Flavopiridol, the first cyclin-dependent kinase inhibitor: recent advances in combination chemotherapy.

The cell cycle is the series of events necessary for the division and duplication of a cell. The dysregulation of the cell cycle can promote the development of cancer. A group of proteins, cyclin-dependent kinases (CDKs), that control the cell cycle, provide new targets for treating cancer. As a result, cyclin-dependent kinase inhibitors (CDKIs) represent a novel class of chemotherapeutic agents. Of these, flavopiridol, a semisynthetic flavonoidal alkaloid, emerged as the first CDKI to enter clinical trials. Preclinical data indicate that flavopiridol could block the proliferation of neoplastic cells and induce programmed cell death as a single agent. Furthermore, recent emerging data revealed that flavopiridol can potentiate, generally in a dose- and sequence-dependent manner, the anti-tumor effects of many established chemotherapeutic agents. This review is primarily focused on the role of flavopiridol in combination with various therapeutic agents that are in or near clinical development.