Among bispecific antibodies, zenocutuzumab is an anti-HER2 and HER3 IgG1 more potent than pertuzumab in inhibiting HER2-HER3 heterodimerization which was initially tested in hormone receptor (HR)+/HER2-low breast cancer xenograft models, suggesting a potential synergistic effect with endocrine therapy (Geuijen et al., 2018; Antonarelli et al., 2021b). This evidence concerns the gene ERBB2 and breast cancer.