Therapeutic effect of individual components on (A) HER2-positive BT-474 cells and (B) HER2-negative MDA-MB-231 cells. Cells were treated with (i) trastuzumab-based pretargeting components (Tz-1, Tz20, or Tz29) for 20 min at 37 °C, or (ii) paclitaxel-containing therapeutic components (Px2.2, Px3.3, Alb2.2, or Alb3.3) for 2 h at 37 °C. Cell viability was measured using WST-8 cell viability kit The changes in cell viability were considered significant when p-values were lower than 0.05 (*p < 0.05, **p < 0.01).