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

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