SR-1277 is a highly potent, selective, and ATP competitive inhibitor of CK1delta/epsilon, with IC50 values of 49 nM and 260 nM, respectively. Additionally, SR-1277 exhibits inhibitory effects on FLT3, CDK4/cyclin D1, CDK6/cyclin D3, and CDK9/cyclin K, with IC50 values of 305 nM, 1340 nM, 311 nM, and 109 nM, respectively. Taken together, SR-1277 represents a valuable tool for cancer research.