A Study to Evaluate the Pharmacokinetics of Margetuximab in Chinese Patients With HER2+ MBC

Approximately 16\~20 Chinese subjects will be enrolled. Eligible subjects are HER2 positive, metastatic breast cancer who has received standard anti-HER2 directed therapy in the metastatic setting in Chinese patients. Subjects should have received treatment with at least one, and no more than four lines of therapy overall in the metastatic setting. Eligible subjects will receive margetuximab plus chemotherapy. The dosage and administering of margetuximab is 15 mg/kg IV Q3W. Investigators selected one of three backbone chemotherapy regimens given at standard doses: capecitabine, vinorelbine or gemcitabine. Subject will receive the treatment until disease progression, unacceptable toxicity, withdrawal of consent, initiation of subsequent anti-tumor treatment therapy, or death (whichever occurs first).