ERBB2 and breast cancer: Each delivery component is functionalized with bioorthogonal reactive groups that quickly react <i>in situ</i>, forming cross-linked clusters on the cell surface, which facilitates rapid internalization and intracellular delivery of therapeutics.<h4>Procedures</h4>We have successfully developed a click chemistry-based pretargeting platform for HER2(+) BC enabling PET-MR image guidance for reduced radiation dose, high sensitivity, and good soft tissue contrast.