Yogesh A. Sonawane

Cyclin-dependent kinase 9 (CDK9), a member of the cyclin-dependent protein kinase (CDK) family, is involved in transcriptional elongation of several target genes. CDK9 is ubiquitously expressed and has been shown to contribute to a variety of malignancies such as pancreatic, prostate and breast cancers. Here we report the development of a heterobifunctional small molecule proteolysis targeting chimera (PROTAC) capable of cereblon (CRBN) mediated proteasomal degradation of CDK9. In HCT116 cells, it selectively degrades CDK9 while sparing other CDK family members. This is the first example of a PROTAC that selectively degrades CDK9.

Cyclin dependent kinase (CDK) inhibitors have been the topic of intense research for nearly 2 decades due to their widely varied and critical functions within the cell. Recently CDK9 has emerged as a druggable target for the development of cancer therapeutics. CDK9 plays a crucial role in transcription regulation; specifically, CDK9 mediated transcriptional regulation of short-lived antiapoptotic proteins is critical for the survival of transformed cells. Focused chemical libraries based on a plethora of scaffolds have resulted in mixed success with regard to the development of selective CDK9 inhibitors. Here we review the regulation of CDK9, its cellular functions, and common core structures used to target CDK9, along with their selectivity profile and efficacy in vitro and in vivo.

Novel Y-shaped acceptor-pi-donor-pi-acceptor-type compounds, synthesized from 4,4'-hexyliminobisbenzaldehyde as electron donors and different active methylene compounds as electron acceptors, were produced by conventional Knoevenagel condensation alone, with a deep eutectic solvent, or with a lipase biocatalyst to compare the yield and recyclability among the three methods. Yield, reaction time, reaction temperature, and recyclability were compared among the three methods. The photophysical properties and thermal stability of the products were also investigated.

// Caroline M. Robb 1 , Smit Kour 1 , Jacob I. Contreras 1 , Ekta Agarwal 1 , Carter J. Barger 1 , Sandeep Rana 1 , Yogesh Sonawane 1 , Beth K. Neilsen 1 , Margaret Taylor 1 , Smitha Kizhake 1 , Rhishikesh N. Thakare 2 , Sanjib Chowdhury 3 , Jing Wang 1, 4 , Jennifer D. Black 1, 4 , Michael A. Hollingsworth 1, 4 , Michael G. Brattain 1, 4, * and Amarnath Natarajan 1, 2, 4 1 Eppley Institute for Research in Cancer, University of Nebraska Medical Center, 985950 Nebraska Medical Center, Omaha, Nebraska 68198-5950, USA 2 Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950, USA 3 Section of Gastroenterology, Department of Medicine, Boston University Medical Center, Boston, Massachusetts 02118, USA 4 Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950, USA * Deceased Correspondence to: Amarnath Natarajan, email: anatarajan@unmc.edu Keywords: colorectal cancer (CRC); cyclin-dependent kinase (CDK); CDK inhibitor Received: September 06, 2017      Accepted: November 10, 2017      Published: December 28, 2017 ABSTRACT Colorectal cancer (CRC) remains one of the leading causes of cancer related deaths in the United States. Currently, there are limited therapeutic options for patients suffering from CRC, none of which focus on the cell signaling mechanisms controlled by the popular kinase family, cyclin dependent kinases (CDKs). Here we evaluate a Pfizer developed compound, CP668863, that inhibits cyclin-dependent kinase 5 (CDK5) in neurodegenerative disorders. CDK5 has been implicated in a number of cancers, most recently as an oncogene in colorectal cancers. Our lab synthesized and characterized CP668863 – now called 20-223. In our established colorectal cancer xenograft model, 20-223 reduced tumor growth and tumor weight indicating its value as a potential anti-CRC agent. We subjected 20-223 to a series of cell-free and cell-based studies to understand the mechanism of its anti-tumor effects. In our hands, in vitro 20-223 is most potent against CDK2 and CDK5. The clinically used CDK inhibitor AT7519 and 20-223 share the aminopyrazole core and we used it to benchmark the 20-223 potency. In CDK5 and CDK2 kinase assays, 20-223 was ~3.5-fold and ~65.3-fold more potent than known clinically used CDK inhibitor, AT7519, respectively. Cell-based studies examining phosphorylation of downstream substrates revealed 20-223 inhibits the kinase activity of CDK5 and CDK2 in multiple CRC cell lines. Consistent with CDK5 inhibition, 20-223 inhibited migration of CRC cells in a wound-healing assay. Profiling a panel of CRC cell lines for growth inhibitory effects showed that 20-223 has nanomolar potency across multiple CRC cell lines and was on an average >2-fold more potent than AT7519. Cell cycle analyses in CRC cells revealed that 20-223 phenocopied the effects associated with AT7519. Collectively, these findings suggest that 20-223 exerts anti-tumor effects against CRC by targeting CDK 2/5 and inducing cell cycle arrest. Our studies also indicate that 20-223 is a suitable lead compound for colorectal cancer therapy.

Over expression of 11β-HSD 1 in key metabolic tissues is related to the development of type 2 diabetes, obesity, hypertension and metabolic syndrome. Nephrotoxicity of corosolic acid (selective inhibitor of 11β-HSD 1) is recently reported, which is one of the major drawback. Therefore, it is of great interest to find out the selective 11β-HSD 1 inhibitors without nephrotoxicity. Using crystal structures of 11β-HSD 1 in complex with inhibitors as a source of structural information, a combined structure-based virtual screening approach followed by PASS toxicity prediction, Lipinski’s rule and ADME prediction was implemented to find out the potent and selective 11 β-HSD 1 analog of corosolic acid without nephrotoxicity. Two compounds with NCBI compound identification number CID59752459 (Genins of Asiatic acid) and CID 119034 (Asiatic acid) were found to be selective for the 11β-HSD 1 enzyme without nephrotoxicity which comply with Lipinski’s rule and ADME parameter defined for human use. However, none of the hits inhibited 11β-HSD 2 at 100 μM indicating their selectivity against 11β-HSD 1.