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
1. The subject is able to understand the informed consent form, voluntarily participate and sign the informed consent form.
1. Untreated, or unstable brain parenchymal metastases, spinal cord metastases or compression, cancerous meningitis.