CD44 and breast cancer: Wu et al. obtained CD44-specific ligands using hyaluronic acid (HA), developed in 2020, to encapsulate doxorubicin (Dox) combined with azithromycin, DSPE-PEG2000-HA and in vitro experiments demonstrated that HA-Exo-Dox selectively bound to CD44-overexpressing cancer cells, specifically to breast cancer cells and lung cancer cells.