Zolbetuximab Claudin18.2 Positive, HER2 Negative, Advanced Gastric Cancer

• Treatment effectiveness in the real world (progression-free survival, overall survival, response rate, etc.)
• Adverse effects will be evaluated according to the NCI CTCAE v5.0
• Tissue samples collected before treatment, during treatment, and at disease progression will be analyzed using multiplex IHC to assess PD-L1 expression, MMR gene status, and Claudin18.2. Additionally, NGS testing will be conducted to evaluate the correlation with the treatment response to zolbetuximab.
• Blood samples will be collected before treatment, during treatment, and after treatment completion to analyze ctDNA, scRNAseq, or immune cell profiling.

Inclusion criteria

• Patient is ≥ 19 years of age at the time of consent.
• The patient must have histologically confirmed locally advanced, unresectable, or metastatic gastric or gastroesophageal junction adenocarcinoma
• Patient whose tumor expresses CLDN18.2 in ≥ 75% of tumor cells demonstrating moderate to strong membranous CLDN18 staining as determined by local or central IHC testing.
• The tumor sample must be HER2-negative (IHC 0, 1+, or IHC 2+/ISH-).
• The patient must have received Zolbetuximab as a first-line treatment.
• 1 Patient has ECOG performance status 0 or 1.
• Patient must meet all of the following criteria based on the locally analyzed laboratory tests collected.

• Hb ≥8 g/dL (For patients who require a transfusion, it is appropriate if Hb ≥9 g/dL after transfusion)
• ANC ≥1.0 x 10^9/L
• Platelet ≥75 x 10^9/L
• Total bilirubin ≤1.5 x ULN without liver metastasis, or <3.0 x ULN if liver metastasis is present
• AST or ALT ≤2.5 x ULN without liver metastasis, or ≤5 x ULN if liver metastasis is present
• Estimated creatinine clearance ≥30 mL/min

Exclusion criteria

• Patient has previously received treatment in a clinical trial of zolbetuximab, or a clinical trial that included zolbetuximab as 1 of the treatment options, even if the patient was not given zolbetuximab
• History of known or suspected hypersensitivity to Zolbetuximab, other monoclonal antibodies, or components of the used formulations.
• Patient has received prior systemic chemotherapy for locally advanced unresectable or metastatic gastric or GEJ adenocarcinoma. However, patient may have received either neo-adjuvant or adjuvant chemotherapy, immunotherapy or other systemic anticancer therapies as long as it was completed at least 6 months prior to participation.
• Patients who have received systemic immunosuppressive therapy, including systemic corticosteroids, within 14 days before enrollment. However, patients using physiological replacement doses of hydrocortisone or its equivalent (maximum hydrocortisone 30 mg/day or prednisone 10 mg/day), those who have received a single dose of systemic corticosteroid, or those who have received systemic corticosteroids as premedication for radiologic contrast agents are allowed.
• Patient has a complete gastric outlet syndrome or a partial gastric outlet syndrome with persistent/recurrent vomiting
• Per investigator judgment, patient has significant gastric bleeding and/or untreated gastric ulcers that would exclude the patient from participation per investigator Judgment
• Patient has any other condition, which, in the opinion of the treating physician, makes the patient unsuitable to receive or tolerate zolbetuximab.