Abstract: The present invention is directed to novel diaminothiazoles of formula These compounds inhibit cyclin-dependent kinase 4 (Cdk4) and are selective against Cdk2 and Cdk1. These compounds and their pharmaceutically acceptable salts and esters have antiproliferative activity and are useful in the treatment or control of cancer, in particular solid tumors. This invention is also directed to pharmaceutical compositions containing such compounds and to methods of treating or controlling cancer, most particularly the treatment or control of breast, lung and colon and prostate tumors.