Inclusion Criteria:

• Adults with unresectable, locally advanced or metastatic gastric or gastroesophageal junction cancer not amenable to curative therapy.
• Confirmed fibroblast growth factor receptor 2b (FGFR2b) overexpression by immunohistochemistry (IHC) (central testing result).
• Eastern Cooperative Oncology Group (ECOG) less than or equal to 1.
• Measurable, evaluable, or non-evaluable disease as long as evaluable by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.
• Participant has no contraindications to mFOLFOX6 chemotherapy.
• Adequate organ and bone marrow function:
  • absolute neutrophil count greater than or equal to 1.5 times 10^9/L;
  • platelet count greater than or equal to 100 times 10^9/L;
  • hemoglobin greater than or equal to 9 g/dl;
  • aspartate aminotransferase (AST) and alanine aminotransferase (ALT) less than 3 times the upper limit of normal (ULN) (or less than 5 times ULN if liver involvement).
  • total bilirubin less than 1.5 times ULN (or less than 2 times ULN if liver involvement); with the exception of participants with Gilbert's disease);
  • calculated or measured creatinine clearance (CrCl) of greater than or equal to 30 mL/minute calculated using the formula of Cockcroft and Gault -international normalized ratio (INR) or prothrombin time (PT) less than 1.5 times ULN except for participants receiving anticoagulation, who must be on a stable dose of anticoagulant therapy for 6 weeks prior to enrollment.

Exclusion Criteria:

• Prior treatment for metastatic or unresectable disease.
  • Note: prior adjuvant or neo-adjuvant therapy for local disease is allowed if ended more than 6 months of 1st dose.
• Prior treatment with any selective inhibitor of fibroblast growth factor.
• ibroblast growth factor receptor (FGF-FGFR) pathway.
• Known human epidermal growth factor receptor 2 (HER2) positive.
• Untreated or symptomatic central nervous system (CNS) disease or brain metastases.
• Peripheral sensory neuropathy greater than or equal to Grade 2.
• Clinically significant cardiac disease.
• Other malignancy within the last 2 years (exceptions for definitively treated disease).
• Chronic or systemic ophthalmological disorders.
• Major surgery or other investigational study within 28 days prior to first dose of study treatment.
• Palliative radiotherapy within 14 days prior to the first dose of study treatment.
• Abnormalities of the cornea that may pose an increased risk of developing a corneal ulcer.

Eligibility last updated 10/22/21. Questions regarding updates should be directed to the study team contact.