The study is being conducted to explore the reasonable dosage and evaluate the efficacy, safety and tolerability of HLX43 (Anti-PD-L1 ADC) as a monotherapy or in combination with immune checkpoint inhibitors in Subjects with locally advanced, recurrent or metastatic triple-negative breast cancer (TNBC).
Voluntary written informed consent obtained before any study procedures.
Age ≥ 18 years at consent; no gender restriction.
Histopathologically confirmed TNBC: ER < 1%, PR < 1%, HER2 IHC 0/1+/2+ with no FISH amplification.
Phase I: Recurrent or metastatic TNBC after ≥1 prior line of standard systemic therapy.
Prior topoisomerase I-targeting therapy (e.g., irinotecan, topotecan, or ADCs).
Second primary malignancy within 2 years before randomization (except cured carcinoma in situ or stage I tumors).
Prior grade ≥3 immune-related adverse event during immunotherapy.
Uncontrolled, recurrent malignant pleural, pericardial, or ascitic effusions requiring repeated drainage.
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Treatment groupsSee each treatment group below.