– G-573 is an allosteric inhibitor of MEK that is both potent and selective. The IC(50) value for pERK inhibition in HCT116 tumours by G-573 was estimated to be 0.406  µM. The IC(50) values for tumour growth inhibition in HCT116 and H2122 were estimated to be 3.43 and 2.56 µM, respectively. ED(50) estimates in HCT116 and H2122 mouse xenograft models were estimated to be ~4.6 and 1.9 mg/kg/day, respectively.