

Primary Completion (Estimated)

November 30, 2028

Study Completion (Estimated)

June 30, 2029

Study Registration Dates

First Submitted

July 7, 2026

First Submitted That Met QC Criteria

July 7, 2026

First Posted (Actual)

July 13, 2026

Study Record Updates

Last Update Posted (Actual)

August 5, 2026

Last Update Submitted That Met QC Criteria

August 4, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • NCCH2414/ATLAS2502

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

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.

Subscribe