Among 36 HER2-positive breast cancer patients eligible for efficacy assessment, the best ORR was 59.1% (13/22) and 71.4% (10/14) at the 4.8 mg/kg and 6.0 mg/kg dose level, respectively; the median PFS was not reached at the time of data cutoff. The gene discussed is ERBB2; the disease is breast cancer.