Development of 9H-purine scaffold as novel CDK2 inhibitors: Design, synthesis, and biological evaluation

Cyclin-dependent kinase 2 (CDK2), a crucial regulator in multiple oncogenic signaling pathways, has emerged as a promising target for the development of innovative anticancer therapies and overcoming resistance to CDK4/6 inhibitors. In this study, three series of compounds were designed and synthesized, using the CDK2 inhibitor fadraciclib (CYC065) as the lead compound, with 9H-purine as the core structure. The design incorporated reported structure-activity relationship data and utilized computer-aided drug design techniques. Compounds in series 1 explored the binding mode between the ATP ribose binding site in CDK2 and C2 substituents, while compounds in series 2 and 3 validated the feasibility of modifying the specific binding region with different substituents and investigated the effects of filling the CDK2 hydrophobic pocket at the N9 position with alkyl substituents. Three compounds, 1f, 2e, and 3a, demonstrated remarkable activity against CDK2-cyclin E2. Notably, 3a exhibited the most potent effect, with a CDK2-cyclin E2 IC₅₀ value of 6.0 ± 0.1 nM, an MV4-11 IC₅₀ value of 489.2 ± 0.2 nM, and excellent selectivity for CDK2. This study evaluated the impact of substitutions at the 2, 6, and 9 positions of the purine ring on the activity of CDK2 small molecule inhibitors. The findings offer a theoretical foundation for future research, broadening the structural diversity and scope of CDK2 inhibitor studies.