Progress toward the development of agents to modulate the cell cycle.

With taxanes continuing to prove useful in the clinical treatment of cancer, the next generation of antimitotic agents has entered clinical trials. Other mechanisms awaiting proof-of-concept for the treatment of antiproliferative diseases include inhibition of cyclin-dependent kinases (Cdks). Flavopiridol and UCN-01 are continuing in clinical trials, and newer more selective Cdk inhibitors are now entering clinical evaluation.