ZK53 is a selective activator of mitochondrial caseinolytic protease P (HsClpP) (EC₅₀: 1.37?μM for α-casein hydrolysis by HsClpP). ZK53 is is inactive toward bacterial ClpP proteins. ZK53 induces apoptosis in H1703, H520 and SK-MES-1 cells. ZK53 induces dysregulation of mitochondrial functions in lung squamous cell carcinoma (LUSC) cells. ZK53 inhibits tumor growth in H1703 xenograft mouse model^[1].