Abstract 3219: Changing the metabolism of cancer cells with PKM2 activators - a path to a cancer metabolism drug

Abstract

Pyruvate kinase (PK) M2 which catalyzes the last step in glycolysis, is the alternative spliced isoform expressed in cancer cells, and a key player in exerting the Warburg effect. One of the mechanisms by which PKM2 modulate cancer cell metabolism is by switching between the low activity monomer and the high activity tetramer forms. This process is controlled by the varying concentration of an upstream glycolytic intermediate, FBP. These changes enable the cancer cell to manage its usage of glucose carbon backbones, whether for ATP production or for biomass generation, according to its changing demands. Further, it has been recently shown that the elevated levels of ROS in cancer cells contribute to the decreased activity of PKM2 to support NADPH production to increase cellular anti-oxidation capacity to sustain proliferation. Our goal is to disrupt the metabolic adaptation of cancer cells with small molecule PKM2 modulators. We hypothesized that an activator will redirect the consumption of nutrients, especially of glucose, away from biomass production and ultimately send the cells to die. Using our proprietary structure-based technology, we identified several series of novel allosteric PKM2 activators. Chemical optimization resulted in potent compounds with AC50 as low as 10nM, which were selective against the other PK isoforms. These compounds were proven to stabilize the active tetramer form of PKM2 in cancer cells. Bioenergetic experiments in several cell lines demonstrated that not only do these agents reduce lactate production; they also reduce the oxygen consumption rate. Analysis of cell cycle showed that treatment with PKM2 activators causes the cells to arrest at the G1 phase. In outcome-based assays, these compounds significantly reduced the proliferation rate of various cancer cell lines, and this effect was sensitive to media conditions, such as glucose levels. Taken together, our data supports the hypothesis that activation of PKM2 effectively deprives the cancer cell of building blocks and reduces the detoxification capacity that are required to support growth and proliferation. An in vivo colorectal cancer HT29 cell line mouse xenograft model with a modestly active compound (IC50=0.9uM) demonstrated tumor growth inhibition greater than 50% (100 mg/kg Q2D and 200 and 400 mg/kg IP QD). The compound was very safe in mouse, even at the highest exposure levels (200 and 400 mg/kg IP QD), indicating that these efficacious doses are significantly lower than the MTD. Additional xenograft models are ongoing. Taken together, there is strong support for the effect of potent PKM2 small molecule activators on the cellular metabolism of cancer cells, demonstrating statistically significant anti-cancer effect in an animal model of colorectal cancer. The favorable DMPK profile of these compounds further supports their development as anti-proliferative agents, both as a single agent and in combination therapy. 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 3219. doi:1538-7445.AM2012-3219