The goal of this clinical trial is to assess the efficacy of DB-1303/BNT323 compared with investigator's choice chemotherapy in terms of progression-free survival (PFS) by blinded independent central review (BICR) in the HR+, HER2-low (immunohistochemistry [IHC]2+/in situ hybridization [ISH]- and IHC 1+) population.
