Michael Saunders

Epigenetic Drug Discovery Targeting DNA Methyltransferases

Epigenetic modification of DNA leads to changes in gene expression. DNA methyltransferases (DNMTs) comprise a family of nuclear enzymes that catalyze the methylation of CpG dinucleotides, resulting in an epigenetic methylome distinguished between normal cells and those in disease states such as cancer. Disrupting gene expression patterns through promoter methylation has been implicated in many malignancies and supports DNMTs as attractive therapeutic targets. This review focuses on the rationale of targeting DNMTs in cancer, the historical approach to DNMT inhibition, and current marketed hypomethylating therapeutics azacytidine and decitabine. In addition, we address novel DNMT inhibitory agents emerging in development, including CP-4200 and SGI-110, analogs of azacytidine and decitabine, respectively; the oligonucleotides MG98 and miR29a; and a number of reversible inhibitors, some of which appear to be selective against particular DNMT isoforms. Finally, we discuss future opportunities and challenges for next-generation therapeutics.

Pharmacologic Activation of PKM2 Slows Lung Tumor Xenograft Growth

Inactivation of the M2 form of pyruvate kinase (PKM2) in cancer cells is associated with increased tumorigenicity. To test the hypothesis that tumor growth may be inhibited through the PKM2 pathway, we generated a series of small-molecule PKM2 activators. The compounds exhibited low nanomolar activity in both biochemical and cell-based PKM2 activity assays. These compounds did not affect the growth of cancer cell lines under normal conditions in vitro, but strongly inhibited the proliferation of multiple lung cancer cell lines when serine was absent from the cell culture media. In addition, PKM2 activators inhibited the growth of an aggressive lung adenocarcinoma xenograft. These findings show that PKM2 activation by small molecules influences the growth of cancer cells in vitro and in vivo, and suggest that such compounds may augment cancer therapies. Mol Cancer Ther; 12(8); 1453–60. ©2013 AACR.

Triterpene based compounds with potent anti-maturation activity against HIV-1.

Efforts towards developing orally bioavailable HIV-1 maturation inhibitors starting from betulinic acid 1 are described. SAR resulted in improved potency, physicochemical properties, and enhanced oral absorption in rats.

Abstract 3762: Second generation PIM inhibitors exhibit improved activity in solid tumor models

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL The proto-oncogene PIM kinase family (PIM-1, -2 and -3) includes constitutively active serine/threonine kinases upregulated in multiple cancer indications, including lymphomas, leukemias, multiple myeloma, prostate and bladder cancers. Overexpression of one or more PIM family members in patient tumors frequently correlates with poor prognosis. The PIM kinases function by inhibiting apoptosis in MYC-driven tumors, and promoting tumor cell survival and proliferation. In the HEK-293T cell line, enhanced PIM kinase substrate BAD phosphorylation (pBAD) was observed following PIM and BAD overexpression. Enhancement of pBAD was inhibited by SGI-1776, a well-described PIM inhibitor, and more effectively by second generation PIM inhibitors exhibiting 4-10 fold improved potency against the PIM kinase family. The current PIM inhibitors display sub-µM activity in pharmacodynamic marker, proliferation and 2D colony formation assays using the UM-UC-3 human bladder cancer cell line. PIM1 and PIM2 overexpression models were established in the human prostate cancer cell line 22RV-1 and the non-tumorigenic mouse NIH-3T3 cell background. Overexpression of PIM kinases led to enhanced cell growth and tumorigenicity in both NIH-3T3 and 22RV-1 cell lines. In vivo xenograft studies using both PIM overexpression models and a clinically relevant solid tumor model facilitated identification of a lead candidate with demonstrated efficacy and favorable toxicity. IND-enabling studies with a lead candidate are underway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3762. doi:1538-7445.AM2012-3762

Abstract C200: Second-generation PIM inhibitors exhibit improved activity in solid tumor models in vitro.

