Abstract: There is provided a compound of formula I and the pharmaceutically acceptable salts and esters thereof wherein X1, X2, R1, R2, R3, R4, R5 and R6 are herein described. The compounds exhibit activity as anticancer agents.

Abstract: Novel 4-aminopyrimidine-5-thione derivatives are disclosed. These compounds inhibit cyclin-dependent kinases, in particular Cdk1, Cdk2 and Cdk4. These compounds and their pharmaceutically acceptable salts 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, colon and prostate tumors.

Abstract: Novel intermediate compounds are disclosed. These compounds are useful in the synthesis of 4-aminopyrimidine-5-one derivatives that inhibit cyclin-dependent kinases, in particular cyclin-dependent kinase 4 (Cdk4). The 4-aminopyrimidine-5-one derivatives and their pharmaceutically acceptable salts have antiproliferative activity and are useful in the treatment or control of cancer, in particular solid tumors.

Abstract: Novel 4-aminothiazole derivatives are disclosed. These compounds inhibit cyclin-dependent kinases. 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, colon and prostate tumors. Also disclosed are intermediates useful in the preparation of these novel 4-aminothiazole derivatives.

Abstract: Novel 2,6-diaminopyridine derivatives of formula wherein R1 and R2 are as defined below, are disclosed. These compounds inhibit cyclin-dependent kinases. 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, colon and prostate tumors. Also disclosed are intermediates useful in the preparation of these novel 2,6-diaminopyridine derivatives.

Abstract: Novel diaminothiazoles of formula (I): are discussed. These compounds selectively inhibit the activity of Cdk4 and are thus useful in the treatment or control of cancer, in particular, the treatment or control of solid tumors. This invention also provides pharmaceutical compositions containing such compounds and methods of treating or controlling cancer, most particularly, the treatment or control of breast, lung, colon, and prostate tumors.