Purvalanol B

Purvalanol B is a selective inhibitor of CDK1, CDK2 and CDK4.
CDKs (cyclin-dependent kinases) family has the ability to regulate cell cycle.
Purvalanol B is reported as one of the most potent and selective CDK inhibitors. When tested with Chinese hamster lung fibroblast CCL39 cell line, treatment with Purvalanol B inhibited cells proliferate via targeting CKD1 which induced a G2/M block with a GI50 of 2.5 μM. In asynchronous cells, exposed to Purvalanol B led to an accumulation of cells in G2/M phase [1].
In a mouse model with NCI-H2228 subcutaneous xenograft, oral administration of ASP3026 caused significant reduction of phosphorylated ALK and tumor growth. 30 mg/kg/d ASP3026 for 2 weeks induced tumor regression by 78%. In mice injected with Karpas 299 cells, ASP3026 treatment caused remarkable lymphoma regression [2, 3].
Purvalanol B also interacts with p42/p44 MAPK proteins when tested with several mammalian cell lines including MCF-7 cell line [1].
References:
1.Kuromitsu S, Mori M, Shimada I, et al. Anti-tumor activity of ASP3026, a novel and selective ALK inhibitor of anaplastic lymphoma kinase (ALK). Annual Meeting of the American Association for Cancer Research (AACR), Orlando, FL. 2011.
2.Mori M, Ueno Y, Konagai S, et al. The Selective Anaplastic Lymphoma Receptor Tyrosine Kinase Inhibitor ASP3026 Induces Tumor Regression and Prolongs Survival in Non–Small Cell Lung Cancer Model Mice. Molecular cancer therapeutics, 2014, 13(2): 329-340.
3.George S K, Vishwamitra D, Manshouri R, et al. The ALK inhibitor ASP3026 eradicates NPM-ALK+ T-cell anaplastic large-cell lymphoma in vitro and in a systemic xenograft lymphoma model. Oncotarget, 2014, 5(14): 5750-5763.

VMY-1-103, a dansylated analog of purvalanol B, induces caspase-3-dependent apoptosis in LNCaP prostate cancer cells.[Pubmed:20574155]

Cancer Biol Ther. 2010 Aug 15;10(4):320-5. Epub 2010 Aug 3.

The 2,6,9-trisubstituted purine group of cyclin dependent kinase inhibitors have the potential to be clinically relevant inhibitors of cancer cell proliferation. We have recently designed and synthesized a novel dansylated analog of Purvalanol B, termed VMY-1-103, that inhibited cell cycle progression in breast cancer cell lines more effectively than did Purvalanol B and allowed for uptake analyses by fluorescence microscopy. ErbB-2 plays an important role in the regulation of signal transduction cascades in a number of epithelial tumors, including prostate cancer (PCa). Our previous studies demonstrated that transgenic expression of activated ErbB-2 in the mouse prostate initiated PCa and either the overexpression of ErbB-2 or the addition of the ErbB-2/ErbB-3 ligand, heregulin (HRG), induced cell cycle progression in the androgen-responsive prostate cancer cell line, LNCaP. In the present study, we tested the efficacy of VMY-1-103 in inhibiting HRG-induced cell proliferation in LNCaP prostate cancer cells. At concentrations as low as 1 muM, VMY-1-103 increased both the proportion of cells in G(1) and p21(CIP1) protein levels. At higher concentrations (5 muM or 10 muM), VMY-1-103 induced apoptosis via decreased mitochondrial membrane polarity and induction of p53 phosphorylation, caspase-3 activity and PARP cleavage. Treatment with 10 muM Purvalanol B failed to either influence proliferation or induce apoptosis. Our results demonstrate that VMY-1-103 was more effective in inducing apoptosis in PCa cells than its parent compound, Purvalanol B, and support the testing of VMY-1-103 as a potential small molecule inhibitor of prostate cancer in vivo.

Effects of cyclin-dependent kinase inhibitor Purvalanol B application on protein expression and developmental progression in intra-erythrocytic Plasmodium falciparum parasites.[Pubmed:25879664]

Malar J. 2015 Apr 8;14:147.

BACKGROUND: The 2013 Malaria World Report indicated that in 2012 there were approximately 207 million cases of malaria, which resulted in an estimated 627,000 malaria-related deaths. Due to the alarming resistance of these parasites to traditional anti-malarial treatments there is a pressing need to not only identify new anti-malarial compounds, but also to characterize the effect of compounds known to have an effect on the parasite life cycle. This study reports on effects of kinase inhibitor Purvalanol B administration on the growth and protein expression of Plasmodium falciparum late-stage trophozoites. METHODS: A SYBR(R) Green I parasite growth assay was used to measure the IC50 of Purvalanol B with P. falciparum (strain W2). Purvalanol B or DMSO control were applied to synchronized parasites 36 hours post invasion and parasites were incubated for 12 hours. Giemsa-stained blood smears were used to determine the effect of Purvalanol B on parasite growth, global quantitative proteomic analysis was used to examine differences in protein expression between Purvalanol B-treated and control parasites and results were confirmed by qPCR. RESULTS: There were no differences in parasitaemia between inhibitor-treated and control parasites. However, the ability of Purvalanol B-treated parasites to form schizonts was significantly reduced. Proteomic analysis detected 76 human proteins and 518 P. falciparum proteins (63 in control cultures only, 56 proteins in Purvalanol B cultures only, and 399 proteins in both cultures). Quantitative analysis of protein extracts revealed eight proteins that were up-regulated in the inhibitor-treated cultures, including several components of the parasite's proteasome complex and thioredoxin reductase. Two proteins appeared to be down-regulated, including a helicase and an RNA-binding protein. CONCLUSION: Purvalanol B application decreases the ability of late-stage P. falciparum trophozoites to form multinucleated schizonts and up-regulates proteasome subunits and proteins that contribute to redox homeostasis, which may indicate an increase in oxidative stress as a result of inhibitor application. While the efficacy of Purvalanol B is relatively low for use as an anti-malarial therapy, quantitative proteomic analysis may serve as a method of examining the action of drugs on the parasite and indicate the likelihood of future resistance development.

p42/p44 MAPKs are intracellular targets of the CDK inhibitor purvalanol.[Pubmed:12226745]

Oncogene. 2002 Sep 19;21(42):6413-24.

