The present invention relates to compounds of Formula (I) that function as inhibitors of MerTK activity, to processes for the preparation of such compounds, to pharmaceutical compositions comprising them and to their use in the treatment of proliferative disorders, such as cancer, as well as other diseases or conditions in which (MerTK) activity is implicated: (I) Formula (I) wherein R1, X1, Ring A, Ring B and Ring C are each as defined herein.