Src Inhibitor4 (Compound 18) is a derivative of KX-01 and functions as a Src inhibitor. It effectively disrupts tumor cells, damages microtubules, and induces cell cycle arrest, apoptosis, and immunogenic cell death. After introducing phenol or aniline functional groups, Src Inhibitor4 serves as a payload conjugation site for antibody-drug conjugates, showcasing antitumor activity.