RecruitingPhase 2Drug trialNeratinib In Combination With Chemotherapy/Trastuzumab/Pembrolizumab In HER2 Gastroesophageal CancerThe purpose of the study is to test the effects, both good and bad, of the research study drug Neratinib in combination with Trastuzumab, Pembrolizumab and FOLFOX chemotherapy. This study will also look at the safety of Neratinib in combination with Trastuzumab, Pembrolizumab and FOLFOX in HER2 overexpressing Gastroesophageal cancers.