Disclosed are novel naphthostyrils of formula These compounds inhibit cyclin-dependent kinases (CDKs), in particular CDK2. These compounds and their pharmaceutically acceptable salts and esters are anti-proliferative agents useful in the treatment or control of cell proliferative disorders, in particular cancer. Also disclosed are pharmaceutical compositions containing such compounds, methods for the treatment and/or prevention of cancer using such compositions, and intermediates useful in the preparation of the compounds of formula I.