ERBB2 and breast cancer: Fig 5A described the dose-dependent anti-breast cancer toxicity using free drugs. It is shown that the viability of HER2+ BT474 cells was reduced by MMAE to 12% at concentration of 12 nM and 6% at 60 nM, and the viability was decreased by DM1 to 62% at 12 nM and 11% at 60 nM.