ERBB2 and cancer: In particular, weak variants 7–5 and 14–13 are identified as the most promising PNU ADC candidates for treating high Her2 cancers based on the following criteria: 1) they show selective binding to SKOV3 cells and significant (sub nM) ADC potencies and 2) they exhibit the lowest toxicities in low-Her2 cells compared to strong, moderate and WT Herceptin.