Definition

The isethionate salt form of dalpiciclib, an orally bioavailable cyclin-dependent kinase (CDK) inhibitor, with potential antineoplastic activity. Upon oral administration, dalpiciclib selectively inhibits cyclin-dependent kinase 4 (CDK4) and 6 (CDK6). This inhibits retinoblastoma (Rb) protein phosphorylation early in the G1 phase, which prevents CDK-mediated G1-S phase transition and leads to cell cycle arrest. This suppresses DNA replication and decreases tumor cell proliferation. CDK4 and 6 are serine/threonine kinases that are upregulated in many tumor cell types and play a key role in the regulation of cell cycle progression.