One approach used the SpyTag/SpyCatcher (ST/SC) system to modify P22 VLP wiffleball (WB) particles with either an epidermal growth factor receptor affibody (EGFRaf) or a human epidermal growth factor receptor2 affibody (HER2af) to target breast cancer cells and deliver the prodrug Aldoxorubicin (AlDox) (Figure 7A) [12]. The gene discussed is EGFR; the disease is breast carcinoma.