Synthesis and biological evaluation of seliciclib derivatives as potent and selective CDK9 inhibitors for prostate cancer therapy

Seliciclib is a cyclin-dependent kinase (CDK) inhibitor that has been assayed in phase II clinical trials as an anticancer agent. This paper describes the synthesis of novel derivatives of seliciclib with improved potency, metabolic stability, aqueous solubility, and anti-proliferative activity. The new derivatives showed a novel CDKs selectivity profile. Replacement of ethyl alcohol at position 2 of purine with dimethylaminopropyl and fluorination of benzyl at position 6 of purine of seliciclib resulted in the formation of a derivative that potently and selectively inhibited CDK9 (26 nM vs. CDK9 and > 60-fold selectivity vs. CDK2/5/7). In comparison to seliciclib, this derivative shows lower metabolic clearance (25% lower in Cl_int), higher aqueous solubility and is more cytotoxic in androgen-independent prostate cancer cells. Graphic abstract: