XY028-140 (MS-140) is a potent and selective PROTAC-based CDK4/CDK6 kinase degrader. XY028-140 specifically inhibits RB-E2F signaling and reduces CDK4 and CDK6 protein levels in a dose- and time-dependent manner in vitro. In addition, XY028-140 can degrade its targets by linking them with ubiquitin-proteasome mechanism. Further, the degradation of CDK4/6 protein by XY028-140 is specifically mediated by CRBN. Therefore, XY028-140 effectively and selectively inhibits and degrades CDK4/6 kinase by targeting CDK4/6 kinase in CDK4/6i-S (CDK4/6 inhibitor-sensitive) tumor cells to the CRL4-CRBN-E3 ubiquitin complex. Compared with CDK6 wild-type cells, XY028-140 treatment of cells expressing wild-type or mutation-activated CDK6 resulted in a more effective degradation of CDK6 (S178P).

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Distinct CDK6 complexes determine tumor cell response to CDK4/6 inhibitors and degraders-- Nature Cancer Pub Date : 2021-03-01 , DOI: 10.1038/s43018-021-00174-z