The trial comprises Phase I dose escalation/expansion and Phase II combination therapy. Using a multicenter, open-label, non-randomized design, breast cancer patients will receive TQB3126 to assess its safety, tolerability, pharmacokinetics and preliminary efficacy.
Subjects voluntarily participate in this study, sign the informed consent form, and demonstrate good treatment compliance.
Aged 18 to 75 years at the time of informed consent signature; Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of 0 or 1; estimated survival expectancy of more than 3 months.
Histopathologically confirmed breast cancer.
Documented disease progression confirmed by clinical or imaging evidence during or after the most recent prior systemic therapy prior to the first study drug administration.
Other malignant tumors within 5 years prior to first dose, except those cured by single surgical treatment with at least 5 years of disease-free survival, or cured differentiated thyroid cancer, cervical carcinoma in situ, non-melanoma skin cancer, or superficial bladder tumors.
Conditions affecting intravenous access or blood sampling, or multiple factors affecting oral drug administration/absorption (e.g., inability to swallow, chronic diarrhea, intestinal obstruction).
Unresolved toxicity from prior therapy of Grade >1 (CTCAE v6.0), except Grade 2 alopecia, Grade 2 anemia, clinically insignificant laboratory abnormalities, or hypothyroidism stable on hormone replacement therapy.
Major surgery, significant traumatic injury within 4 weeks before first dose, anticipated need for major surgery during the study, or long-standing unhealed fracture.