IC261

IC261 is a reversible, ATP-competitive inhibitor of casein kinase 1 (CK1) (IC₅₀ = ~1 µM for CK1δ and CK1ɛ and 16 µM for CK1α). It is at least 100-fold less effective against PKA, p34cdc2, and p55fyn. IC261, at 1 µM, inhibits cytokinesis in primary mouse embryo fibroblasts. IC261 induces cell cycle arrest and apoptosis of human cancer cells via CK1δ/ɛ and Wnt/β-catenin independent inhibition of mitotic spindle formation.