A Study of Amivantamab in People With Esophagogastric Cancer

Inclusion Criteria: * Subject or legally authorized representative is willing and able to provide written informed consent. * Patients with previously treated metastatic or unresectable histologically-confirmed esophagogastric cancer who have received at least 1 line of therapy. * EGFR or MET amplification by tissue-NGS with copy number \>8 and/or ctDNA amplification by any FDA and CLIA-approved assay * No prior receipt of an EGFR or MET inhibitor for esophagogastric cancer. (Note: if a patient previously received a EGFR inhibitor, but subsequently demonstrated a MET amplification, or previously received a MET inhibitor, but subsequently demonstrated an EGFR-amplification, inclusion is permitted). * Patients with HER2+ (IHC 3+ or IHC 2+/FISH+) tumors must have progressed on trastuzumab. * Measurable disease based on RECIST 1.1. * ≥ 18 years of age on day of signing informed consent. * Have an ECOG performance status of 0, 1, or 2. * Adequate organ function, defined as: A. Hemoglobin ≥9 g/dL B. ANC ≥1.0 x 10\^9 /L C. Platelets ≥75 x 10\^9 /L D. AST and ALT ≤3 x ULN (≤5 x ULN for subjects with liver metastases) E. Total bilirubin ≤1.5 x ULN; subjects with Gilbert's syndrome can enroll if conjugated bilirubin is within normal limits F. Serum creatinine \<1.5 x ULN or if available, calculated or measured creatinine clearance \>50 mL/min/1.73 m\^2 * Women of childbearing potential and male patients with women of childbearing potential partners must be willing to use an ade…