XMU-MP-1 is an inhibitor of the pro-apoptotic, sterile 20-like kinases MST1 and 2 (IC50s = 71.1 and 38.1 nM, respectively). It is selective for MST1 and 2 over a panel of 468 kinases at a concentration of 1 μM. XMU-MP-1 inhibits phosphorylation of MOB1, LATS1 and 2, and YAP in HepG2 cells as well as MST1 and 2 autophosphorylation in RAW 264.7, U2OS, SW480, RPE1, SNU423, and HepG2 cells in a concentration-dependent manner. It also prevents cell death induced by overexpression of MST2. XMU-MP-1 (1 mg/kg) enhances liver regeneration in mice post partial hepatectomy and reduces liver fibrosis in a mouse model of chronic liver injury.