Chemical inhibitors of cyclin-dependent kinases (CDKs) have a great therapeutic potential against various proliferative and neurodegenerative disorders. Intensive screening of a combinatorial chemistry library of 2,6,9-trisubstituted purines has led to the identification of purvalanol, one of the most potent and selective CDK inhibitors to date. In preliminary studies, this compound demonstrates definite anti-mitotic properties, consistent with its nanomolar range efficiency towards purified CDK1 and CDK2. However, the actual intracellular targets of purvalanol remain to be identified, and a method for the determination of its in vivo selectivity was developed. In this technique, cell extracts were screened for purvalanol-interacting proteins by affinity chromatography on immobilized inhibitor. In addition to CDK1, p42/p44 MAPK were found to be two major purvalanol-interacting proteins in five different mammalian cell lines (CCL39, PC12, HBL100, MCF-7 and Jurkat cells), suggesting the generality of the purvalanol/p42/p44 MAPK interaction. The Chinese hamster lung fibroblast cell line CCL39 was used as a model to investigate the anti-proliferative properties of purvalanol. The compound inhibited cell growth with a GI(50) value of 2.5 microM and induced a G2/M block when added to exponentially growing cells. It did not appear to trigger massive activation of caspase. We next tested whether CDKs and p42/p44 MAPK were actually targeted by the compound in vivo. p42/p44 MAPK activity was visualized using an Elk-Gal4 luciferase reporter system and CDK1 activity was detected by the phosphonucleolin level. When cells were treated with purvalanol, p42/p44 MAPK and CDK1 activities were inhibited in a dose-dependent manner. Furthermore, purvalanol inhibited the nuclear accumulation of p42/p44 MAPK, an event dependent on the catalytic activity of these kinases. We conclude that the anti-proliferative properties of purvalanol are mediated by inhibition of both p42/p44 MAPK and CDKs. These observations highlight the potency of moderate selectivity compounds and encourage the search for new therapeutics which simultaneously target distinct but relevant pathways of cell proliferation.

ATP-site directed inhibitors of cyclin-dependent kinases.[Pubmed:10495356]

Curr Med Chem. 1999 Sep;6(9):859-75.

Cyclin-dependent kinases trigger and coordinate transitions between different phases the cell division cycle (CDK1, 2, 3, 4, 6, 7). They also play a role in apoptosis (CDK2), in neuronal cells (CDK5) and in the control of transcription (CDK 7, 8, 9). Intensive screening has lead to the recent identification of a series of chemical inhibitors of CDKs: olomoucine, roscovitine, purvalanol, CVT-313, flavopiridol, g-butyrolactone, indirubins, paullones and staurosporine. Some of these compounds display remarkable selectivities and efficiencies (IC50 < 25 nM). Many have been co-crystallised with CDK2 and their interactions with the kinase have been analysed in atomic detail. These inhibitors all act by competing with ATP for binding at the catalytic site. Most inhibitors present a flat heterocyclic ring system that occupies the purine binding pocket as well as form 2 or 3 hydrogen bonds with Glu-81 and Leu-83. The binding modes of these inhibitors are reviewed in this article. Knowledge of the CDK/inhibitor interactions will be of great help to design inhibitors with improved selectivity our potency as well as to generate affinity chromatography matrices for the purification and identification of their cellular targets. The potential use of CDK inhibitors is being extensively evaluated in cancer chemotherapy and other fields such as the cardiovascular domain (restenosis), dermatology (psoriasis), nephrology (glomerulonephritis) parasitology (unicellular parasites such as Plasmodium, Trypanosomes, Toxoplasm,.etc.), neurology (Alzheimer's disease) and viral infections (cytomegalovirus, H.I.V., herpes).

Exploiting chemical libraries, structure, and genomics in the search for kinase inhibitors.[Pubmed:9677190]

Science. 1998 Jul 24;281(5376):533-8.

Selective protein kinase inhibitors were developed on the basis of the unexpected binding mode of 2,6,9-trisubstituted purines to the adenosine triphosphate-binding site of the human cyclin-dependent kinase 2 (CDK2). By iterating chemical library synthesis and biological screening, potent inhibitors of the human CDK2-cyclin A kinase complex and of Saccharomyces cerevisiae Cdc28p were identified. The structural basis for the binding affinity and selectivity was determined by analysis of a three-dimensional crystal structure of a CDK2-inhibitor complex. The cellular effects of these compounds were characterized in mammalian cells and yeast. In the latter case the effects were characterized on a genome-wide scale by monitoring changes in messenger RNA levels in treated cells with high-density oligonucleotide probe arrays. Purine libraries could provide useful tools for analyzing a variety of signaling and regulatory pathways and may lead to the development of new therapeutics.

Purvalanol B(NG-95) is a cyclin-dependent kinase inhibitor with IC50 values of 6, 6, 9, > 10,000, and 6 nM for cdc2/cyclin B, cdk2/cyclin A, cdk2/cyclin E, cdk4/cyclin D1 and cdk5-p35 respectively.

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