A Randomized, Multicenter, Phase III Open-Label Study of the Efficacy and Safety of Trastuzumab Emtansine Versus Lapatinib Plus Capecitabine in Chinese Patients With HER2-Positive Locally Advanced or Metastatic Breast Cancer Who Have Received Prior Trastuzumab-Based Therapy

This is a Phase III, randomized, multicenter, two-arm, open-label study designed to evaluate
the safety and efficacy of trastuzumab emtansine compared with that of lapatinib +
capecitabine in Chinese participants with HER2-positive, unresectable locally advanced breast
cancer (LABC) or metastatic breast cancer (MBC) who have received prior trastuzumab-based
therapy. A total of approximately 350 participants will be enrolled in China. The study will
consist of 2 stages. Stage 1: Eligible participants will be randomized in a 3:1 ratio to
receive either trastuzumab emtansine or control (lapatinib + capecitabine). Stage 2: After
Stage 1 is recruited, eligible patients will be enrolled to receive trastuzumab emtansine
only.