alvocidib and dinaciclib

CDK9 is a protein in constant development in cancer therapy. Herein we present an overview of the enzyme as a target for cancer therapy. We provide data on its characteristics and mechanism of action. In recent years, CDK9 inhibitors that have been designed with molecular modeling have demonstrated good antitumoral activity in vitro. Clinical studies of the drugs flavopiridol, dinaciclib, seliciclib, SNS-032 and RGB-286638 used as CDK9 inhibitors are also reviewed, with their additional targets and their relative IC50 values. Unfortunately, treatment with these drugs remains unsuccessful and involves many adverse effects. We could conclude that there are many small molecules that bind to CDK9, but their lack of selectivity against other CDKs do not allow them to get to the clinical use. However, drug designers currently have the tools needed to improve the selectivity of CDK9 inhibitors and to make successful treatment available to patients.

Topics: Bridged Bicyclo Compounds, Heterocyclic; Cell Cycle; Cyclic N-Oxides; Cyclin-Dependent Kinase 9; Flavonoids; Humans; Indolizines; Molecular Targeted Therapy; Neoplasms; Oxazoles; Piperidines; Protein Kinase Inhibitors; Purines; Pyrazoles; Pyridinium Compounds; Roscovitine; Thiazoles; Urea

Half of a century ago, physicians managing chronic lymphocytic leukemia (CLL) recognized some of its presenting features such as lymphocytosis, lymphadenopathy, and splenomegaly. Subsequently, an enhanced understanding of the disease mechanisms involved in CLL led to new, more targeted treatments. There is now a plethora of treatments available for CLL. In this review article we discuss in detail several of the novel agents that are being studied or approved for the treatment of CLL including: phosphatidylinositol 3-kinase inhibitors (idelalisib and IPI-145), Bruton tyrosine kinase inhibitors (ibrutinib), B cell lymphoma 2 inhibitors (ABT-263 and ABT-199), new anti-CD20 monoclonal antibodies (obinutuzumab), cyclin-dependent kinase inhibitors (flavopiridol and dinaciclib), immunomodulators (lenalidomide) and chimeric antigen receptor T-cell therapy.

Topics: Adenine; Aniline Compounds; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Bridged Bicyclo Compounds, Heterocyclic; Cyclic N-Oxides; Flavonoids; Humans; Immunologic Factors; Indolizines; Isoquinolines; Lenalidomide; Leukemia, Lymphocytic, Chronic, B-Cell; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-bcl-2; Purines; Pyrazoles; Pyridinium Compounds; Pyrimidines; Quinazolinones; Receptors, Antigen, T-Cell; Sulfonamides; Thalidomide

The t(8;21) is one of the most frequent chromosomal translocations associated with acute myeloid leukemia (AML). We found that t(8;21) AML were extremely sensitive to THZ1, which triggered apoptosis after only 4 h. We used precision nuclear run-on transcription sequencing (PROseq) to define the global effects of THZ1 and other CDK inhibitors on RNA polymerase II dynamics. Inhibition of CDK7 using THZ1 caused wide-spread loss of promoter-proximal paused RNA polymerase. This loss of 5' pausing was associated with accumulation of polymerases in the body of a large number of genes. However, there were modest effects on genes regulated by 'super-enhancers'. At the 3' ends of genes, treatment with THZ1 suppressed RNA polymerase 'read through' at the end of the last exon, which resembled a phenotype associated with a mutant RNA polymerase with slower elongation rates. Consistent with this hypothesis, polyA site-sequencing (PolyA-seq) did not detect differences in poly A sites after THZ1 treatment. PROseq analysis after short treatments with THZ1 suggested that these 3' effects were due to altered CDK7 activity at the 5' end of long genes, and were likely to be due to slower rates of elongation.

Topics: 3' Flanking Region; 5' Flanking Region; Antineoplastic Agents; Apoptosis; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Cell Proliferation; Cyclic N-Oxides; Cyclin-Dependent Kinase 9; Cyclin-Dependent Kinase-Activating Kinase; Cyclin-Dependent Kinases; Flavonoids; Gene Expression Regulation, Leukemic; Humans; Indolizines; Myeloid Cells; Phenylenediamines; Piperazines; Piperidines; Piperidones; Protein Kinase Inhibitors; Pyridines; Pyridinium Compounds; Pyrimidines; Pyrroles; RNA Polymerase II; Translocation, Genetic

To clarify the effects of cylcin E1 expression on HCC tumor progression, we studied the expression of cyclin E1 and inhibitory efficacy of regorafenib and sorafenib in HCC cells, and investigated a potential therapy that combines regorafenib treatment with cyclin E1 inhibition.. Western blotting for caspase-3 and Hoechst 33225 staining was used to measure the expression level of apoptosis-related proteins under drug treatment.. Our results showed that enhanced expression of cyclin E1 after transfection compromised apoptosis in HCC cells induced by regorafenib or sorafenib. Conversely, down-regulation of cyclin E1 gene expression or inhibition of cyclin E1 by the cyclin-dependent kinase (CDK) inhibitors dinaciclib (DIN) or flavopiridol sensitized HCC cells to regorafenib and sorafenib by inducing apoptosis. The expression of Mcl-1, which is modulated by STAT3, plays a key role in regulating the therapeutic effects of CDK inhibitors. Xenograft experiments conducted to test the efficacy of regorafenib combined with DIN showed dramatic tumor inhibitory effects due to induction of apoptosis. Our results suggested that the level of cyclin E1 expression in HCCs may be used as a pharmacodynamic biomarker to assess the antitumor effects of regorafenib or sorafenib.. Combining regorafenib and CDK inhibitors may enhance the clinical efficiency of the treatment of HCCs.