The proto-oncogene PIM kinase family (PIM-1, -2 and -3) comprises constitutively active serine/threonine kinases upregulated in multiple cancer indications, including lymphoma, leukemia, multiple myeloma, prostate, bladder, gastric and head & neck cancers. Overexpression of one or more PIM family members in patient tumors frequently correlates with poor prognosis. The PIM kinases function by inhibiting apoptosis in MYC-driven tumors, promoting tumor cell survival and proliferation. PIM-1 and PIM-2 overexpression models were obtained in the human prostate cancer cell lines PC-3M and 22RV-1 and the non-tumorigenic mouse NIH-3T3 background. Overexpression of PIM kinases led to enhanced cell growth and tumorigenicity in both NIH-3T3 and 22RV-1 cell lines. In the PC-3M cell line, enhanced phosphorylation of the PIM kinase substrate BAD (pBAD) was observed following PIM overexpression. Enhancement of pBAD was inhibited by SGI-1776, a well-described PIM inhibitor, as well as next generation PIM inhibitors exhibiting 4–10 fold improved potency against the PIM kinase family. The current PIM inhibitors display sub-μM activity in pharmacodynamic marker, proliferation and 2D colony formation assays using the PC-3M prostate cancer cell line, the UM-UC-3 bladder cancer cell line, and the HSC3 head & neck cancer cell line. The second generation PIM inhibitors possess favorable hERG and CYP inhibition profiles compared with SGI-1776, and demonstrate excellent oral bioavailability. In vivo xenograft studies using both PIM overexpression models and clinically relevant solid tumor models will facilitate identification of a clinical candidate. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C200.

Abstract 3226: PKM2 metabolic activator slows lung cancer xenograft growth

Tumor cells primarily utilize aerobic glycolysis, rather than oxidative phosphorylation, to metabolize glucose (the Warburg effect). The M2 splice form of pyruvate kinase (PKM2), the enzyme catalyzing the rate-limiting final step of glycolysis, is highly upregulated in tumors. Unlike the M1 splice form (PKM1), a constitutively active tetramer found predominantly in non-cancerous tissues, PKM2 is an inactive dimer under normal physiological conditions. Tetramerization of PKM2 requires binding of the allosteric activator fructose-1,6-bisphosphate (FBP), an upstream glycolytic intermediate, resulting in a fully active enzyme. Inactivation of PKM2 by cancer cells may allow glycolytic intermediates to be diverted into other biosynthetic pathways necessary for biomass production. The finding that PKM2 rather than PKM1 expression enhances tumorigenicity suggests that activators of PKM2 may have anti-tumor properties. We have identified and developed a series of small molecule PKM2 activators that exhibit low nM activation activity in biochemical and cell-based assays that measure pyruvate and ATP production. The extent of activation of these compounds is equal to or greater than that of FBP in biochemical assays. In addition, preliminary studies show that PKM2 activators inhibit the growth of lung cancer cell lines in vitro. The current lead compound was tested in established subcutaneously implanted A549 lung adenocarcinoma xenografts, where we observed a statistically significant decrease in tumor growth, with no observable toxicity. These data suggest that this class of PKM2 activators is effective as tumor cell metabolic regulators with anti-tumor activity for lung cancer and potentially other malignancies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3226. doi:1538-7445.AM2012-3226

Abstract B143: PKM2 metabolic activator slows lung cancer xenograft growth.

Tumor cells primarily utilize aerobic glycolysis, rather than oxidative phosphorylation, to metabolize glucose (the Warburg effect). The M2 splice form of pyruvate kinase (PKM2), the enzyme catalyzing the rate-limiting final step of glycolysis, is highly upregulated in tumors. Unlike the M1 splice form (PKM1), a constitutively active tetramer found predominantly in non-cancerous tissues, PKM2 is an inactive dimer under normal physiological conditions. Tetramerization of PKM2 requires binding of the allosteric activator fructose-1,6-bisphosphate (FBP), an upstream glycolytic intermediate, resulting in a fully active enzyme. Inactivation of PKM2 by cancer cells may allow glycolytic intermediates to be diverted into other biosynthetic pathways necessary for biomass production. The finding that PKM2 rather than PKM1 expression enhances tumorigenicity suggests that activators of PKM2 may have anti-tumor properties. We have identified and developed a series of small molecule PKM2 activators that exhibit low nM activation activity in biochemical and cell-based assays that measure pyruvate and ATP production. The extent of activation of these compounds is equal to or greater than that of FBP in biochemical assays. In addition, preliminary studies show that PKM2 activators inhibit the growth of lung cancer cell lines in vitro. The current lead compound was tested in established subcutaneously implanted A549 lung adenocarcinoma xenografts, where we observed a statistically significant 54% decrease in tumor growth, with no observable toxicity. These data suggest that this class of PKM2 activators is effective as tumor cell metabolic regulators with anti-tumor activity for lung cancer and potentially other malignancies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B143.