CYNK-101 in Combination with Trastuzumab and Pembrolizumab in Patients with Locally Advanced Unresectable or Metastatic HER2-Positive Gastric or Gastroesophageal Junction (G/GEJ) Adenocarcinoma

This study will find the maximum tolerated dose (MTD) of CYNK-101 which contains Natural Killer (NK) cells derived from human placental CD34+ cells and culture-expanded. CYNK-101 will be administered as first-line treatment, following induction therapy consisting of Pembrolizumab, Trastuzumab and a Fluoropyrimidine / Platinum based Chemotherapy regimen. Patients are required to undergo a biopsy for confirmation of HER2 positivity defined as either IHC 3+ or IHC 2+ with a positive fluorescent in-situ hybridization (FISH) or FISH + alone. The safety of this treatment will be evaluated, and researchers will want to learn if NK cells will help in treating patients with Locally Advanced Unresectable or Metastatic HER2-Positive Gastric or Gastroesophageal Junction (G/GEJ) Adenocarcinoma.