Topics: Animals; Apoptosis; Bridged Bicyclo Compounds, Heterocyclic; Carcinoma, Hepatocellular; Cell Line, Tumor; Cyclic N-Oxides; Cyclin E; Drug Synergism; Flavonoids; Gene Expression Regulation, Neoplastic; Humans; Indolizines; Liver Neoplasms; Male; Mice; Myeloid Cell Leukemia Sequence 1 Protein; Oncogene Proteins; Phenylurea Compounds; Piperidines; Prognosis; Pyridines; Pyridinium Compounds; Sorafenib; STAT3 Transcription Factor; Xenograft Model Antitumor Assays

The efficacy of many chemotherapeutic agents can be attenuated by expression of the anti-apoptotic proteins Bcl-2, Bcl-X(L) and Mcl-1. Flavopiridol and dinaciclib are cyclin-dependent kinase 7 and 9 inhibitors that transcriptionally inhibit expression of Mcl-1. We have investigated the ability of flavopiridol and dinaciclib to sensitize a panel of leukemia cell lines to vinblastine and paclitaxel. Both drugs acutely sensitized most of the leukemia lines to vinblastine, with 100% apoptosis in 4 h. Furthermore, dinaciclib sensitized freshly isolated chronic lymphocytic leukemia cells to vinblastine. This rapid induction of apoptosis was attributed to vinblastine-mediated activation of JNK because (a) flavopiridol and dinaciclib failed to induce apoptosis when combined with non-JNK activating concentrations of vinblastine; (b) JNK inhibitors suppressed JNK activity and prevented apoptosis; (c) flavopiridol did not potentiate apoptosis induced by paclitaxel which does not activate JNK in these cells; and (d) Jurkat cells failed to activate JNK in response to vinblastine and were not sensitive to combinations of vinblastine and flavopiridol or dinaciclib. The rapid induction of apoptosis by this combination in multiple cell systems but not in normal lymphocytes provides justification for performing a clinical trial to assess the efficacy in patients.

Topics: Anthracenes; Antineoplastic Agents, Phytogenic; Apoptosis; Bridged Bicyclo Compounds, Heterocyclic; Cell Cycle; Cell Line, Tumor; Cell Survival; Cyclic N-Oxides; Cyclin-Dependent Kinase 9; Cyclin-Dependent Kinase-Activating Kinase; Cyclin-Dependent Kinases; Dose-Response Relationship, Drug; Drug Synergism; Flavonoids; HL-60 Cells; Humans; Immunoblotting; Indolizines; JNK Mitogen-Activated Protein Kinases; Jurkat Cells; Myeloid Cell Leukemia Sequence 1 Protein; Paclitaxel; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-bcl-2; Pyridinium Compounds; U937 Cells; Vinblastine

Cyclin-dependent kinases (CDK) are key positive regulators of cell cycle progression and attractive targets in oncology. SCH 727965 inhibits CDK2, CDK5, CDK1, and CDK9 activity in vitro with IC(50) values of 1, 1, 3, and 4 nmol/L, respectively. SCH 727965 was selected as a clinical candidate using a functional screen in vivo that integrated both efficacy and safety parameters. Compared with flavopiridol, SCH 727965 exhibits superior activity with an improved therapeutic index. In cell-based assays, SCH 727965 completely suppressed retinoblastoma phosphorylation, which correlated with apoptosis onset and total inhibition of bromodeoxyuridine incorporation in >100 tumor cell lines of diverse origin and background. Moreover, short exposures to SCH 727965 were sufficient for long-lasting cellular effects. SCH 727965 induced regression of established solid tumors in a range of mouse models following intermittent scheduling of doses below the maximally tolerated level. This was associated with modulation of pharmacodynamic biomarkers in skin punch biopsies and rapidly reversible, mechanism-based effects on hematologic parameters. These results suggest that SCH 727965 is a potent and selective CDK inhibitor and a novel cytotoxic agent.

Topics: Antineoplastic Agents; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Cyclic N-Oxides; Cyclin-Dependent Kinases; Dose-Response Relationship, Drug; Flavonoids; Humans; Indolizines; Phosphorylation; Piperidines; Poly(ADP-ribose) Polymerases; Protein Kinase Inhibitors; Pyridinium Compounds; Retinoblastoma Protein; Xenograft Model Antitumor Assays