Discovery of Potent and Exquisitely Selective Inhibitors of Kinase CK1 with Tunable Isoform Selectivity

Abstract

Casein kinases 1 (CK1) are key signaling molecules that have emerged recently as attractive therapeutic targets in particular for the treatment of hematological malignancies. Herein, we report the identification of a new class of potent and highly selective inhibitors of CK1α, δ and ϵ. Based on their optimal in vitro and in vivo profiles and their exclusive selectivity, MU1250, MU1500 and MU1742 were selected as quality chemical probes for those CK1 isoforms. At proper concentrations, MU1250 and MU1500 allow for specific targeting of CK1δ or dual inhibition of CK1δ/ϵ in cells. The compound MU1742 also efficiently inhibits CK1α and, to our knowledge, represents the first potent and highly selective inhibitor of this enzyme. In addition, we demonstrate that the central 1H‐pyrrolo[2,3‐b]pyridine‐imidazole pharmacophore can be used as the basis of highly selective inhibitors of other therapeutically relevant protein kinases, e.g. p38α, as exemplified by the compound MU1299.

Splice variants of CK1α and CK1α-like: Comparative analysis of subcellular localization, kinase activity, and function in the Wnt signaling pathway

“…In contrast, the tested inhibitors target CK1α-like with much lower affinity. We conclude that (i) the established NanoBRET assay was functional and constant with other cellular assays reporting inhibition of CK1α ( 50 ) and (ii) individual CK1α variants are targeted with equal potency suggesting that ATP-competitive CK1α inhibitors target all CK1α splice variants but not CK1α-like in vivo .…”

“…BTX-A51 is the first inhibitor targeting CK1α to enter clinical trials (NCT04243785) for the treatment of acute myeloid leukemia and myelodysplastic syndrome ( 11 , 17 , 18 ). MU1742 is a recently developed small molecule inhibitor of CK1α with kinome-wide selectivity superior to that of BTX-A51 ( 50 ).…”

“…The compounds tested were MU1742, BTX-A51, and D4476. D4476 is an inhibitor of CK1δ and ALK5 ( 47 ); however, it has been shown to block CK1α at high concentrations ( 48 , 49 , 50 ). It has been used in the past for the description of the CK1α biology, mainly due to the lack of more CK1α-specific inhibitors at that time.…”

“…Interestingly, this was not the case for CK1α-like that was inhibited significantly less efficiently. Our NanoBRET assay represents an optimized version of CK1α NanoBRET published earlier ( 50 ), yielding results well in line with other functional cellular assays ( 50 ). We conclude that MU1742, given its excellent kinome-wide selectivity and high potency towards all tested CK1α variants in cellular environment, represents currently the best chemical probe to study CK1α biology.…”