ERBB2 and gastric cancer: We found that 1) RC48-ADC exceeded trastuzumab in GC PDX models with HER2 expression, even in models with moderate to low expression of HER2; 2) RC48-ADC exerted an antitumor effect by inhibiting the phosphorylation of HER2, inducing G2/M phase arrest and cell apoptosis in HER2-expressed PDX models; 3) RC48-ADC had satisfactory efficacy in HER2-positive and HER2-moderate expressed GC patients and demonstrated promising efficacy in HER2-positive patients who have progressed after anti-HER2 therapy.