A phase II study (NCT05190445) is ongoing to investigate the efficacy of PRS-343 in combination with ramucirumab and paclitaxel in patients who have already received treatment for HER2-high (IHC 3+ or IHC 2+ with HER2/neu gene amplification) G/GEJ adenocarcinoma and in combination with tucatinib in HER2-low (IHC 1+ or IHC 2+ without HER2/neu gene amplification) G/GEJ adenocarcinoma. This evidence concerns the gene ERBB2 and gastroesophageal junction adenocarcinoma.