JSKN016 in Combination With D-0502 for Locally Advanced or Metastatic HR-Positive, HER2-Negative Breast Cancer

Inclusion Criteria: * Age ≥18 years * Histologically or cytologically confirmed locally advanced or metastatic HR-positive, HER2-negative breast cancer * HR-positive defined as ER and/or PR ≥1% by IHC * HER2-negative per ASCO/CAP guidelines * At least one measurable extracranial lesion per RECIST v1.1 * ECOG performance status 0-1 * Prior progression on CDK4/6 inhibitor plus endocrine therapy * Adequate organ and cardiac function * Postmenopausal women, or premenopausal women receiving ovarian function suppression Exclusion Criteria: * Active or untreated CNS metastases * Prior treatment with ADCs containing topoisomerase I inhibitor payloads * Active interstitial lung disease or pneumonitis * Uncontrolled cardiovascular disease or active infection * Prior malignancy within 5 years (with specific exceptions) * Pregnancy or breastfeeding