Flavopiridol is obtained from a synthetic process, but its chemical structure is identical to a product obtained from an indigenous plant in India called Dysoxylum binectariferum. When flavopiridol was first discovered, it was considered to be a tyrosine kinase antagonist but subsequently, it was shown to reversibly inhibit growth via inhibition of cyclin-dependent kinase (CDK)1 and CDK2[1, 2]. Flavopiridol induced cell cycle inhibition by altering phosphorylation of tyrosine residues as well as antagonizing CDK1 and CDK2 activity as a result of competitive inhibition with ATP[3]. Based on these initial observations, investigators hypothesized that flavopiridol would be effective in rapidly dividing tumor systems where a minimum volume of tumor exists. We now know that flavopiridol has a number of additional targets that include the cyclin D-1 complex over-expressed in mantle cell lymphoma and cyclin H. In addition, studies in lymphoma cell lines have demonstrated activity against activated B-cell (ABC) type cell lines and NF-kappa B down-regulation[4, 5].
