Suresh Kerwar

CVT-313, a Specific and Potent Inhibitor of CDK2 That Prevents Neointimal Proliferation

The activity of cyclin-dependent kinase 2 (CDK2) is essential for progression of cells from G1 to the S phase of the mammalian cell cycle. CVT-313 is a potent CDK2 inhibitor, which was identified from a purine analog library with an IC50 of 0.5 μm in vitro. Inhibition was competitive with respect to ATP (K i = 95 nm), and selective CVT-313 had no effect on other, nonrelated ATP-dependent serine/threonine kinases. When added to CDK1 or CDK4, a 8.5- and 430-fold higher concentration of CVT-313 was required for half-maximal inhibition of the enzyme activity. In cells exposed to CVT-313, hyperphosphorylation of the retinoblastoma gene product was inhibited, and progression through the cell cycle was arrested at the G1/S boundary. The growth of mouse, rat, and human cells in culture was also inhibited by CVT-313 with the IC50 for growth arrest ranging from 1.25 to 20 μm. To evaluate the effects of CVT-313 in vivo, we tested this agent in a rat carotid artery model of restenosis. A brief intraluminal exposure of CVT-313 to a denuded rat carotid artery resulted in more than 80% inhibition of neointima formation. These observations suggest that CVT-313 is a promising candidate for evaluation in other disease models related to aberrant cell proliferation.

Synthesis and activity of 2,6,9-trisubstituted purines

The preparation of a series of 2,6,9-trisubstituted purines and the structure-activity data for the inhibition of cyclin dependent kinase, CDK2 are presented.

A New Structural Class of Proteasome Inhibitors that Prevent NF-κB Activation

Abstract The multicatalytic proteinase or proteasome is a highly conserved cellular structure that is responsible for the ATP-dependent proteolysis of many proteins involved in important regulatory cellular processes. We have identified a novel class of inhibitors of the chymotrypsin-like proteolytic activity of the 20S proteasome that exhibit ic 50 values ranging from 0.1 to 0.5 μg/mL (0.1 to 1 μM). In cell proliferation assays, these compounds inhibit growth with an ic 50 ranging from 5 to 10 μg/mL (10–20 μM). A representative member of this class of inhibitors was tested in other biological assays. CVT-634 (5-methoxy-1-indanone-3-acetyl-leu- d -leu-1-indanylamide) prevented lipopolysaccharide (LPS), tumor necrosis factor (TNF)-, and phorbol ester-induced activation of nuclear factor κB (NF-κB) in vitro by preventing signal-induced degradation of IκB-α. In these studies, the IκB-α that accumulated was hyperphosphorylated, indicating that CVT-634 did not inhibit IκB-α kinase, the enzyme responsible for signal-induced phosphorylation of IκB-α. In vivo studies indicated that CVT-634 prevented LPS-induced TNF synthesis in a murine macrophage cell line. In addition, in mice pretreated with CVT-634 at 25 and 50 mg/kg and subsequently treated with LPS, serum TNF levels were significantly lower (225 ± 59 and 83 ± 41 pg/mL, respectively) than in those mice that were treated only with LPS (865 ± 282 pg/mL). These studies suggest that specific inhibition of the chymotrypsin-like activity of the proteasome is sufficient to prevent signal-induced NF-κB activation and that the proteasome is a novel target for the identification of agents that may be useful in the treatment of diseases whose etiology is dependent upon the activation of NF-κB.