Bemarituzumab Plus Chemotherapy and Nivolumab Versus Chemotherapy and Nivolumab for FGFR2b Overexpressed Untreated Advanced Gastric and Gastroesophageal Junction Cancer.

Inclusion Criteria

• •Adult with unresectable, locally advanced or metastatic (not amenable to curative therapy) histologically documented gastric or gastroesophageal junction adenocarcinoma
• •Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1
• •Measurable disease or non-measurable, but evaluable disease, according to Response Evaluation Criteria in Solid Tumours version 1.1 (RECIST v1.1)
• •Participant has no contraindications to nivolumab and either mFOLFOX6 or CAPOX chemotherapy as per local prescribing information. Participants in Part 1 must have no contraindications to mFOLFOX6. Participants in Part 2 with contraindications to mFOLFOX6 are permitted and may be administered the CAPOX regimen, if no contraindications for this regimen exist. Participants in Part 2 with contraindications to CAPOX are permitted and may be administered the mFOLFOX6 regimen, if no contraindications for this regimen exist
• •Adequate organ function as follows:
• •* Absolute neutrophil count ≥ 1.5 x 10\^9/L
• •* Platelet count ≥ 100 x 10\^9/L
• •* Hemoglobin ≥ 9 g/dL without red blood cell (RBC) transfusion within 7 days prior to the first dose of study treatment
• •* Aspartate aminotransaminase (AST) and Alanine aminotransaminase (ALT) \<3 x upper limit of normal (ULN) (or \< 5 x ULN if liver involvement)
• •* Total bilirubin \<1.5 x ULN (or \< 2 x ULN if liver involvement or Gilbert's disease)
• •* Part 1 only: Calculated or measured creatinine clearance (CrCl) of ≥ 50 mL/minute calculated using the formula of Cockcroft and Gault (\[140 - Age\] × Mass \[kg\]/\[72 × Creatinine mg/dL\]) (x 0.85 if female).
• •Part 2 only: Calculated or measured creatinine clearance (CrCl) of ≥ 30 mL/minute calculated using the formula of Cockcroft and Gault (\[140 - Age\] × Mass \[kg\]/\[72 × Creatinine mg/dL\]) (x 0.85 if female).
• •INR or prothrombin time (PT) \< 1.5 × ULN except for participants receiving anticoagulation, who must be on a stable dose of anticoagulant therapy for 6 weeks prior to enrollment
• •No prior treatment for metastatic or unresectable disease except for a maximum of
• •1 dose of chemotherapy with or without nivolumab; prior adjuvant, neo-adjuvant, and peri-operative therapy is allowed, provided it has been completed more than 6 months prior to the first dose of study treatment
• •Fibroblast growth factor receptor 2b (FGFR2b) ≥ 10% 2+/3+ tumor cells (TC) as determined by centrally performed immunohistochemistry (IHC) testing, based on tumor sample either archival (obtained within 6 months/180 days prior to signing pre-screening informed consent) or a fresh biopsy.