Gastrointestinal Adenocarcinoma

This study is looking at how safe BHB810 is in adults with gastric and gastroesophageal adenocarcinoma (GEJ). The purpose of this study is also to look at: how well the study drug works, how the study drug moves into, through, and out of the body, and how your body reacts to the study drug. Participants will get an IV infusion of BHB810 every 2 weeks while on study treatment.

The purpose of this study is to find out whether lattice radiation therapy (LRT) is an effective radiation therapy technique when compared to standard stereotactic body radiation therapy (SBRT). The study will also study how the different radiation therapy techniques (LRT and SBRT) affect how many immune cells are able to attack and kill tumor cells (immune infiltration).