A Phase II Clinical Study of SSGJ-612 in Combination With a Human Epidermal Growth Factor Receptor 2 (HER2)-Targeted Antibody-Drug Conjugate (ADC) in Patients With Hormone Receptor (HR)-Positive, HER2-Low or HER2-Ultralow Expression Metastatic Breast Cancer
This study is a phase II clinical trial of SSGJ-612 combined with a human epidermal growth factor receptor 2 (HER2)-targeted antibody-drug conjugate (ADC) in patients with hormone receptor (HR)-positive, HER2-low or HER2-ultralow metastatic breast cancer.
• Voluntary participation in this study, signed informed consent form, good treatment compliance, and willingness to cooperate to complete all trial procedures.
• Expected survival duration ≥ 3 months.
• Histopathologically confirmed breast cancer meeting all of the following criteria simultaneously:
‣ Metastatic tumor;
⁃ Tumor samples tested by central laboratory confirmed as HER2-low or HER2 ultra-low expression;
⁃ No prior test results reporting HER2 positivity;
⁃ Tumor sample testing confirms hormone receptor-positive (HR+) status.
• Patients must satisfy either of the following conditions:
‣ Disease progression within 6 months after initiation of first-line endocrine therapy combined with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors for metastatic disease;
⁃ Received at least 2 lines of prior endocrine therapy for metastatic disease, with disease progression post-treatment.
• Participants in Part 1: Breast cancer patients who have received at least one line of chemotherapy for metastatic disease; Participants in Part 2: Breast cancer patients who have not received any chemotherapy for metastatic disease.
• At least one repeatedly and accurately measurable tumor lesion as target lesion assessed per RECIST v1.1 criteria.