Pertuzumab Sensitively Detects Trastuzumab- Mediated HER2 Downregulation and Tumor Response in Athymic Mice Bearing MDA- MB-361 Human Breast Cancer Xenografts

In-DTPA-pertuzumab)couldsensitivelydetect an early molecular response to trastuzumab manifested byHER2downregulationandalatertumorresponserevealedbyade-creased number of HER2-positive viable tumor cells. Methods:Changesin HER2densityinSKBr-3andMDA-MB-361BCcellsex-posed to trastuzumab (14 mg/mL) in vitro were measured by satu-ration binding assays using