Study of KN026 Monotherapy or Combination Therapy in Patients With Metastatic Breast Cancer

Phase II Study of Efficacy and Safety Evaluation of KN026 Monotherapy or Combination Therapy in Patients With HER2 Expressing or Positive Metastatic Breast Cancer

This is an open-label, three-cohort phase 2 study of KN026 in subjects with advanced breast Cancer.

KN026 is an anti-HER2 bispecific antibody that can simultaneously bind two non-overlapping epitopes of HER2, leading to a dual HER2 signal blockade.The HER2- positive mBC subjects without systemic treatment will be enrolled in cohort 1 and received 30 mg/kg KN026 and docetaxol. The HER2 low expression and hormone-receptor positive mBC subjects failed standard chemotherapy and hormone therapy will be enrolled in cohort 2 and received 30 mg/kg KN026 monotherapy. The HER2 low expression and hormone-receptor negative/weak positive mBC subjects failed standard chemotherapy will be enrolled in cohort 3 and received 30 mg/kg KN026 and 5 mg/kg KN046

Inclusion Criteria:

• Male or female subject >= 18 years
• Histologically/cytologically confirmed, locally advanced unresectable or metastatic breast cancer
• ECOG score 0 or 1
• Life expectancy >3 months
• According to the definition of RECIST1.1, the patient has at least one measurable lesion
• Adequate organ function prior to start treatment with KN026
• Able to understand, voluntarily participate and willing to sign the ICF

Exclusion Criteria:

• Accepted any other anti-tumor drug therapies within 4 weeks before fist dose
• Accepted radiotherapy within 4 weeks before enrollment
• Subjects are eligible with clinically controlled and stable neurologic function >= 4 weeks, which is no evidence of CNS disease progression; Subjects with spinal cord compression and cancerous meningitis are not eligible
• Pregnant or nursing females；or intend pregnancy within this study period or within 6 monthes after the end of this study
• History of immunodeficiency, including HIV positive or other acquired, congenital immunodeficiency disease, or a history of organ transplantation
• History of immunodeficiency, including HIV positive or other acquired, congenital immunodeficiency disease, or a history of organ transplantation
• Cavity effusion (pleural effusion, ascites, pericardial effusion, etc.) are not well controlled, and need locally treatment or repeated drainage