Esophageal Cancer Clinical Trials

• Age 18 years or older at time of signing informed consent.

• ECOG performance status 0-1.

• HER2+ esophageal, GEJ, or gastric adenocarcinoma biopsy or resection specimen as defined by local HER2 IHC3+ or IHC 2+/FISH\>2.0 expression.

• Complete surgical resection of the primary tumor must be achievable

• Demonstrate adequate organ function as defined in Table 1.

∙ Table 1 - Organ Function Requirements for Eligibility Hematological

• Absolute neutrophil count (ANC): ≥1,500 /mcL

• Platelets: ≥100,000 / mcL

• Hemoglobin: ≥8 g/dL Renal

• Creatinine clearance: ≥ 50 mL/minute Hepatic

• Serum total bilirubin: ≤ 1.5 X ULN OR Direct bilirubin ≤ ULN for subjects with total bilirubin levels \> 1.5 ULN. Except patients with Gilbert's disease (≤3x ULN)

• AST and ALT: ≤ 2.5 X ULN

• Albumin: \>3 mg/dL Coagulation

• International normalized ratio (INR) OR prothrombin time (PT) Activated partial thromboplastin time (aPTT): \<1.5 x ULN unless participant is receiving anticoagulant therapy as long as PT or aPTT is within therapeutic range of intended use of anticoagulants

• Male participants: A male participant must agree to use contraception as detailed in Section 15.3 of this protocol during the treatment period and for at least 230 days (5 terminal half-lives of trastuzumab \[140\] plus an additional 90 days \[spermatogenesis cycle\]) after the last dose of study treatment and refrain from donating sperm during this period.

• Female participants: A female participant is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies:

‣ Not a woman of childbearing potential (WOCBP) as defined in section 15.3 OR

⁃ A WOCBP who agrees to follow the contraceptive guidance in section 15.3 during the treatment period and for at least 170 days (140 days plus an additional 30 days \[menstruation cycle\]) after the last dose of study treatment.