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A series of novel [3a,4]dihydropyrazolo[1,5a]pyrimidines were identified, which were highly potent and selective inhibitors of PI3Kβ. The template afforded the opportunity to develop novel SAR for both the hinge-binding (R3) and back-pocket (R4) substitutents. While cellular potency was relatively modest due to high protein binding, the series displayed low clearance in rat, mouse, and monkey.

Several multikinase angiogenesis inhibitors demonstrate mitochondrial and/or cardiovascular toxicity, suggesting an on-target pharmacologic effect. To evaluate whether cardiotoxicity is directly related to vascular endothelial growth factor receptor inhibition, we investigated the effects of sunitinib, sorafenib, and pazopanib on myocardial function and structure. We used a rat model to assess myocardial effects of the inhibitors concurrently exposed to the cardiac stressor dobutamine. Echocardiographic abnormalities including premature ventricular contractions, decreases in heart rate, circumferential strain, and radial and circumferential strain rates were noted with sorafenib, but not with sunitinib or pazopanib. Ultrastructural analysis of ventricular cardiomyocytes by transmission electron microscopy revealed mitochondrial swelling, dense deposits, and matrix cavitation in rats given sunitinib and disrupted mitochondrial cristae in rats given sorafenib, but there were no effects with pazopanib. Effects on neonatal rat cardiomyocyte cultures were assessed, which identified decreases in mitochondrial membrane potential with sunitinib treatment, but not with sorafenib or pazopanib. Intracellular adenosine triphosphate depletion was observed with sunitinib and sorafenib, but not pazopanib. Our results show that cardiotoxicity is not necessarily related to a pharmacologic classwide effect of vascular endothelial growth factor receptor inhibition, and the rat myocardial structural and functional changes identified in this study may be instead a result of inhibition of other kinase pathways, the mechanism of which may be associated with mitochondrial toxicity.

A novel thiazolopyrimidinone series of PI3K-beta selective inhibitors has been identified. This chemotype has provided an excellent tool compound, 18, that showed potent growth inhibition in the PTEN-deficient breast cancer cell line MDA-MB-468 under anchorage-independent conditions, and it also demonstrated pharmacodynamic effects and efficacy in a PTEN-deficient prostate cancer PC-3 xenograft mouse model.

Many cancer cells generate energy by rapidly converting glucose to lactate in the cytosol, a process termed aerobic glycolysis. This metabolic phenotype is recognized as one of the hallmarks of cancer and is enabled by lactate dehydrogenase (LDH), which catalyzes pyruvate to lactate inter-conversion. We find that hepatocellular carcinoma cells express micromolar quantities of LDH5 and that LDH5 protein down-regulation takes about 5 days allowing time for the cells to adapt their metabolism. Since metabolic processes happen in minutes, addressing consequences of LDH5 inhibition by protein down-regulation is inadequate. We screened the GSK compound library and identified a series of quinoline acids as NADH-competitive LDH5 inhibitors. Subsequent lead optimization yielded molecules with LDH5 inhibitory potencies as low as 2-3 nM and selectivity over LDH1 on the order of 10-100-fold. These molecules were cell-permeable and did not have any appreciable activity against a panel of approximately fifty common enzymes, receptors and ion channels, making them the most potent and selective LDH5 inhibitors identified to date. Using these tool inhibitors, we find that rapid chemical inhibition of LDH5 in Snu398 hepatocellular carcinoma cells results in profound inhibition of lactate production and increase in pyruvate as measured by mass spectrometric analysis. Real-time analysis by NMR spectroscopy of live Snu398 cells fed with 13C-labeled glucose demonstrated that chemical LDH5 inhibition led to a rapid decrease in glucose uptake and concomitant slow-down of lactate production. Comprehensive analysis of more than 500 metabolites upon LDH5 inhibition in Snu398 cells revealed that the cytosolic glycolysis pathway was significantly impeded with some up-stream intermediates increasing as much as 40-fold. As the cell lost its ability for cytosolic glucose processing, the TCA cycle activity increased indicating that pyruvate entered the mitochondria and restored their activity resulting in increased oxygen consumption upon LDH5 inhibition. Several pathways that rely on glycolytic and TCA intermediates were also upregulated, including fatty acid metabolism and pentose phosphate pathway. LDH5 inhibition also strongly potentiated PKM2 activity. These profound metabolic alterations greatly impaired cell survival and induced cell death in Snu398 cells. In summary, we have shown that rapid chemical inhibition of LDH5 leads to profound metabolic alterations and impairs cell survival in hepatocellular carcinoma cells making it a compelling strategy for treating solid tumors relying on aerobic glycolysis. Citation Format: Julia Billiard, Roland Annan, Jennifer Ariazi, Jacques Briand, Kristin Brown, Nino Campobasso, Subhas Chakravorty, Deping Chai, Mariela Colón, Elizabeth Davenport, Christopher Dodson, Nathan Gaul, Seth Gilbert, Anthony Jurewicz, Hong Lu, Dean McNulty, Jeanelle McSurdy-Freed, Lisa Miller, Kelvin Nurse, Paru Rao Nuthulaganti, Chad Quinn, Jessica Schneck, Gilbert Scott, Tony Shaw, Christian Sherk, Angela Smallwood, Sharon Sweitzer, James Villa, Gregory Waitt, Richard Wooster, Kevin Duffy. Rapid LDH5 inhibition reverses malignant metabolic phenotype and impairs survival of hepatocellular carcinoma cells . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5418. doi:10.1158/1538-7445.AM2013-5418

Background Most normal cells in the presence of oxygen utilize glucose for mitochondrial oxidative phosphorylation. In contrast, many cancer cells rapidly convert glucose to lactate in the cytosol, a process termed aerobic glycolysis. This glycolytic phenotype is enabled by lactate dehydrogenase (LDH), which catalyzes the inter-conversion of pyruvate and lactate. The purpose of this study was to identify and characterize potent and selective inhibitors of LDHA. Methods High throughput screening and lead optimization were used to generate inhibitors of LDHA enzymatic activity. Effects of these inhibitors on metabolism were evaluated using cell-based lactate production, oxygen consumption, and 13C NMR spectroscopy assays. Changes in comprehensive metabolic profile, cell proliferation, and apoptosis were assessed upon compound treatment. Results 3-((3-carbamoyl-7-(3,5-dimethylisoxazol-4-yl)-6-methoxyquinolin-4-yl) amino) benzoic acid was identified as an NADH-competitive LDHA inhibitor. Lead optimization yielded molecules with LDHA inhibitory potencies as low as 2 nM and 10 to 80-fold selectivity over LDHB. Molecules in this family rapidly and profoundly inhibited lactate production rates in multiple cancer cell lines including hepatocellular and breast carcinomas. Consistent with selective inhibition of LDHA, the most sensitive breast cancer cell lines to lactate inhibition in hypoxic conditions were cells with low expression of LDHB. Our inhibitors increased rates of oxygen consumption in hepatocellular carcinoma cells at doses up to 3 microM, while higher concentrations directly inhibited mitochondrial function. Analysis of more than 500 metabolites upon LDHA inhibition in Snu398 cells revealed that intracellular concentrations of glycolysis and citric acid cycle intermediates were increased, consistent with enhanced Krebs cycle activity and blockage of cytosolic glycolysis. Treatment with these compounds also potentiated PKM2 activity and promoted apoptosis in Snu398 cells. Conclusions Rapid chemical inhibition of LDHA by these quinoline 3-sulfonamids led to profound metabolic alterations and impaired cell survival in carcinoma cells making it a compelling strategy for treating solid tumors that rely on aerobic glycolysis for survival.