A Phase 2 Study to Evaluate the Efficacy, Safety and Pharmacokinetics of YL202 in Patients With BC

Prior treatment

• Have prior treatment with an agent targeting HER3.
• Have prior intolerance to treatment with topoisomerase I inhibitor or an ADC that consists of topoisomerase I inhibitor.
• Have insufficient washout period for prior anticancer therapy prior to first dose of the study drug.
• Have major surgery (excluding diagnostic surgery) within 4 weeks prior to the first dose of study drug or anticipation of major surgery during the study.
• Have prior allogeneic bone marrow transplant or prior solid organ transplant.
• Have received treatment with systemic steroids.
• Have received any live vaccine within 4 weeks prior to the first dose of study drug or intend to receive a live vaccine during the study.
• Have clinically significant concomitant pulmonary diseases.
• Have a history of gastrointestinal perforation and or fistula within 6 months prior to the first dose.
• Have any other primary malignancy within 5 years prior to the first dose of study drug.
• Have unresolved toxicities from prior anticancer therapy.
• Lactating women, or women who are confirmed to be pregnant by pregnancy test within 3 days prior to the first dose.

Other illness

• Have uncontrolled or clinically significant cardiovascular and cerebrovascular disease.
• Have a diagnosis of Gilbert's syndrome.
• Have serious infection.
• Patients with human immunodeficiency virus (HIV) infection.
• Have active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection.
• Have a history of severe hypersensitivity reactions to the drug substance, inactive ingredients in the drug product, or other monoclonal antibodies.

Other

• Have been enrolled in another clinical study concurrently unless it is an observational clinical study or in the follow-up phase of an interventional study.
• Leptomeningeal metastases or carcinomatous meningitis, spinal cord compression.
• Brain metastases with the exceptions.
• Have pleural effusion, abdominal effusion.

• Have been informed of the study before the start of the study and voluntarily sign name and date on the informed consent form.
• Patients with locally advanced or metastatic disease (according to the UICC and AJCC staging system \[Version 8\]) who are not candidates for curative surgery or radiotherapy.
• Patients who are pathologically confirmed advanced/unresectable or metastatic breast cancer with HR-negative and HER2-negative,.
• Patients who are confirmed HR positive and HER2-Zero-expression and HER2-Low-expression.
• Breast cancer patients who have previously failed treatments of HER2-ADC or TROP2-ADC.
• Have at least 1 extracranial measurable lesion as a target lesion per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1
• Have Adequate organ and bone marrow function within 7 days prior to the first dose.
• Female patients of childbearing potential must agree to use highly effective contraception from screening throughout the duration of the study and for at least 6 months after the last dose of study drug.
• Have a expected survival ≥ 3 months.
• Have ability and willingness to comply with protocol-specified visits and procedures.