A Study Comparing BL-B01D1 With Chemotherapy of Physician's Choice in Patients With Unresectable Locally Advanced, Recurrent, or Metastatic HR+/HER2- Breast Cancer After Failure of Prior Endocrine Therapy(PANKU-Breast03)

In this trial, the experimental group receives BL-B01D1, and the control group receives chemotherapy of physician's choice.

Inclusion criteria

• Voluntarily sign the informed consent form and comply with the protocol requirements;
• No gender restrictions;
• Age ≥ 18 years;
• Expected survival time ≥ 3 months;
• Patients with unresectable locally advanced, recurrent, or metastatic HR+ HER2- breast cancer;
• Trial participants have not received systemic chemotherapy;
• Trial participants have progressed after at least one line of endocrine therapy, etc.;
• Documented radiographic disease progression prior to enrollment;
• Agree to provide archived tumor tissue specimens or fresh tissue samples from the primary or metastatic lesion within 3 years;
• Must have at least one measurable lesion as defined by RECIST v1.1;
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1;
• Toxicity from prior anti-tumor therapy must have recovered to ≤ Grade 1 as defined by NCI-CTCAE v6.0;
• No severe cardiac dysfunction, with left ventricular ejection fraction (LVEF) ≥ 50%;
• Must meet required organ function levels;
• Urinary protein ≤ 2+ or < 1000 mg/24h;
• For premenopausal women of childbearing potential, a pregnancy test must be performed within 7 days before starting treatment, with a negative serum pregnancy result, and they must not be breastfeeding; all enrolled patients (regardless of gender) must use adequate barrier contraception throughout the treatment period and for 6 months after treatment ends.

Exclusion criteria

• Previously treated with ADC drugs that use topoisomerase I inhibitors as the toxin or target EGFR and/or HER3;
• Use of chemotherapy, biotherapy, immunotherapy, etc., within 4 weeks or 5 half-lives before the first dose;
• Previous treatment with anthracycline drugs where the equivalent cumulative dose of doxorubicin exceeds 360 mg/m²;
• History of severe cardiovascular or cerebrovascular diseases;
• Unstable thrombotic events requiring therapeutic intervention within 6 months before screening;
• Prolonged QT interval, complete left bundle branch block, etc.;
• Diagnosis of another malignancy within 3 years before the first dose;
• Hypertension poorly controlled by two antihypertensive medications;
• Poorly controlled blood glucose levels;
• History of ILD requiring steroid therapy, current ILD, or grade ≥2 radiation pneumonitis, etc.;
• Concurrent pulmonary diseases causing clinically severe respiratory function impairment;
• Patients with active central nervous system metastases;
• Presence of large serous cavity effusions or symptomatic serous cavity effusions, etc.;
• Imaging findings indicating tumor invasion or encasement of the abdomen, chest, etc.;
• Severe infection within 4 weeks before study randomization;
• Severe, unhealed wounds, ulcers, or fractures within 4 weeks before signing the informed consent form;
• Trial participants with clinically significant bleeding or a significant bleeding tendency within 4 weeks prior to signing the informed consent form;
• History of inflammatory bowel disease, extensive bowel resection, etc.;
• Patients with a history of allergy to recombinant humanized antibodies or allergy to BL-B01D1 or any of its excipients;
• History of autologous or allogeneic stem cell transplantation;
• Positive for human immunodeficiency virus antibodies, active hepatitis B virus infection, or hepatitis C virus infection;
• Receipt of other unapproved clinical study drugs or treatments within 4 weeks before the first dose;
• Trial participants planning to receive or having received live vaccines within 28 days before the first dose;
• Other conditions deemed by the investigator to be unsuitable for participation in this clinical trial due to complications or other reasons.