Part 3 evaluated T-DXd plus a fluoropyrimidine and volrustomig, a Programmed cell death protein-1 (PD-1)/cytotoxic T-lymphocyte antigen-4 (CTLA-4) bispecific antibody, in previously untreated HER2+ or HER2-low gastric cancer. The gene discussed is PDCD1; the disease is gastric cancer.