JSKN003 Versus Treatment Of Physician'S Choice For HER2-low, Unresectable and/or Metastatic Breast Cancer Subjects

This study is a randomized controlled, open-label, multicenter phase III clinical study evaluating the efficacy and safety of chemotherapy selected by investigator JSKN003 s in subjects with recurrent or metastatic breast cancer who have previously failed first- or second-line chemotherapy in subjects with recurrent or metastatic breast cancer who have failed prior first- or second-line chemotherapy. The study planned to enroll 408 subjects in a 1:1 ratio and stratified block randomization method assigned to: * Experimental group: JSKN003 monotherapy * Control group: investigator's chosen chemotherapy drug (capecitabine, gemcitabine, vinorelbine, docetaxel, albumin-bound paclitaxel, or eribulin) monotherapy.