Phase 1b/2 Study of U3-1287 in Combination With Trastuzumab Plus Paclitaxel in Newly Diagnosed Metastatic Breast Cancer (MBC)

U3-1287: 18 mg/kg administered intravenously once every three weeks

Trastuzumab: 6 mg/kg up to 8 mg/kg administered intravenously once every three weeks

Paclitaxel: 175 mg/m\^2 administered intravenously once every three weeks

The maximum tolerated dose as determined in Phase 1b portion (between 9 mg/kg and 18 mg/kg) administered intravenously once every three weeks

Trastuzumab: 6 mg/kg up to 8 mg/kg administered intravenously once every three weeks

Paclitaxel: 175 mg/m\^2 administered intravenously once every three weeks

Placebo: Dose corresponding to U3-1287 administered intravenously once every three weeks