Trastuzumab is a humanized monoclonal antibody for patients with invasive breast cancers that overexpress HER2. Trastuzumab has been clinically used to treat HER2 Positive Metastatic Breast Cancer and HER2 Positive Gastric Cancer.

METHODS: Human breast cancer cells BT-474 were treated with Trastuzumab (0.01-10 µg/mL) for 72 h. Cell viability was determined by MTS Assay.
RESULTS: The antiproliferative effect of Trastuzumab was observed at concentrations as low as 0.5 µg/mL, with a stabilizing level of approximately 10 µg/mL.[1]
METHODS: CHO-K6, CHO-EGFR and CHO-HER3 cells were treated with Trastuzumab (0.1-10 µg/mL) for 5-60 min, and binding to HER receptors was detected by Immunofluorescence.
RESULTS: Trastuzumab binds only to HER2, but not to EGFR and HER3. [2]

METHODS: To test the in vivo antitumor activity, Trastuzumab (5 µg/g) was administered intraperitoneally once a week for seven doses to nude mice harboring human mammary carcinoma tumor JIMT-1.
RESULTS: Trastuzumab had a significant inhibitory effect on tumor growth on days 21-56. After stopping administration, tumors began to grow in two nude mice whose tumors were palpable earlier. [3]