This is a phase III, multicenter, open-label, randomized controlled study comparing GQ1005 with Trastuzumab Emtansine (T-DM1) in patients with HER2-positive unresectable or metastatic breast cancer previously treated with trastuzumab and taxane. Approximately 228 patients with unresectable or metastatic HER2-positive breast cancer will be randomized 1:1 to receive GQ1005 or T-DM1, respectively.
