PDCD1 and gastroesophageal junction adenocarcinoma: RC48 is a novel humanized anti-HER2 antibody conjugated to monomethyl auristatin E. RC48 was tested together with toripalimab, an anti-PD1 antibody, in patients with advanced GC or GEJ adenocarcinoma and positive HER2 expression that were refractory to at least one line of treatment.121 In patients with GC or GEJ adenocarcinoma, the confirmed objective response rate was 43%.