MR24 TFA, a G-5555 derivative, is a mammalian STE20-like (MST) kinase inhibitor. MR24 TFA shows selectively to MST3/4 over MST1/2, with EC50 values of 57 and 583 nM, respectively. MR24 TFA induces G1 phase cell cycle arrest. MR24 TFA can be used for cancer research, such as breast, liver and lung cancers[1].