CK1-IN-2 (compound Nr.4) is a potent CK1 inhibitor with IC50 values of 123, 19.8, 26.8, and 74.3 nM for CK1a, CK1d, CK1e, and p38a, respectively, and is used in DUX4 overexpression-associated diseases, such as muscular dystrophy.

CK1a:19.8 nM, CKIα:123 nM, CK1d:26.8 nM, CK1e:74.3 nM

CK1-IN-2 (compound No. 4) is a potent inhibitor of casein kinase 1 (CK1), with IC₅₀ values of 123 nM (CK1α), 19.8 nM (CK1a), 26.8 nM (CK1d), and 74.3 nM (CK1e), indicating subtype selectivity[1]. CK1-IN-2 (0.02-10 μM, 72 h) promotes myotube formation in FSHD (facioscapulohumeral muscular dystrophy) cells, indicating its role in enhancing muscle cell fusion[1]. At 10 μM (72 h), CK1-IN-2 is also capable of reversing the inhibitory effect of Losmapimod on myotube formation[1].