KN035 in Combination With Trastuzumab and Docetaxel in HER2-positive Breast Cancer

Inclusion Criteria: * Written informed consent * Female subjects with age 18 to 70 (inclusive) years at the time of consent * LVEF ≥50% at baseline * ECOG performance status of 0-1 * Have not received 1L treatment for recurrent or metastatic breast cancer * Adequate organ function Exclusion Criteria: * History of exposure to the cumulative doses of doxorubicin \> 400 mg / m2 or equivalent * History of autoimmune diseases * Active brain metastasis * Concurrent diseases that compromise patient's safety