Synthesis of a new series of pyrazolo [1,5-a]pyrimidines as CDK2 inhibitors and anti-leukemia

Based on the structural study of previously known CDK2 inhibitors, a new series of pyrazolo [1,5-a]pyrimidine derivatives was designed and synthesized. The target compounds were biologically assessed as potent CDK2 inhibitors and promising anti-leukemia hits. The 7-(4-Bromo-phenyl)-3-(3-chlom/2-chloro-phenylazo)-pyrazolo[1,5-a]pyrimidin-2-ylamines 5 h and 5i revealed the best CDK2 inhibitory activity with comparable potency (IC50 = 22 and 24 nM, respectively) to that of dinaciclib (IC50 = 18 nM). Additionally, both analogues showed potent activities against CDK1, CDK5 and CDK9 at nanomolar concentrations (IC50 = 28-80 nM). The antileukemia screening of the target compounds showed strong to moderate cytotoxicity against the used leukemia cell lines (MOLT-4 and HL-60). Compound 5 h inhibited MOLT-4 and HL-60 by 1.4 and 2.3 folds (IC50 = 0.93 and 0.80 mu M), respectively, compared to dinaciclib (IC50 = 1.30 and 1.84 mu M). Furthermore, compound 5i was comparable to dinaciclib against MOLT-4 and exhibited twice its activity against HL-60. Besides, the cytotoxicity of the promising analogues on normal human blood cells indicated the safety of 5h and 5i as compared to the reference dinaciclib. The pharmacokinetic properties of 5h and 5i were predicted using ADME calculations revealing good oral bioavailability and high GI absorption. The molecular docking simulations indicated, as expected, that the dinaciclib analogues can well-accommodate the CDK2 binding site, forming a variety of interactions.

Automated summary

A new series of pyrazolo [1,5-a]pyrimidine derivatives were synthesized based on known CDK2 inhibitors, showing potent CDK2 inhibition and promising anti-leukemia activity. The compounds exhibited comparable inhibitory potency to dinaciclib against CDK2, as well as strong activities against CDK1, CDK5, and CDK9 at nanomolar concentrations. Additionally, the compounds showed strong to moderate cytotoxicity against MOLT-4 and HL-60 leukemia cell lines, with some analogues demonstrating higher activity than dinaciclib. Pharmacokinetic predictions indicated good oral bioavailability and high GI absorption for the compounds. Molecular docking simulations suggested that the analogues can effectively bind to the CDK2 binding site.