ERBB2 and breast carcinoma: PRS-343, the first HER2/4-1BB bispecific antibody to enter human trials, reported a 40% ORR and a 70% DCR (10% CR, 30% PR) in a phase I study (NCT03330561) of 70 patients with HER2+ solid tumor (16 breast cancer), with no serious AEs [184].