A Study of Cadonilimab Combined With Chemotherapy in People With Gastric or Gastroesophageal Junction Cancer

Inclusion criteria

• Capable of providing signed informed consent.
• Age ≥18 years at time of informed consent.
• ECOG performance status (PS) of 0 or 1 at enrollment.
• Pathologically confirmed gastric or GEJ adenocarcinoma with T1 N+ M0 or T2-4 N0-3 M0 (per AJCC 8th edition) resectable disease deemed eligible for radical surgery. A diagnostic laparoscopy is strongly recommended to confirm M0 status.
• HER2-negative tumor (IHC 0, 1+, or IHC 2+ and FISH non-amplified).
• Adequate organ and marrow function as defined below:

• Hemoglobin ≥9.0 g/dL
• Absolute neutrophil count ≥1.5 x 109/L
• Platelet count ≥100 x 109/L
• Serum bilirubin ≤1.5 x upper limit of normal (ULN). Patients with known Gilbert's disease who have bilirubin level ≤ 3 x ULN may be enrolled.
• ALT and AST ≤2.5 x ULN
• Albumin ≥2.8g/dL (albumin infusion is not allowed within 14 days before the start of treatment)
• Measured creatinine clearance >50 mL/min as determined by Cockcroft-Gault using actual body weight 7. Willing and able to undergo pre-treatment (during screening) and on-treatment tumor biopsies.

• Women of childbearing potential (as defined in Section 13.3) must have a negative serum pregnancy test within 72 hours prior to the first dose and agree to take effective contraception measures during the study drug administration and within 9 months after the last dose.

• Male patients with female partners of childbearing potential (as defined in Section 13.3) must agree to take effective contraception measures during the study drug administration and within 6 months after the last dose.

Exclusion criteria

• Histologies other than adenocarcinoma, including squamous/adenosquamous cell carcinoma, neuroendocrine, or GI stromal tumor.
• HER2-positive tumor (IHC 2+ and FISH-amplified, or IHC 3+).
• Prior anticancer treatment for the disease under study (chemotherapy, radiation therapy, chemoradiation, approved or investigational therapy) prior to initiation of study treatment.
• Prior receipt of an anti-PD1 or anti-CTLA4 monoclonal antibody, including for prior non-gastric malignancy.
• Underlying medical conditions that, in the Investigator's opinion, make the administration of cadonilimab hazardous, including but not limited to:

• Interstitial lung disease (ILD), including history of ILD or non-infectious pneumonitis.
• Active viral, bacterial, or fungal infections requiring parenteral treatment within 14 days of initiation of cadonilimab with the exception of prophylactic antibiotic treatment.
• Clinically significant cardiovascular disease, such as New York Heart Association Class II or greater cardiac disease or cerebrovascular accident within 3 months prior to initiation of study treatment, myocardial infarction within 6 months prior to initiation of study treatment, or unstable arrhythmia.
• A condition or unresolved AE from a prior investigational drug that may obscure interpretation of toxicity determination or AEs.
• History of prior solid-organ transplant, including allogeneic bone marrow transplant.
• Concurrent chronic medical condition requiring the use of supraphysiologic doses of corticosteroids (>10 mg/day of oral prednisone or equivalent) or immunosuppressive medications (absorbable topical corticosteroids not excluded).
• Any active autoimmune disease or documented history of autoimmune disease or syndrome that required systemic treatment in the past 2 years (i.e. with the use of disease-modifying agents, corticosteroids, or immunosuppressive drugs), except for vitiligo or resolved childhood asthma or atopy.

• Replacement therapy (e.g. insulin, levothyroxine) is not considered a form of systemic treatment.
• Participants with asthma who require intermittent use of bronchodilators, inhaled steroids, or local steroid injections not excluded.
• Participants with hypothyroidism stable on hormone replacement or Sjogren's syndrome not excluded.
• Known hypersensitivity to any excipient contained in the formulations of study interventions.
• Prior active malignancy active within the previous 2 years except for locally curable cancers that have been apparently cured, such as basal or squamous cell skin cancer(s), superficial bladder cancer, or carcinoma in-situ of the cervix, breast, or prostate cancer. Other cases of prior malignanices may be allowed after discussion with the Principal Investigator.
• Known HIV infection with detectable viral load. Patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial.
• Known acute hepatitis B or chronic hepatitis B infection with active untreated disease. For patients with evidence of chronic infection, the HBV viral load must be undetectable on suppressive therapy, if indicated.
• Known hepatitis C infection with detectable viral RNA. Patients with HCV infection who are currently on treatment are eligible if they have an undetectable HCV viral load.
• Receipt of a live attenuated vaccine within 30 days of study treatment initiation.